Many an old idea originally seen as impossible, unpractical, or stupidly cranky, has become first possible, then obvious, then vitally, routinely, necessary. This has happened repeatedly throughout history and a good deal of prehistory, but as a trend it became especially obvious roughly at the time of the so-called industrial revolution. Significantly, the drive variously to ballyhoo or dismiss, disparage, and destroy novel advances remains as compulsive as ever.

Nearly every genuine advance, whether based on old ideas or new, encounters greater difficulties than expected, but also becomes more valuable in more contexts than expected.

And some are more vital than expected.

The idea of exploiting the planet's largest resources of fresh water, namely our great ice sheets, has been bruited and mocked for perhaps a century, but though it repeatedly has been dismissed as stupidly unrealistic, the simple fact is that it is unavoidable. We will be doing it, like it or lump it, on a scale hardly imagined by either proponent or opponent. People will make and lose fortunes, people will die of it, and people will make livings from it as routinely as sailors sail and technicians build and tend wind turbines and high-tension lines.

The question is whether we will establish an effective industry before we suffer serious global harm. History does not forbid us to hope, but it offers little positive reassurance.

For practical purposes this discussion ignores the harvesting of sea ice and glacial ice for the sake of luxury, fashion, science, or whim. It deals with the older, more prosaic, more visionary, idea of harvesting utility or irrigation water in bulk from sub-polar masses such as sea ice and icebergs. It emphatically does not suggest, I find it necessary to repeat at intervals, the towing of icebergs to where fresh water is needed. The idea of towing icebergs is so rooted in public fancy, that there is a tendency for readers to assume that it is necessarily the only option. That idea however, is grossly unpractical, for reasons that I wearily mention at several points, and that I reject accordingly.

As a serious suggestion the idea of iceberg corralling and towing dates back to at least the first half of the 20^th century, and it has met with understandable derision ever since. It certainly is no part of what I propose in this essay. However, my main reasons for rejection of the idea have to do with the nature of current needs for fresh water, and realities concerning its accessibility, its collection, its transport, and its processing. In part, the original reasons for rejection were firstly, that the bulk requirement for water in those days was smaller and less globally urgent, particularly among populations that had the resources and skills to contemplate such giant projects. And most nations had nothing of the type.

The very ideas that visionaries espoused for towing icebergs, genuinely were non-viable.

Also, until recently the very idea of a major city running dry seemed ludicrous and therefore could be ignored; parched third-world villages were irrelevant, largely because of their impotence. They still look irrelevant, and still largely because of their impotence. The poor in their local drought-stricken valleys or villages we have had with us always and we see no prospect of their disappearing.

What is more, before the last twenty years or so of the 20^th century the necessary technology for marine ice collection was not at a level that encouraged private enterprise to harvest ice for water; our shortcomings in the undeveloped technology for such purposes still are something of a challenge.

Another reason has been, and still is, our lack of any currently adequate infrastructure; one does not go out on a whim to collect billions of tonnes of water and transport them thousands of kilometres, simply relying on the principle of: "what could possibly go wrong?"

Well, what could?

Scale for one thing: whenever one tackles new technology on such a scale, we simply know that plenty can go wrong, and probably will, and what goes wrong worst generally will not be the parts that we had predicted.

And in this case, the sheer scale of any viable project of that type beggars the imagination of Joe Average and Percy Politician, and so does the variety of obstacles to overcome; if so much as the thought is to be worth while we must think in terms of delivering, not millions, but billions of tonnes, not annually, but pretty nearly daily.

Still, the times they are a-changin' and by now it is a matter of religious conviction that climate is a-changin' with them; and climate stable or climate unstable, human populations are growing and water resources are shrinking.

It no longer is too early to think once more of harvesting ocean water and ice. Few people realise how unstable climate really is, even without modern human culpability. Before our "industrial revolution" of the last three centuries or so, at least a dozen "civilisations", or at any rate established urban communities, were ruined or dispersed by droughts that lasted for decades or centuries.

Collapses of that type have happened on every major land mass where cities of any sort existed. The biblical seven lean years were altogether believable as a very mild instance. The very Sahara as we know it, ancient and dreadful as it seems to us, is a relatively young desert, largely having been savanna just a few thousand years ago. It was so recent a development that apparently a few immemorial Atlas cedars still survive where rare underground water sources happen to have sustained them.

Nowadays the idea of letting a large modern city die of thirst is practically inconceivable, so it is pretty certain that some drastic modern technological and infrastructural advance must be developed to supply the water they need, no matter how ridiculous such measures seemed in quite recent past. Certainly desalination with even greater sophistication and efficiency than what we can manage at the moment will be one of our necessary objectives. Just a few decades ago our current desalination technology would have seemed miraculous. Improved reticulation and redistribution of fresh water already is a must. Gathering and recycling fresh water from as yet unexploited sources will be vitally necessary. Greater efficiency in agricultural irrigation is long overdue, as agriculture in Israel has demonstrated dramatically.

Various possibilities often complement each other, for instance desalination works best when the input water is at most slightly impure, brackish, such as one might be able to gather from estuaries or from sea ice, rather than unacceptably saline. One way or another though, we need to explore and develop as many sources of sufficiently fresh water as we can, if only because different solutions are necessary for different purposes in different circumstances and different regions.

And we have the thirsty with us always.

Discussion of the potential technologies that I propose here were inspired by a drastic drought where I live in South Africa, though it is far too late for immediate application of this idea to that drought, and it probably is too early to take the ideas seriously at the time of writing. Anyway, we have had droughts before.

But never droughts that so threatened modern cities, and with every prospect of more and worse threats in future, anthropogenic global warming or no anthropogenic global warming.

And one must start somewhere.

How much fresh water would we need?

Think of a number…

We consume a lot of water already, domestic, industrial, and agricultural. No one knows just how much, but it definitely is beyond the untrained imagination; in fact I suspect that even the trained imagination manages only on the principle of "shut up and calculate". People in the know cannot afford to let themselves be distracted by the boggling of their minds in the face of realities. To begin now would be none too soon for rationality, though far too soon for the politicians and business powers that be.

A rough guesstimate at current global human consumption might be four teratonnes: four million million tonnes of fresh water — per year.

That alone is nearly as much as the entire flow of the Amazon River. It amounts to a few thousand cubic kilometres, and our rate of consumption is not decreasing; in fact many millions of people, from pole to equator, remain frantic for fresh water all their lives, and their demands for entitlement grow hoarser with anguish as the ages roll, and their desperation and rage grow similarly.

In our calculation or planning in this discussion we may ignore those desperate people; they cannot afford to do much about their situation, so a more practical beginning would be to provide a few billion extra tonnes of water per year for the typical large, affluent metropolitan region. A billion tonnes of water occupy about one cubic kilometre, just one large drop in the global bucket.

However even that drop is beyond the imagination of most people, and what is more important, the necessary scale of the engineering is far beyond the imagination of Jane or Joe Average, who seem to think that all you need to do to get all the water you want, is to install a tap.

Or, more likely, hope someone else will install it.

It would be funny if it were not so infuriatingly tragic: even more tragic than thirst.

Unless you happen to be really, urgently, thirsty.

Bulk water engineering and the design of new bulk water handling technology are not for amateurs; we already get water from many sources that Joe Average hardly dreams of. And if he did dream of it, he would be grateful to forget the dream on awakening. Most of us don't even realise that we get a lot of our water from underground, let alone from sewage — when there is enough sewage, which there generally is not. Not many people realise that many of our underground water sources are limited; using them amounts to mining of water that in many places has accumulated over thousands of years or many times longer, and replacing it with salt water.

Such supplies eventually peter out when the water mine is exhausted, or is ruined by damage to geological formations that hold it. Or it may get polluted, in which case it may be very, very hard to clean it.

Many people also don't realise that much underground water is unusably salty, often saltier than seawater, and that when rainwater percolates through to such salty groundwater, it commonly becomes unusably salty in turn.

So don't look to underground water for indefinite supplies, unless you happen to live in a blessed region where rainfall comfortably replenishes your clean water mine indefinitely and you can hope that it will continue to do so.

And dammed water, say from giant schemes like the Three Gorges dams, not only is in itself a limited resource at any given time, but is wanted for more than relieving drought; apart from producing potable water, it has to produce power and support transport. Such applications are not fully compatible; and they compete more and more severely as the water reserves run lower.

Not to mention that dams too, have ecological impacts, not all of them favourable.

So don't get too optimistic. We already have seen the mighty Colorado River reduced to a polluted trickle; the Nile is threatened by each of the many countries it passes through...

Watch this space; even the Amazon and Congo are not infinite...

Why the poles?

We must always remember with gratitude and admiration the first sailors
who steered their vessels through storms and mists,
and increased our knowledge of the lands of ice in the South.
Roald Amundsen

In the sea we have more water than we can use, though not more than we can pollute; and our planet-wide problem is not a shortage of water as water, but how to separate the water from the salt. The sun provides the planet's largest still, purifiers, and condensers, but only a fraction of the usable water goes to where we want it on land, in rivers, and in lakes. Even less ends up where we can use it for domestic and industrial purposes.

To add injury to insult, the condensed water often arrives in the form of floods, always wasteful, commonly harmful, and often deadly.

And most of what we do receive on land soon flows uselessly back into the ocean, where it once again is lost, carrying valuable soil and nutrients with it. And pollutants.

What drives that cycle is the fact that the sun heats the water, evaporating it. Sooner or later the vapour cools till it condenses or freezes. To use the water, we must intercept it at suitable stages between salt and salt. Not to mention other pollutants. Some of this interception is easy — waiting for rain for example, but by ignoring some of the more difficult options, we lose a great deal of water that otherwise could have been useful.

On this planet some of the largest and most dramatic regions of accumulation of fresh water are sub-polar. That is where warm air from temperate and tropical regions meets cold air, and dumps its water burden as ice in various forms. More importantly, sub-polar regions also are where seawater freezes.

As it freezes it more or less abruptly extrudes brine from between crystals of pure ice.

These regions are remote from where most people live and work, and in those regions ice in large masses is largely in unfriendly forms. Accordingly we have paid them little attention as sources of fresh water.

But that must change.

Just as we have been grubbing for oil in ever more incredibly difficult circumstances in recent decades, so we shall need to look at sourcing water from the more challenging, but more rewarding, less ecologically harmful, sources.

Almost amusingly, we can reflect that within remote living memory, before refrigerators were standard household appliances of the affluent, the seasonal harvesting of ice was a major industry in regions such as much of North America and parts of Europe; entrepreneurs would cut blocks from frozen lakes or the like. They would warehouse those blocks, and during summer they would transport the ice to major cities such as New York. For decades in such cities the iceman was as familiar a figure of the everyday infrastructure, as the milkman. Domestic ice boxes were designed to hold standard-sized blocks, and a suitably insulated block might keep food fresh for perhaps a week or more.

Extravagant people even made ice cream, producing the necessary sub-zero refrigeration by adding salt to crushed ice. The ice pick was such a standard household utensil that it figured in many murder mysteries. In real life even Leon Trotsky was reported murdered with one, though technically in his case it was an ice axe, and Trotsky himself never was reported to have insisted on the distinction.

Anyway, the sub-polar regions are textbook examples of where there is plenty of fresh ice at all seasons. It just happens to be regrettably inconvenient to collect and transport the permanent ice and convert it into usable form where it would be most welcome.

Oil and gold they say, are where you find them, and the places where you find ice in paying quantities, quantities large enough to slake the thirsts and cool the fevers of cities and nations, are places where you find cold.

For example in sub-polar regions.

Nor is that all; cold is not only where you can find ice, it is where you can make ice.

Surprise.

So what are you waiting for? Fetch!

But the question of what to do with your ice once you have found it or made it, leaves you with whole ranges of problems. As I shall point out, the fact that there might be problems does not prove that ice is not worth finding, but it certainly means that we cannot expect half-baked ideas to solve all those problems. We shall have to work hard to learn what to do with what we gain.

Some Practical Problems

The secret fountains to follow up, waters withdrawn to restore to the mouth,
And gather the floods as in a cup, and pour them again at a city's drouth
Rudyard Kipling, The Sons of Martha

Among all the practical problems we consider, we might as well start with the sheer scale of the need and the supply. Just moving the equivalent of a supertanker of fresh water is no joke. Let’s suppose it carries half a million tonnes — nothing special when one is carrying only water; convenient dimensions for a full load might be something like 420m long, 60m wide by 20m high. Nothing special, as I said: barely six stories high; you could hardly get four football fields on top of it and you could walk round it in less than 15 minutes.

Now, if you really think that is nothing special, try lifting or dragging a single cubic metre of ice. Try freezing or melting it. If you use a crane, see what it does if you drop the block or bash it accidentally. Tonne masses are big and unwieldy, but million-tonne masses of ice are unbelievably worse. Try standing by a twenty-metre ice cliff (which would be very modest; Antarctic ice shelves rise some 50m above the sea surface, and extend about 450 below). Then try to imagine how you should go about loading that into your tanker or dracone. (If you need to know about dracones, look up "dracone barge" on Wikipedia at https://en.wikipedia.org/wiki/Dracone_Barge .)

Simple to load? Just scoop out the ice with mechanised giant ice cream scoops?

Not really so simple.

Cold ice is quite a strong material, and the rate at which you would have to scoop it would be mind-numbing if you were to stop to think how much you would have to move to make it worth while; remember that to be worth collecting, water must be cheap and plentiful, and we need to think in terms of at least hundreds of thousands of tonnes per load, not single tonnes. Millions would be more like it. And even "warm" ice — ice that is almost warm enough to melt — is a lot harder than ice cream.

And ice cliffs tens of metres high are shockingly treacherous, especially when warm. You can't just park next to them with your bulk carrier and start loading; you and your ship could be kilometres under the sea, crushed, your bones being picked over by hagfish shortly after the first unexpected calving dumps a hundred thousand tonnes of ice on you.

And if you think that towing a cargo of realistic size is a doddle once you have it loaded on a barge or in a dracone, forget it. Ocean-going tug work is some of the toughest and most hazardous on the water. It also is expensive. And slow. For towing any mass of the order of a large cargo vessel the hawsers are huge and may be kilometres long, deliberately being dragged through the water to prevent disastrous consequences if one breaks, which even giant hawsers quite easily do if there is a sudden change in tension.

Well then, instead of towing, why not load up ice into your tanker and speed directly up to the customer city?

Also not as easy as it sounds. What do you do with your ice when you arrive? Unloading will need to be fast if you don't want to go bankrupt with your ship in port, and you will need to park your payload somewhere practical as you unload it. If you want to melt it, that will take huge energy, and even if it had melted en route you would need pumping machinery of huge capacity to deliver it to your reservoirs. And reservoirs cost money too. And not just any harbour can accommodate large bulk carriers.

Might as well give up. Just sit in the corner and cry about how unfair it all is.

Actually all these problems have solutions, some more promising than others. I shall discuss some of them, but all will need proper engineering and proper economic consideration before they deliver anything.

And they won't be cheap either. We will have to learn to live with water that doesn't grow in the pipes, water that costs money — more money than we have been used to paying.

Tote that Berg!

And one who licks his lips for thirst with fevered eyes shall face in fear
The palms that wave, the streams that burst, his last mirage, Caravan !
And one — the bird-voiced Singing-man — shall fall behind thee. Caravan !
And God shall meet him in the night, and he shall sing as best he can.
James Elroy Flecker Song of the East Gate Warden

The traditional scheme for farming ice, was to cut slabs out of surface-frozen lakes, and some of that still gets done, but it is not an approach of much interest to our topic. It has nothing to do with transporting water to places that need it in quantities that could quench the thirst of cities and agriculture. Its very objective is not the same; those people who used cut ice to sell, sold it as ice, not as water.

The needs they met were real needs, and they met them respectably, but they are not the needs that we are confronting here and now.

We really want to deal with sources that could in principle produce billions of tonnes annually, sustainably and without serious harm to the environment; preferably even helping to conserve the environment. And we might be more interested in water than ice as such. As a matter of fact, that distinction is open to consideration, as we shall see, but we must bear it in mind.

The earliest proposals for exploiting sea ice were to tow icebergs to places like Arabia. It was the obvious option, but hopelessly unpractical. Only small icebergs are towable, and they have inconvenient shapes and their behaviour under tow is very, very bad: they topple and yaw and split and all that. Also, they cannot be towed quickly, and not only do they melt continuously en route anyway, but moving them through the water really melts them quickly. To get some idea of how quickly, treat yourself to a soda containing a few sizable ice cubes. Select a well-behaved cube, push it under the surface with a drinking straw and gently suck up the liquid so that it must pass over the ice on the way into the straw. Within just a few seconds you will erode a hollow, and in less than a minute you can melt a hollow so deep that the cube can't slip away and you can drink freely. Pretty soon you can become adept enough to drill holes through more than one cube per glass of soda.

Now imagine what liquid seawater would do to any mass of ice passing through it day after day and week after week, such as would be necessary to deliver the ice for thousands of kilometres.

This is not my personal fancy, please note; people have experimented. The idea is a non-starter.

In summary, most regions in need of water, let alone in need of ice, are hopelessly too far from any realistic route to be served by towing icebergs.

But that was the good news. Even if you could arrive off Rabat or Beirut or Kuwait with your modest little million-tonne ice cube, a hundred metres high and wide, what now? Could you pipe it ashore before it all melted? Even if you could lift it out of the water and dump it on land, how would that get it into the water supply?Such practical problems are unending. Not that they aren't soluble in principle, but in practice many of them simply are not worth solving.

Especially because, as I explained, a million tonnes of water is just a sip; you would have to keep the sips coming pretty fast if the infrastructure is at all to be worth developing.

Let's think bigger…

Ocean-going tugboats are built for two purposes: to tow huge inanimate objects across the ocean at a snail's pace or to slam ahead at full speed into the teeth of a gale to come to the assistance of a vessel in distress. Of the two, it is hard to say which is the most exciting. Personally, I found the long slow trips towing a dry-dock, a dredger or even a whole factory in the shape of a tin-dredger, a more exacting experience than the salvage business. For, during the long trips, the officer of the watch develops a tendency to gaze astern instead of ahead, which he will find a difficult habit to lose. When, later, he is on watch on any other ship's bridge, pacing up and down at the comfortable walking speed that is the secret of relaxation, he will often experience a sinking feeling in the pit of his stomach on seeing the empty wake.
Jan de Hartog A Sailor's Life

The water from a billion-tonne iceberg would represent a significant addition to the water supply of even the largest city, but in every way would represent a challenge, both at the source and at the point of delivery...

Now, there are other approaches to towing icebergs, really large ones, in particular tabular bergs from the Antarctic, but all of them present problems of their own. The process would be difficult and so slow that precious little of the payload would get anywhere useful. It has been suggested that by sticking to cold currents such as the Benguela, that move from sub-polar to sub-tropical seas, we could improve the parameters.

True.

We certainly would be fools not to take advantage of such natural aids, but all the same, that is not nearly sufficient on its own. Even the coldest currents would not be cold enough to prevent ice from melting, especially when it is being towed through salt water, and as it approaches regions where the water is wanted, the air temperature would rise dramatically, causing faster melting above water level.

The natural lifespan of a large tabular berg in sub-polar water, if it has a mean diameter of some kilometres, is a few years. That is too short for towing even if towing were practical, and what is more, if we put everything we had into towing it, its lifespan generally would drop to less than a year. We would be putting all that effort into re-dissolving nearly all that lovely fresh water back into the sea instead of delivering it to a thirsty land.

Not attractive.

We could improve the balance sheet dramatically by coating the underside of the berg with sheets of plastic, using automated, remote control underwater craft, but the sheer scale of the effort would be sobering. For a comfortably sized chunk of floating shelf, say some ten kilometres across, we would need over 100 square kilometres of plastic material.

That is not in itself an unrealistic investment in material, but as an engineering feat it would be astounding. Designing the jacket to survive the trip long enough would be a serious challenge in itself; wave erosion and impact are shockingly powerful forces. Recovering the material afterwards, or ensuring that it would recycle harmlessly into the ocean in the form of innocuous fish food, would also be demanding.

Amylose film rather than non-biodegradable plastic jacketing might do the trick, but I am not sure that any realistic plastic jacketing would last well enough on the business leg of the trip. At present amylose certainly would be too costly, though one never knows...

Still, it does open tempting lines of thought. We might return...

...

And returning, I find that I forgot about Pykrete. (If that is an unfamiliar term, read the description at: https://en.wikipedia.org/wiki/Pykrete ). In short, Pykrete is a form of ice of increased structural strength and resistance to melting, imparted by incorporating small percentages of wood pulp or similar fibre. Pykrete can be created at sea by spraying doped water under freezing conditions. A freshwater iceberg, or a sufficiently large slab or cylinder of ice could be protected by Pycrete, though the technical problems of achieving even coverage might prove to be prohibitive.

Alternatively, fresh water ice, stored and handled as Pykrete, or jacketed with it, might be stronger, safer, and more durable to handle, sufficiently so to justify its use.

Please note that in this topic, I am strictly handwaving. I not only lack detailed proposals for the practicality of Pykrete projects, but even lack clear applications. But wherever, in sub-polar regions, one is thinking of coating objects with foreign materials such as plastic, it might be worth pausing to consider Pykrete as an option.

On melting at the point of use of the delivered ice, the fibre would be simple to filter out and recycle for preparation and retrieval of the next load.

What is so special about towing?

We need to quit arguing about whether the glass is half full or half empty — and instead
acknowledge that there's not quite enough water to go around.
Kate Brown

When you come down to it, the idea of towing icebergs is naïve. Towing them certainly does save all sorts of complications and ships, with no problems other than the loss of practically all your payload and the need for special facilities at the delivery end.

With problems like that, who needs droughts and disasters?

Well then, that doesn't sound encouraging, but do we have alternatives?

Yes.

To begin with, two forms of alternatives at least.

Firstly we could collect the water at the source (meaning mainly ice shelves in Antarctica, and glacier calving areas in the Arctic), and leave the floating bergs to the suckers.

Alternatively we could let a berg drift as it pleases, but begin by selecting masses suitably situated for currents and winds to deliver them efficiently; we then could proceed to parasitise them while they travel, benefiting from the distance that they drifted spontaneously. To do that we could accompany them with ships and equipment with which we could carve them up or speed up their melting.

What would that achieve?

To begin with, any payload that we could get on board a suitably designed ship or barge, no matter how slow and cheap that ship might be, we could move much faster and more efficiently than would be possible by towing the berg, and the ship could be far less dependent on wind or current. Once ice or water were loaded aboard, it could be delivered almost loss-free, without any specially urgent race against melting into the sea.

We also would need no more infrastructure at the discharge end than pumping and storage facilities. No magic iceberg-handling would be necessary. If the payload were conveyed by dracone, it wouldn't matter whether much of the ice had remained unmelted or not; the towing vessel simply could deliver the dracone as temporary storage along with the water it contained. After delivering the dracone, the ship could prepare for the next voyage and leave with empty dracones as soon as refuelling etc were complete, generally even before unloading the payload had begun.

In short, no towing of any iceberg would offer any attraction unless there were reason for positioning or rotating a berg. For example, a berg in a region of water too cold to encourage melting as required, might be towed, or at least nudged, towards warmer water, or if selective freezing were required, to colder.

What Sort of Vessel Suits Such Payloads?

We forget that the water cycle and the life cycle are one.
Jacques Yves Cousteau

Especially in the early days of gaining experience with polar water transport, we could experiment with second-hand tankers or tugs, but as experience accumulated, we might consider designing dedicated vessels for any of at least three options, all of them on a very large scale.

Buoyancy should not be a serious problem, because fresh water floats on seawater, and so does ice. Nor does fresh water in trivial quantities such as a few trillion tonnes pose any significant pollution risk even if spilt wholesale. So, laden or not, neither sinking nor pollution should pose any special risk.

Dracones, giant sausage-like balloons containing thousands to hundreds of thousands of tonnes of fresh water or ice, have certain attractions. The filled dracones could be connected in chains many kilometres long, and towed by tugs. This is no novelty; dracones have been used in similar ways for other types of cargo for many years, though on smaller scales. They have many advantages in flexibility and low overheads. This approach could solve the storage problem at the port of delivery, and also problems of necessary delays for melting residual ice so that it could be pumped ashore after docking; once delivered and secured, a dracone could be left behind for as long as desired, while the towing vessel immediately proceeded with its next task.

All the same, towing of any gigantic load of liquid in any form probably would be slower and more costly in energy than conveying the same load in a rigid vessel. It is not clear for example, whether large fluid-carrying dracones should contain internal baffles to control resonant internal sloshing, or whether they should have exterior contours or appendages to improve control and attitude in the water. Possibly some sort of resonantly contracting design of concertina-like dracone would be specially efficiently towable through water, but that remains to be demonstrated, and the dynamics almost certainly would be complex. The practicalities and economics would have to be assessed in each context.

There would be a need to shuttle empty dracones, and to design a dracone that is manageable both when very full and nearly empty might prove to be a non-trivial problem. Especially if it needs to be loadable either with mainly ice, or mainly water, or slurry. There are options for concertina designs or smooth, for example, and designs with various forms of symmetry. They have implications for working life, scale, streamlining, tendency to capsize or twist, or whether the difficulties with loading, unloading, dragging line astern or in bunches are acceptable.

Considerations of that type need not be insuperable, but nor can the design implications be dismissed as trivial.

The design of tankers for carrying massive cargoes of fresh water and ice should be simpler than the design of drogues, but they still open several lines of approach. They could differ from any previous designs of supertankers in several ways. Unlike the largest of oil supertankers, they would demand little precaution against pollution, because only the ship's fuel would be a serious hazard, not the cargo. A few million tonnes of fresh water spilt into the open sea would be a major monetary loss, but no more of an ecological disaster than a heavy rainstorm at sea. Accordingly, double-walled construction and similar precautions regarded as necessary for an oil tanker, need not be considered unless it were thought worth the extra expense and weight to reduce the risk of loss of the vessel.

Again, the size of the ship need not be limited by anything other than the available facilities at the designated ports of delivery and the hazards at the points of collection. In contrast to oil tankers, freshwater tankers or tanker barges, carrying volumes exceeding a million tonnes, could be routine. In fact they would have to be routine; we need water in vastly greater volumes than we use oil. And we use oil in staggering quantities. The very nature of the cargo and market would rapidly dictate new designs of vessels to accommodate water cargo, whether liquid or ice.

Any baffles, separated tanks, cargo containers, and leakage protection within ships designed for carrying water or ice would be matters of detailed design, rather than basic problems.

Whether they would be considered practical at all would be open to question, especially if their cargoes were mainly solid ice. Such vessels might be very efficient in transport and collection, but they might take months to unload, so they would be major liabilities in harbour.

Accordingly a third option would be comparatively attractive: giant barges. In essence they would amount to the equivalent of the tankers, except that they would largely be unpowered except possibly for manoeuvring, pumping, and crew accommodation. They variously might be manned or unmanned. Depending on their design they might or might not be connected in strings or in parallel for towing, and they might be used for storage as well as transport. If intended to store ice rather than water, they might be insulated, but independently of such considerations, they ideally should be very, very large, much like the powered tankers, only probably even larger. Maybe tens of millions of tonnes deadweight rather than hundreds of thousands of tonnes.

The advantages of each option would depend on the nature of the collection mechanism. For example, parking a quarter-million-tonne ship or barge anywhere near an iceberg or ice cliff, or even aggressive sea ice, might be suicidal. It might prove more practical to collect the ice or water with fleets of small foraging and loading vessels that capture it and process it before passing it on to the transport vessels.

Another factor is the cost of parking a vessel for months while it is being unloaded or waiting its turn to be unloaded. Proportionately, parking a special-function multi-million-tonne barge or drogue should demand a lot less overhead than parking a fully functional, smaller vessel.

Why ice?

People say that if you find water rising up to your ankle,
that's the time to do something about it,
not when it's around your neck.
Chinua Achebe

Ice has all sorts of disadvantages compared to water — harder to load, less dense, further to fetch, needing heat to make it usable, dangerous in large masses, melts inconveniently, can't be piped or pumped — the list goes on.

But some of those just can't be helped; if fresh water simply were available in any desired quantity wherever wanted we certainly would not consider prospecting for it in the form of far-off ice. As fresh water is increasingly at a premium however, or simply is unavailable in many places, we must go out of our way to get more, or we might as well stop moaning.

And from a different perspective some of the supply problems look more like opportunities.

Harder to load? Well, in some circumstances ice certainly is not easy to load; it is harder than efficient pumping of liquid water. All the same, as we shall discuss, suitable preparation and equipment can be developed for collecting sea ice, crushed ice, and slabs of ice. We still shall have to develop a lot of infrastructure and technology, but developing infrastructure and technology is necessary for exploiting any large-scale new opportunity.

And once properly loaded, ice can't slosh about and endanger the tanker; sloshing can be quite a problem with liquid cargoes. Sloshing is a deadly — and costly — problem with giant ore carriers for example, in which either slurries, or even powders, slosh about and capsize the vessel. It is not exactly an everyday problem, but not rare either; world-wide, as far as I can make out, there is roughly one such event annually.

Dangerous in large masses? Too true; ice certainly is terrifyingly dangerous, and dangerous in various ways too, but liquid water in large masses is no less terrifyingly dangerous — and dangerous in various ways too. Each needs its own techniques and precautions — there is no value to whingeing about it; buckle down and earn your winnings.

Less dense? Meaning that your ship can't hold so much? But that also means greater buoyancy, which means that the larger storage or transport ship or barge may cost no more to build than a ship designed to carry the same mass of water. And the stiffness of a mass of ice can be exploited to reinforce a suitably designed ship rather than decreasing its stability the way that sloshing liquid or slush would.

And the lower density means that it can burst pipes when it freezes? True, but that is more of a problem in buildings on land than ice freighters at sea. Routine problems like that are easily dealt with after the first few sinkings have taught us the first few lessons.

Further to fetch? How sad. But that only is true when nearby fresh liquid is available. Where none is available even distant ice can be worth fetching, and not especially distant either, in comparison to distant fresh water.

All these simply are realities to be approached intelligently and positively in context. That is what engineering is for.

Ice harvesting, limited supplies, and Carbon Dioxide

There is an old American saying 'He who lives in a glass house
should not try to kill two birds with one stone.'
Vladimir Nabokov Pnin

Mining or farming sub-polar ice, drift ice in particular, also offers vital advantages over exploiting seriously inadequate freshwater resources in temperate or torrid regions. The ice is plentiful and is continually renewed seasonally, whether we love the fact or loathe it, both in the Arctic and Antarctic, and it offers hopes of dealing with increasingly ominous threats of global warming.

For example, removing sea ice cover increases the rate at which cold air can produce ice, and accordingly also increases the production of surface brine that contributes to the natural cycle of cold water that conveys carbon dioxide to the depths.

Such capture of carbon dioxide is regarded as very, very important, fresh water or no fresh water. Whether the effect would be significant on a global scale is another matter, but it might very well remove more carbon dioxide than the operation produces. This would in particular be true if the major vessels involved were nuclear powered or hydrogen powered.

Or ice-powered, as I discuss later.

Now, eventually, ice harvesting might well become one of the planet's largest-scale industries. It might strip millions of square kilometres of sea-surface per year. As such it would be far more promising than some of the more harebrained schemes for carbon sequestration that enthusiasts popularly tout.

There is a positive feedback aspect to this concept: the greater the area of sea ice that gets removed, the more water gets frozen in winter, because surface ice insulates the surface from atmospheric freezing conditions, and removing the protective duvet of floating sea ice during winter, freezes water that otherwise would have remained unfrozen that year. Surface ice also prevents the solution of carbon dioxide in seawater, so, notionally, removing it could double the carbon sequestration in the harvested areas.

Some concern has been raised about the effect of carbon dioxide in acidifying the sea water and dissolving the shells of sea life, but I am inclined to discount that effect, because for one thing, the effect is gradual, and there would be strong selection, and even localised selection, for animals that could manage lower pH levels. In combination with that concern, there is no shortage of dissolved calcium and magnesium in sea water, so the sequestration would depend on no more than energy-consuming proton pumps in acid adapted organisms.

We do a good deal of that in our own stomachs.

And if disposal of more carbon dioxide in the sea becomes a problem, then the solution lies in reducing carbon dioxide output, not ice output.

Developing and maintaining a sense of perspective in system design is not an optional extra.

Another question is whether there is enough ice. Well, for convenience in meeting the purposes of this essay I am assuming that we might want to harvest ice to meet our total needs of fresh water. That is totally unrealistic, but the assumption is convenient for calculating notional feasibility.

We have two major sources of ice on any interesting scale: the Northern (Arctic) Ocean and the Southern (Antarctic) ocean. One might wish to neglect the Northern, because of its receding volume in recent years, and in fact I will ignore it for this essay. However, let us not permit ourselves to be stampeded into futility by facile assumptions. What matters is not how much ice there is, but how much its volume oscillates by season, and what happens to unharvested ice. As things stand we still have millions, if not billions, of tonnes of new ice forming on the Arctic circumpolar water every year, and as long as that remains true, the difference between winter and summer ice levels is roughly what we might reasonably harvest, because we know that it melts every year anyway. And the ice that melts seasonally is of little ecological value anyway, being too thin or too mushy for large animals to rely on it for support. So, properly harvested, even the Arctic seasonal freeze should be valuable, even adequate, for the needs of say, the pacific Northwest.

In passing, another source of fresh water that deserves attention, though it could not compete with sub-polar ice, is the fresh water that flows into the sea from major rivers, most notoriously from the Amazon, though the likes of the Congo, the Ganges, Orinoco, Niger, and Nile also could be exploited. Wherever such large outflows occur, the fresh water floats on the surface in such quantities that it is a lot more profitable to collect some of it than to waste it on sea fishes. Famously, ships in distress from lack of fresh water, out of sight of land, have been rescued by friendly advice to collect bucketfuls of water from the sea surface. The locals were aware that they were in the outflow of the Amazon.

Of course, we need not expect such water from all great rivers to be usable as is, but as I point out in another section, brack water is almost as valuable as fresh, when desalination is practical, or when it is possible to cultivate or breed salt-tolerant crops. If one can collect water containing say, 1% salt, which is hardly drinkable or usable, then by desalinating it till the residue is at the same concentration as the surrounding sea, one can shed the waste back into the sea without any pollution problems, and two thirds of the output will be pure, potable water. What is more, if it could be shed in suitable places, its content of soluble nutrients could support commercially valuable marine communities.

A more serious problem is that fresh ice is a lot more valuable than fresh water, but thirsty beggars make thirsty choosers. Brack water is better than no water.

The major source of ice for our purposes is from the Antarctic ocean. What the future holds we cannot say, but at present the seasonal range of coverage of sea ice averages from roughly 2 million square kilometres at minimum, to roughly 20 million at maximum. It would not be practical to harvest the entire area, but even if it were, and it were done early in the season, most of the surface would be frozen that same season, though hardly worth harvesting in less than a year or maybe three.

If (which is not plausible in the immediately foreseeable future) say 10 million square kilometres of sea ice could be recovered from the Antarctic ocean per year, that would be equivalent to rather more than the outflow of the Amazon, and more than human total freshwater requirements, without serious ecological penalties.

Now, I re-emphasise: these figures are not only rough, but quite artificial for the foreseeable future. All they are intended for is to illustrate that the scope for an adequate supply of fresh water will in principle suffice till long after most of the world's major rivers have suffered the fate of the Colorado river, not to mention the Nile and others in their turn.

And as I now shall point out: at an energetic profit.

Ice as fuel

Some say the world will end in fire,
Some say in ice.
From what I've tasted of desire,
I hold with those who favor fire.
But if it had to perish twice
I think I know enough of hate
To say that for destruction ice
Is also great
And would suffice.

Robert Frost

One major concern in all such harvesting and transport initiatives is energy. There is no room to argue against the value of ice delivered in usable form to places where it is wanted; but if we have to go thousands of kilometres to fetch it and spend months on the trips both ways, then the question of cost necessarily is very worrying.

Expensive water amounts to no water, except perhaps on a spacecraft.

And the most important cost in this connection is energy. It is not a cost we can dodge; arguably the most implacable constraints in our world are those of thermodynamics, paraphrased wryly as:

Do as we please to improve efficiency, we cannot do better than 100%.

We cannot achieve 100% except at a temperature of absolute zero.

We cannot reach absolute zero.

So one thing is certain: we can't get our water free of cost.

Well, we all know there is no such thing as a free lunch.

Still, that is not the issue. The question is how far we can reduce the cost, and whether the resultant profit would be attractive. We don't want fresh water to be an expensive luxury, but a profitable staple. If we can manage to make the cost of major dams look like economic and ecological suicide, that would be really gratifying.

So whether the proposals in this essay stand any chance of being practical, depends on how we can cost our options profitably.

And there turns out to be more to the equation than is obvious at first sight. We need to be alert, not only for the primary objective, but for subsidiary items that can make the difference between failure and a handsome success.

Meaning profit.

I suggest, not that we can beat the laws of thermodynamics, but that we need to examine their fine print more carefully, looking for options that we can exploit to achieve an actual, or extra, profit.

And one of them is that what matters in exploiting energy is not how much energy we have (there is plenty of energy all about us, more than we ever could use). What matters is the exergy, which depends not on the energy in the system, so much as the difference in energy levels between one part of the system and another.

Let us call the high energy level the heat source, and the low energy level the heat sink. For example, a flame at a temperature of say 1000 degrees in a chamber at a temperature of 200 degrees notionally performs no better as a source of power than a flame at 800 degrees in a chamber at zero degrees. The heat source in both cases is 800 degrees hotter than the heat sink. For more coherent detail consult the article at https://en.wikipedia.org/wiki/Exergy together with its links.

But here the important point is that one can improve the energy efficiency of a suitably designed system just as much by reducing the temperature of the sink, or at least preventing its temperature from rising, as by increasing the temperature of the source. In fact, by decreasing the temperature of the heat sink, one achieves somewhat greater efficiency than by raising the temperature of the source. For an explanation of that effect, consult the article at https://en.wikipedia.org/wiki/Carnot_cycle.

Now, for most of this essay we regard the problem of importing ice as implying a need to melt it at the reception installation. And that is reasonable; there is not much we can use the water for before it melts. And melting requires heat. And not only does it take huge amounts of fuel to drag it through megametres of ocean, but it also takes even more energy to melt billions of tonnes of ice.

And yet, a million tonnes of ice at a few degrees below freezing point, used constructively as a heat sink, offers the equivalent of something like 334 joules per gram, which works out at 334 billion kilojoules, ignoring the scope for a few billion extra kilojoules to bring it to typical ambient temperatures. Those 334 billion kilojoules are roughly equivalent to the energy output of 30000 tonnes of coal or similar fuel.

And no ash, no air pollution, no wasted fossil fuels or chemical feedstocks.

It also depends on the form in which we use that energy, but that is a question of engineering, not a matter for us to pursue here. I do mention elsewhere the value of exposing the ice to air, which condenses any water vapour, adding clean water to our yield from melting the ice, and at the same time produces large volumes of cold, clean air, which is valuable in various industrial applications, such as air conditioning.

If you do not believe me, ask them in parts of Canada (in Canada of all places!), where they recently had heat waves of over 50 degrees centigrade. They could have used a lot of cold air just then...

But those are details.

The important point remains, that we can extract more energy from the melting of the ice, than it takes to ship ice from the points of collection to the point of consumption. One almost is tempted to argue in favour of doing it all for the energy yield alone. Any water we then can extract at the point of consumption would be a mere bonus.

But one thing that does matter, is the influence of such factors on the engineering strategy. One strategy is to melt the ice and ship the water, but we thereby would reduce the profit in imported exergy by a factor of several hundred.

We have a strong incentive to import our water in the form of ice, in low-cost passive vessels such as barges or dracones that can be parked for months at the point of collection or delivery, with as little melting and as much freezing as possible until we desire to extract the water and apply the exergy to achieve desirable objectives.

A temperature difference of say twenty- to thirty degrees centigrade might not seem very exciting to a power engineer, given that each degree of difference offers only about four joules per gram, but the latent heat of melting of the ice amounts to nearly eighty times as much, so that a shipping a million tonnes of ice to a hot climate begins to make things look a lot more attractive than shipping huge quantities of fuel pole-wards to melt it, even if the power engineering challenges of exploiting such a small temperature gradient seem unattractive compared to the many hundreds of degrees available from flame or nuclear sources.

Remember too, that the way one uses energy makes a big difference.

Energy is energy, no matter what you do to it, but when one wants to increase the efficiency of a machine by increasing the exergy, the difference between the source and the sink, that can be more rewarding than using two sources of low-grade energy separately.

Or one could use the cold to produce cold dry air that would have taken a great deal of fuel to produce by refrigeration, but would take effectively no fuel when using warm, moist air to melt the ice. Then the fuel saved could be used instead to drive the vessels and equipment in collecting ice from the sea.

Ice types and harvesting strategies

If you don’t think too good, don’t think too much.
Yogi Berra

Not all sub-polar ice is the same. In this topic the main categories from our point of view are firstly drift ice, ranging from perhaps 10 cm thick up to say three hundred centimetres thick.

More particularly, we might be interested in pack ice, that is to say drift ice that covers a good three quarters of the local sea surface. Such sheets could be harvested more efficiently than chasing after individual flakes.

Secondly there are ice shelves and glacier calvings that float out to sea as they lose contact with land.

Thirdly there are the large, irregular icebergs typical of those in the Arctic; they too are from glaciers, but under circumstances different from those in the Antarctic.

Instead of mass ice, drift ice several years old could be precious, being easier to harvest.

Preferably we would look for sheets a metre or two thick, or fairly undistorted floes. Sheets of mature drift ice could in fact be so precious that prospecting for them by satellite should be rewarding as well as convenient and cheap. Such ice is fairly salt-free and could be collected by fleets of harvester vessels.

The design of the drift ice harvesters could be based on modifications of ice-breaker principles: unlike the traditional icebreaker, that breaks through floating ice by riding up on it till it falls through under its own weight, a harvester might invert the process by sliding beneath the crust and raising the ice in strips a few tens of metres wide and stacking them on board till the load reached capacity. It then could return the booty to the mother ship or the dispatching facility for loading into the barges or drogues.

While the load is being processed the harvester returns to its floe nibbling.

One cannot always expect ice to break neatly and obligingly according to our desires, so other, cheaper utility shuttle vessels could scavenge free-floating blocks small enough to fish out of the water, in lumps massing a few tonnes or tens of tonnes at a bite.

Because old ice is so much more valuable than young, it probably would be worth maintaining satellite surveillance of young ice fields as well as mature fields, until they were ripe and had thickened and shed their brine, rather than attack them while still salty.

Harvesting such well-formed sheets of ice should be relatively safe and profitable. A fairly small field, say a hundred kilometres square and with a mean thickness of about 1 metre, could yield about ten billion tonnes of relatively pure ice in manageable form. Of course, that would take some thousands of ships or barges to collect all the harvest and deliver it to the client countries and cities. The clients in turn would need facilities to handle the imports, but those need not be any more demanding than damming and treating the water of major rivers. It also would be a good deal less costly, especially if the water were collected and delivered in the form of ice that at local temperatures could be used as a power source.

Young sea ice, one or two years old, generally would be less valuable, because it is saltier, but it still is much less salty than seawater. So where there is no conveniently pure ice, it still could be worth harvesting young ice.

There always is scope for more design, so I do not go into detail here and now, but for example, polar storms at sea can be very severe, so it might turn out to be worth designing some of the ice harvesting and management craft as submarines, preferably nuclear submarines. Whether they did most of their work on the surface or not, they could ride out the worst storms in deep water, when submerged a few tens of metres.

The big lumps

A sea setting us upon the ice has brought us close to danger.
Henry Hudson

Calving glaciers and irregular icebergs might well prove too dangerous to be worth harvesting, but their substance is tempting, being large masses of practically pure water. Practically all the major bergs originate on land, from snow and other precipitation, so they don't contain forbidding amounts of brine. Even those that originate from collisions of exceptional masses of drift ice generally are old enough to have lost most of their brine.

So if we could find efficient and effective ways of cleaving them into harvestable slabs, that should be rewarding. I have no firm suggestions as yet, but explosives or injection of compressed gases or seawater might be used to smash bulk ice into harvestable sizes or to induce calving. ANFO probably would be the cheapest and safest explosive, but liquid oxygen or hydrogen peroxide mixed with fuels such as propane or hydrogen might have advantages of speed and cleanness. One would not want to use highly brisant explosives, because it would be more efficient to load large slabs of ice than crushed fragments, and would entail less salt pollution.

Instead of drilling into mass ice, we might find that light artillery specially designed for shooting charges into dangerous ice masses, might work rapidly and efficiently enough to be valuable. After all, they would never need to work at ranges of more than a couple of hundred metres. The propellant could be a gas/air system such as propane. A suitable gun based on such a principle would not need any propellant cartridge; Diesel-type compression could render ignition unnecessary.

Ice shelves attached to land might best be avoided for reasons of safety and possibly ecological considerations, but detached or detaching floating shelves of pure drift ice that simply would melt uselessly as they floated towards the equator, should be worth intercepting in time for harvesting. A fairly realistic tabular iceberg with a harvestable thickness of 100 metres and an area of 250000 square metres (say 5 km square) should yield about 25 million tonnes of fresh water. How to harvest it is a more complicated matter, because one cannot simply skim it like cream or like sea ice.

Really large floating ice shelves, such as those of the order of 10 billion square metres would be very valuable in principle, but it hardly seems possible to harvest more than a fraction of such a shelf before it broke up. All in all, sea ice seems to be the most promising large scale routine resource, but though northern hemisphere icebergs might be hard to handle, Antarctic floating shelves, whether free or still attached to land, do suggest special value. It should be possible to develop special quarrying techniques to blast vertical slabs from the sea faces of such shelves. Slabs of 1000 to 100000 tonnes, roughly one to ten metres thick, could come to float safely, flat and shallow in the water, after being cleaved off the seaward face of a shelf. They then could be loaded directly into suitable craft, if necessary after further cleaving to fit the equipment. It might not be as safe or easy as handling dominoes, but then nothing is as easy as it looks, especially not as easy as it looks to the amateur watching a professional at work.

But 1000-tonne floating chunks of ice in cold water should be attractively profitable items for quick loading onto a million-tonne deadweight barge, leaving room to be filled in with crushed ice or skimmed fragments.

So in general, it might be possible to harvest enough shelf ice to be worth while, especially in very high latitudes, where freezing winter cold alternates with summer temperatures above freezing. As we shall see, cleaving and quarrying are not the only options; such alternation could be exploited in various ways.

As already noted, explosive nibbling designed to detach harvestable chunks in huge quantities should be practical. It might be particularly valuable where warm ice is weak and starting to melt faster in warmer water.

It might even be worth exploring options for tethering major ice shelves that threaten to separate and drift wastefully away. Nowadays we usually have several years of warning of the separation of huge shelves. If we could slow down their separation enough to match the maximal rate of nibbling at the seaward margin and melting from beneath, that would pay for quite costly tethering.

But, tethered or free, where the shelf still is cold enough, thick enough, and stable enough, it might be worth installing our equivalent of ice-cream scoops, though the resemblance to your familiar retail ice cream scoops would be remote. Devices like the leviathans used in open cast mining of coal could strip huge areas of ice onto transport facilities for loading onto barges or into dracones. As the upper surface was stripped from a shelf of say, 100 to 500 metres thick, the ice sheet would float progressively higher till the shelf in the mined region became too thin for stability. Then the equipment could up sticks and move on to thicker ice, leaving the residue for collection along with ordinary sea ice. The final residual layer could be broken up into suitably sized blocks for direct loading – after retrieving the valuable equipment for the next sheet of course.

It is not clear that this strip-mining approach would compete successfully with collection of thin drift ice or nibbling at the edges of shelves with explosives, especially in the early years of the industry, but exploration of the options we may leave for future generations.

The fact that ice shelves are melting from beneath and from above suggests other approaches. In the warmer sub-polar regions in summer, suitable pigments on ice shelves could collect sunlight to create ice lakes kilometres across and many metres deep, well worth pumping directly into barges and dracones. No ice breaking involved. Just spray your pigments, such as carbon or dark clay or soluble dyes and wait till next season to start pumping.

Irregular bergs probably could not be scooped easily enough to justify the installation of equipment in the same way as big shelves, but they might well reward explosive carving or smashing into blocks for loading, as I already have described. Similarly, the edges of tabular bergs could be cleaved vertically or nibbled into loadable blocks. For example, if submarine craft became established for sub-polar ice prospecting, it should be fairly practical in deep water to cleave floating bergs without explosives, using drilling from below plus hydraulic pressure to force calving.

The fact that fresh water floats on salt has other promising implications. Barriers of biodegradable polymer foam could be extruded by robot underwater craft, forming fences beneath ice shelves in suitably chosen locations where the water is still and there is little relative current causing water exchange. The barriers' buoyancy could hold them against the underwater ice ceiling. Any molten fresh water would remain against the underside of the shelf by its buoyancy. Alternatively, the craft could carve hollows beneath the ceiling by directing seawater jets upwards. In either case, holes drilled from above down to the underwater domes could enable freshwater melt to float upwards for collection.

Because of contact with the seawater, much of such molten ice would be brack, but as noted elsewhere in this article, even brack water is valuable. Depending on which options would be most profitable, it either could be delivered to market directly, or pumped into ponds on the shelf surface to freeze into plates of usable purified ice in winter.

Deliver ice or water?

Diarrhea, 90 percent of which is caused by food and water
contaminated by excrement, kills a child every fifteen seconds.
That's more than AIDS, malaria, or measles, combined.
Human feces are an impressive weapon of mass destruction.
Rose George

Delivery of either ice or water has its attractions and each presents its own problems. Water is easy to pump aboard in loading the harvest, and to pump ashore in delivering the water. Water also is compact, either in itself or if we use it to fill the gaps between ice blocks in storage vessels' holds. But it also needs special precautions to handle at sea and it cannot be stacked like solid ice blocks. Also, its capacity for storing cold is small, compared to the latent heat of melting of ice. In industry concentrated cold can be just as valuable as concentrated heat. That is why we who remain ashore spend money on freezers, heat pumps, air conditioning and the like.

Accordingly, as described, massive ice delivered to warm regions where suitable infrastructure is established, could be valuable, for instance in cooling and drying air, and in the process it could collect a fair amount of condensed water from the warm, humid incoming air. The cold also could be used in heat pumps to freeze seawater or brack water to produce ice from which to collect pure water.

Again, at the delivery end, seawater warmed by solar power or heat pumps could be used to humidify air taken in to melt the ice, or to or carve mass ice while yielding an extra profit in desalinated water. Air that had been cooled and dried in such ways could be used for air conditioning, much as one can use waste heat from power stations for combined heat-and-power schemes.

Ice delivered in such masses rather than in loadable blocks would be difficult to get off large ships and therefore would be something of a liability if it took months to unload. This would be a good reason for using low-value dracones or barges for transport. Such ice-laden vessels would serve as storage buffers while the load thawed and got pumped ashore as required.

Meanwhile the tugs could have returned polewards, taking previously emptied vessels with them. Possibly they might have fetched a few more full loads on successive journeys by the time their previous load had been consumed.

Brackish ice might be expected to produce more saline water from its lower levels as it melted, the upper levels being effectively pure water, while the brack material could be desalinated and the brine dumped. Some brine would remain after desalination of brackish water until it became too concentrated to be worth further desalination. In contrast to the residue from desalination of seawater, the volume of brine from brackish water might be too small to be worth attention, so there would be advantages to desalinating it to no higher concentrations than the local seawater could accept without special treatment. As mentioned before, such salt water is likely to contain nutrients that would favour the growth of valuable organisms, including photosynthetic life forms that consume atmospheric carbon dioxide.

For one thing, such conservative desalination would remove the problem of disposal, because the brine then could be dumped anywhere into the sea without special precautions. The problem of disposing of brine after desalination to concentrations greater than that of local seawater has turned out to be a serious concern in practice.

The technology of managing such processes economically could become quite sophisticated.

Why icebergs at all?

We buy a bottle of water in the city, where clean water comes out in its taps.
You know, back in 1965, if someone said to the average person, 'You know
in thirty years you are going to buy water in plastic bottles and pay more for
that water than for gasoline?' Everybody would look at you like you're
completely out of your mind.
Paul Watson

Icebergs, especially large tabular icebergs, are very concentrated sources of water, and in suitable circumstances are less seasonal than drift ice. They also tend to be very low in salinity. This suggests that it should take less energy to collect them than it would take harvester craft to retrieve drift ice.

It also might be easier and cheaper to deliver potable water from icebergs than from thawed young drift ice that might be expected to be more saline. Accordingly it might be worth breaking large bergs into manageable blocks with explosives, as already suggested, after which the blocks could be loaded or broken up mechanically into loadable sizes.

Why not make ice instead of collecting it?

The society which scorns excellence in plumbing as a humble activity and tolerates
shoddiness in philosophy because it is an exalted activity will have neither good
plumbing nor good philosophy: neither its pipes nor its theories will hold water.
John W. Gardner

The primary objective is to deliver water to the thirsty clients, and for them to receive it exactly when required and pump it to where it is required is the obvious option. However, the entire operation is costly in energy, infrastructure, and human resources; the source is largely seasonal, and to consider every material saving and gain is in the enlightened interest of all parties.

Polar ice is in many ways valuable, but Nature does not present it on a tray, ready for consumption. The most plentiful and accessible forms of drift ice tend to contain more salt than we would like, though not nearly as much as seawater does. Even if we cannot get pure water, sufficient reduction in salt content is of value; we might well ship brackish water to willing clients who could process it further according to their needs. That at least would be cheaper than desalinating seawater, especially on a huge scale. In short, where local circumstances are suitable, we might have better uses for large quantities of brackish water than dumping it at sea.

Again, brack water, say 0.1% to 1% salt, compared to seawater's 3% to 4% or so, also could be processed at the site of collection in subpolar regions, by freezing in polar winter instead of shipping it to be desalinated on delivery; that could work better than freezing seawater, and produce ice much less salty than frozen seawater. To begin with, seawater is rarely still, so a lot of things that seem simple to the landsman, become terribly complicated in real life at sea. For instance, the turbulence causes mixing of surface waters, and mixing makes it difficult to discard the salt. So finding ways to keep water still can be very valuable.

For example, imagine a giant tabular ice sheet near Antarctica, either still landfast, moored, or not yet about to fragment or proceed rapidly north. Imagine that we had excavated a large, deep quarry into it, probably by solar melting, pumping out the fresh water to our tankers for freezing during the following winter before shipping it to the client ports.

During summer we could dump our marginal harvest of brack water into that hollow, where it would melt high quality, low salinity ice, increasing the volume of brack water while decreasing its salinity. The hollow might be excavated by adding traces of carbon black or organic pigments such as chlorophyll or other porphyrins to promote solar-powered melting. The surface of the water in the hollow would be relatively still compared to the turbulence of the sea. Because of its stillness and low salt content it would freeze more easily than sea water and would form sheets of ice rather than porous mats of crystals. During the sub-polar winter such water should freeze thick, say 30 cm to 1 metre or so, and the ice in such a situation should be of high purity and undiluted by seawater: Nature's free desalination service — or nearly free anyway. Come the harvest season in spring, or even during the polar night if that proves practical, such effectively pure ice on a stable surface could be collected and loaded onto transport craft. The process could be promoted by spraying the fresh or slightly brack water into the cold air, collecting the solids directly into the transport vessels with most of the desirable freezing already accomplished.

Such preprocessing should at least be easier than collecting clean ice from a restless sea surface. For one thing, to freeze seawater on open sea is neither as fast nor as easy as it sounds, because water that contains about as much salt as seawater does, does not expand as much as fresh water does when it approaches its freezing point, so it does not float as well, and it takes longer to freeze over deep water; and it tends to sink a few times before it freezes.

Once the ice harvesting industry had matured, there should be large numbers of dracones or barges continually available, but not yet fully loaded. Or, if loaded, their water might be brack. Such craft could be left with their holds open for the winter or the shedding of their heat content into the cold atmosphere could be accelerated by spraying, stirring or other dynamic exposure. The diluted saltwater, very likely nucleated with fresh ice, would freeze from the surface down. The deeper layers would concentrate the salinity while their upper layers would improve in quality. Come springtime each vessel could be assessed, either discarding the brine, preparing it for appropriate further treatment, or using it to freeze fresh water.

Meanwhile the harvesters could fill up the vacated ice quarry with good water pooled from other sources. Each craft would be dispatched to the home port when it filled.

If ice harvesting vessels could chase sufficiently cold weather and sufficiently cold seas, freezing could be induced by pumping seawater over cold surfaces that prevent convection over deep water. The ice could be sieved off, leaving the brine to go overboard. Such ice would contain salt, but probably less salt than 1-year-old sea ice, and collecting it would require no assistance from ice-breakers. The product could join the brackwater-processing stream.

Possibly, in water covered with enough ice to suppress troublesome swell action, large belts of suitably textured plastic netting could be drawn over the sea surface at a rate controlled to bring in a coat of freezing ice that gets shed into the hold as it passes over. The belt then passes below the incoming mat to freeze again on the way back in.

Or it might be better to design ice-making craft equipped with large areas on board, onto which water is pumped to freeze, the ice being skimmed off as the brine returns to the sea; it is futile to discuss details when the implementation still is so far from practical design.

When conditions are favourable it could be better to utilise ambient cold to process and reprocess brack water or liquid fresh water on board instead of shipping brack water to the client ports. The more usably pure ice that can be delivered ready for final processing on land, the greater the profit.

One of the problems with using young sea ice is that freezing seawater collects in fluffy or spongy mats of crystals, and such mats contain a lot of brine. Possibly crushing such ice would usefully reduce its brine content, but I have no idea how practical that would be. However, the complications of handling briny ice sponge could be circumvented by providing suitable surfaces to nucleate the formation of compact freshwater ice ready for harvesting. Such surfaces could be provided by heat pipes cooling the seawater by shedding its latent heat of freezing into the subpolar winter air. If the pipes were covered in silicone or suitable plastics, the resulting solid ice could easily be harvested.

Alternatively, freshwater ice itself should be perfect for nucleation; relatively small amounts of fresh water could be sprayed over sea just approaching the stage of freezing, and the fresh water would freeze solidly, not like blotting paper full of brine. Or snow harvested from the polar surface could be used for the purpose. Or coarsely crushed brack ice could be scattered over the water surface for similar nucleation. Then the relatively clean new ice could be harvested more cheaply and profitably than by processing it at the point of delivery.

In effect, subpolar conditions could be used in various ways to accomplish direct desalination by freezing. Desalination by freezing was attempted in the mid-twentieth century, but it never was energetically profitable -- however, it might become profitable in subpolar winter conditions on scales of millions of tonnes.

Ironically, if we were to import ice to thirsty countries, the value of ice as a heat sink might resurrect desalination of sea water as a viable technology. We might not get two-for-the-price-of-one, but one-and-a-half for the price of one still can be an attractive prospect. And ice or cold water can yield a bit extra by condensing humidity from the air, as I mention elsewhere.

It all is very speculative, but that reflects the scale and the variety of the potential, rather than the unpracticality of the suggestions. The field will reward the engineers who develop it, not the scoffers who rage at their own inability to conceive the opportunities.

Chill as fuel

Don't find fault, find a remedy; anybody can complain.
Henry Ford

It seems likely that, given winter temperatures of well below -20C near the Antarctic coast, it should be practical to exploit that cold as a source of power. We already have contemplated using the cold air to produce ice in various roles, but really, that seems to be a narrow view of important opportunities.

Understand that, though the ambient temperatures near the Antarctic coast are not nearly low enough to liquefy gases such as O₂, N₂, or even CO_2, they are low enough to reduce the costs of producing, storing, and working with, such gases. Furthermore, Antarctica is a source of significant renewable solar and wind power — wind at all seasons, and solar photovoltaic power for nearly half the year, including a lot of midnight sun during high summer. If it were to support a large industry of clean power accumulation, that resource could be enormously valuable once the scale of operation grew large enough, and we could exploit it without importing expensive, polluting, non-renewable fossil fuels.

Various renewable power units could be used at all seasons for accumulating compressed gases and possibly even for separating some of them. In particular, they could be used for condensing CO₂ as a liquid under pressure at winter temperatures, and for cooling air or even O₂, and N₂ if desired, for storage either as gases under pressure or as liquids in cryogenic storage.

"What on Earth for?" I hear the engineers cry! Understandably, because there is not much market for such products so far down south, and though compressed gases are valuable in industrial countries, it would be out of the question to produce them for commercial export thousands of kilometres to the north.

Yes, but compressed or condensed gas can be used for driving engines. In fact it is rather a good medium for storing power for such functions. And it is a very good medium for storing cold, because one need not store one's cold at such low temperatures; extremely low temperatures are harder to maintain than moderately low temperatures — and as the comfortably cold gas expands and the pressure drops, it cools accordingly. The thermodynamics present tempting opportunities for sophisticated designers.

The following proposals are not to be taken seriously for early phases of development, but within a few decades of experience and expansion, they could become downright attractive, both commercially and ecologically. As an analogous example, not too many years ago, wind and solar power did not look at all promising, but already both are goring many of the sacred cows of the traditional power industries.

Such cold could be welcome as an aid to stripping greenhouse gases such as CO₂ and H₂O from the atmosphere directly, either for industrial use as a by-product, or simply for disposal wherever it might be suitable. That objective is not of direct interest to this project, but collecting CO₂ might render subpolar freshwater extraction industry carbon-neutral or better.

More directly, condensed or compressed atmospheric gases could be used on site or loaded onto transport vessels as fuel to be consumed at warmer latitudes. O₂or oxygen-enriched air might be used in combustion engines as a means of supercharging, but I prefer the idea of using the gases as they are, to drive the ships' turbines without using fossil fuels. For that we do not want the gases to be cold; in fact it would be good to heat them up, and the hotter the better. Reducing the pressure on the gases as they are used for propulsion could require the harvesting of heat from the environment; delivery pipes exposed to the air, or even to sea water at temperatures above freezing, could create ice or condense water to add to the payload on the way home. In doing so, the waste heat would warm the gas to drive the vessel.

In this discussion it would be premature to propose details of how to manage the thermodynamics of allocating energies and materials most profitably; for one thing, such processes would only be worth while on a very large scale, after a lot of smaller-scale development had matured. But the scope for establishing a clean industry of global importance should not be ignored. Again, we should reflect on the explosive growth of the wind and solar power technology and industry in recent years, when just a few decades ago they looked derisory.

Why not pipe ice instead of shipping it?

I love the sounds and the power of pounding water,
whether it is the waves or a waterfall.
Mike May

This obviously sounds unattractive for clients near the equator, and there is no question of anything of the kind in the short term, but the need for fresh water world-wide, shows no prospect of easing. Meanwhile the population is increasing. There certainly will be an increasing need for global water reticulation. The necessary infrastructure will be far too huge to pop into existence suddenly. One of the early forms will very likely be large, long-distance ducts for shipping ice and slurry from the sub-polar regions to consumer regions.

Transoceanic ducts could be collapsible modular submarine pipelines of suitable tough plastic, each say a few kilometres long, with control and communication modules at one end or both, designed to control their buoyancy at each unit’s appropriate depth. They could very likely be used for communications and power transmission too, and maybe for certain types of material transport as well, very likely containerised.

The water ducts could be say a few metres in internal diameter, at least partly driven by wave power. Modules would serve simultaneously as ducts, processing units, and buffer storage. A duct unit with an internal cross sectional area of ten square metres and a length of one kilometre, would have a capacity of 10000 tonnes of water. A 1000 km pipeline could act as a buffer store for holding ten million tonnes. Not huge, but enough to matter.

If a portion of the capacity were reserved for air to be fed into the warm end, it could be used partly as a source of water of condensation, and partly to melt or at least warm ice at the cold end. Where it is released at the cold end its excess pressure could be used as a source of power. For instance it could contribute to ice breaking and loading.

Brack, schmack!

Seeing that our thirst was increasing and the water was killing us, while
the storm did not abate, we agreed to trust to God, Our Lord, and rather
risk the perils of the sea than wait there for certain death from thirst.
Alvar N. C. de Vaca

As already mentioned, one thing we cannot expect is to get pure water from sea ice. Old sea ice generally has shed most of its brine, and ice shelf and glacier ice are largely old snow deposits, so such classes of ice generally have very low salinity, but in practice we must expect pollution from contact with seawater; for example shelf ice may soak up a lot of seawater because it is porous, and some of our most easily harvested ice will be just a year or two old — it still contains too much brine anyway. To shed much of that brine would take another year or two of warming and cooling by the seasons and of massaging by storms and swells.And such delays are unwelcome to industrial engineers.

Some old ice might be drinkable when melted, but not really up to standard for heavy irrigation and commercial potability. Really young sea ice is barely drinkable in times of desperation if at all: it might contain say 1% or so of salt. Seawater usually is somewhere between 3% and 4% salt, and realistic desalination is practical for salt solutions of up to roughly twice that concentration.

However, the cheapest, fastest, and most sustainable desalination is the purification of large volumes of slightly brack or otherwise impure water. It certainly is better and cheaper than trying to desalinate seawater.

Firstly, one does not simply chuck weak brine into the machine and get out pure water plus concentrated brine. Different strengths of brine require different treatments with different membranes and pressures and energy consumption, and ecologically acceptable disposal of concentrated brines is more difficult than disposal of weak brine.

Accordingly, if one cannot provide the client with pure water, he might well be willing to pay for say 0.3% brine, about ten times weaker than seawater, so that he only discards about 10% of the output at 3% concentration instead of discarding 50% of the input brack water. He can do so without precautions against pollution, because at that rate the discarded brine is pretty close to the concentration of raw seawater. For most commercial purposes a solution about fifty to one hundred times weaker than seawater is usable as is, with no more discarded output than from processing most kinds of fresh water.

Mind you, do not take these figures too seriously; the intention is mo more than to give some idea of the major principles. In practice desalination is not as simple as it sounds; cleaning, backwashing and so on make for some waste as well.

Again, where sea water is used for industrial cooling, such as for power stations, the waste heat, which is what the water is used to carry away, could be manipulated, using heat pumps or similar tricks, to evaporate as much of the brine as practical, and that evaporation incidentally is the most effective consumer of the waste heat, and the vapour could be condensed into water pure enough for immediate use.

"Well then, why has that never been done?" I hear you cry?

That is not as simple as it sounds; it already might be standard in some applications for all I know, but certainly at the time of writing it is not common practice, and not long ago it would have been regarded as ridiculous; even now it would require special justification and special circumstances to be practically profitable, but the same could have been said of solar power or wind power, just a very few decades ago.

As for how to apply the heat from the condensation of the water; it could be especially valuable for melting deliveries of polar ice, as I already have mentioned.

Whether harvesting high-value chemicals from desalination or ice harvesting waste could be worth while, is a point for chemical engineers to consider. I suspect that there is room for such projects, but I am not able to develop the idea any further at this point.

The upshot in any case is that ice harvesters need not insist on pure-water ice, but would need to assess every major item they attacked or brought on board. They would not mix relatively strong brines with more or less potable water, and they would price the water according to its intended purpose and the amount and nature of purification or dilution it would need. No doubt such things as dates of delivery, contracts, and special circumstances would affect prices too.

Future markets in water promise to be a very interesting field of study and practice.

Ecological impacts of ice harvesting

When elephants fight, it is the grass that suffers
Attributed to an African proverb

Everything anyone can choose to do, including avoiding doing anything at all, entails consequences. If it did not, it would be pointless doing it — including doing nothing. As a rule, the larger the scale and relevance of the action or inaction, the greater the consequences.

Ecology in particular is affected by almost any change on a large scale, including the growing effect of a static condition or trend, and there is a tendency to regard every such change as pernicious. Such disapproval commonly is justified, but often the outcome is no worse than reasonable alternative actions would be in the long term.

Consider for example the stripping of ice cover from large areas of sub-polar seas. It sounds like vandalism, but suppose that as an alternative to stripping, I were to propose covering a million square km of sea surface with ice ranging in thickness from 10 cm to 40000 cm, with all the associated implications for heat exchange, gas exchange, ionic migration and exclusion, exclusion of light, and exclusion of large classes of both animals and plants. That would be at least as harmful as stripping. Right?

And yet, that would be the precise equivalent of leaving the current sea ice unharvested, without human intervention, on a scale beyond anything proposed in this essay, and without any clear improvement to human, plant, animal, or climatic situations. And in nature the cycle continues practically annually throughout major regions, global warming or no global warming.

Furthermore, if ice collection were to become established as an industry, then harvesting, especially in the early days, would largely be confined to free sea ice, whether continuous or fragmented, simply because it is safer, faster, and easier to collect than floe ice or iceberg ice. In fact, it is not yet clear to what extent ice that could most profitably be collected would be free-floating pancakes or fragments of ice sheets broken by wave action.

In the natural course of events huge areas of sea ice melt annually in summer and reform to a thickness of about 10 cm to 1 metre each winter, largely in the Antarctic. To harvest such ice towards the start of the melting season could seldom be harmful at all. In fact, there is at the time of writing, growing alarm at the rate of fresh water entering the Southern Ocean from melting ice, especially from the glaciers.

Fresh water floats on the surface instead of sinking, so such a floating layer will prevent the turnover of surface water to the depths. In contrast, cold and salty surface water is dense, and inclined to sink, especially when stirred by wind. It then carries soluble gases down to the depths, and the most important soluble gases in that region are oxygen and carbon dioxide.

We want to send down plenty of oxygen, because the marine life in the depths needs it. The last thing we want is to create a dead zone down there; it would be a disaster beyond calculation; certainly of planetary proportions.

We also want to send down as much carbon dioxide as we can; the deep sea is one of our most important carbon sinks.

So the more fresh water we can strip from the southern ocean surface in the form of ice, and the colder we can leave the salt water by exposing it to the winter air when the ice is gone, the better for our planet.

Two forms of free-floating drift ice and pack ice could be worth harvesting: three years old or more; and young ice, less than three years old, sometimes only months old. Areas of either type might be large enough for harvesting in a given region and season.

Unfortunately, young ice tends to be unattractively salty, but as I point out elsewhere, even brack water is valuable because it can be desalinated more cheaply than water from the open sea, and the waste brine, if not to be used for other purposes, can be limited to harmless salt concentrations that may be dumped safely.

The implication is that profitable harvesting need not be limited to effectively salt-free ice. For example, if a product of 0.1% salt is acceptable, and the brack water salt content is 1% , then about 70% of the brack water could be extracted, harmlessly discarding less than 30% of the input at the concentration of sea water. If the input brack water contained 0.35% salt, the yield would be more like 90%, and the desalination would be easier, faster, and cheaper than desalination of sea water.

Initial desalination might be done at the site of delivery, or various techniques could permit most of the processing to be done at the site of collection to produce low-salt ice instead of shipping briny ice immediately on collection. Shipping water instead of ice would generally be less desirable; I discuss several considerations elsewhere in this essay.

The details of the state of the input ice would depend very much on the ice sources locally available. Sea ice quality varies according to the region and the conditions under which the ice forms. Old icebergs tend to be very pure ice, while young drift ice that formed from grease ice, shuga, and frazil (fine crystals of ice growing on cold seawater) may contain more like 1% salt. The sheer variety of ice forms and their names is too great to deal with in this essay.

There is plenty of discussion of the topic online, for example in various Wikis. Whether it would be practical to begin the processing of brine-rich ice by squeezing it during collection, I do not know, but such options could be worth study in regions where young ice is the major harvest.

Anyway, in regions where ice would have melted annually, it would be beneficial to remove it strip-wise before melting begins. Such harvesting would have little ecological effect in any but very shallow water. On the other hand, if we removed ice at the height of the freezing season, the surface would be covered again within days, and that would be too fast for most organisms to be much affected, whether they were plant or animal, such as krill in the process of propagation. After stripping ice from freezing waters would be a good time to spray traces of soluble nutrients such as iron and zinc onto the open sea surface. Quite a slight concentration below the newly formed ice should dramatically increase the harvest of the algae that feed the krill when the sunlight returns.

New annual ice would be left for most of the season, whereas harvesting more valuable older sea ice would be delayed for say, 3 years at least after each harvest.

Studies should demonstrate whether it would be worth confining harvesting to local strips, in deep water, so that no organisms, whether algae or crustacea, are far separated from intact surface ice, and so that there are no significant coherent effects on the sea bed and its communities: no brinicles for example. I doubt that strip harvesting would be worth it, because the ice should cover the surface again within days or weeks, especially in the cold seasons. But either way, it could be a realistic option. Where harvesting has created strips of open water or thin ice, it might for example save the lives of many a marine mammal or diving bird.

One might wonder about my being so optimistic about the recovery of surface ice after harvesting, in the face of Arctic ice recession, but to harvest receding ice would be pointless; no one with any sense would undertake any such project, climate change or no climate change, except where sea ice is plentiful and preferably forming actively and surviving unmelted for at least three seasons. Nor would it necessary to create any local disturbance to assess the promising areas, because prospecting would generally be done by satellite rather than by ship – simply for reasons of speed, broad perspective, and economy.

It might seem perverse to the point of insanity to propose harvesting sea ice during polar winters, but I submit that the incentives of extra cold, and the associated ease of harvesting, stowage, and refining, should make it rewarding to design the equipment and to plan the operations to exploit just such profitable insanity. That it also would be beneficial from the ecological viewpoint would be welcome, though incidental, so there should be little need to police the operations for good practice.

All this of course, refers mainly to sea ice and pack ice sheets. Ice floes and icebergs would have their own considerations, including the fact that for the same volumes of ice they involve tens to hundreds of times smaller areas than floating sheet ice. Harvesting such masses, if practical at all, would have correspondingly smaller effects on the ecology beneath. Floating ice islands such as those of the Antarctic are another matter: they are so episodic that it is hard to take them seriously as long-term ecological concerns anyway. On the other hand, there accordingly is no reason to spare them from exploitation. Besides, mass for mass, they too would cover smaller areas than ordinary sea ice.

If instead, a good case could be made for conserving the ice islands, the logical response would be to tether sufficiently large islands to the mainland ice sheet to conserve them for seasons, perhaps indefinitely. Then they would be spared from harvesting. Such tethering even might cause them to re-attach to the land-bound ice shelf.

Should tethering not strike anyone as attractive, then the floating shelf should certainly be harvested as expeditiously as possible; the valueless melting of an ice island is in the words of a great thinker: “a pernicious interference with the laws of Nature”; it would affect larger areas than ice harvesting would cover for years. The process of uncontrolled melting would kill all sorts of organisms where the island drifted and melted, marooning polar organisms in lower latitudes where they would die. And that happens every few years, when new ice islands break off and drift northwards.

Far rather harvest the ice as soon and as completely as possible, before it got into hot water, where it would leave its passengers to their fates. And much the same could be said of icebergs.

Another real-world aspect that is emerging as I write, is that melting of large areas of ice sheets is causing a great deal of concern in some circles —informed circles in particular. As the sheets melt on land or slide into the ocean, they raise the ocean level accordingly. No surprise: this has happened in the past, with ocean levels fluctuating by hundreds of metres over geological periods. And the changes of ocean level that we calculate at present are slight: of the order of a few metres — say five or ten.

The catch is that the number of people whose lives and livelihoods are within say, ten metres of mean sea level, is huge. Not only are there may inhabited islands that would disappear entirely, but entire countries could vanish. Even some states, like Florida and Louisiana could become history, leaving the likes of the United States with an internal refugee problem of the order of many millions; we could yet see Mexico refusing to take refugees from the United States.

Now, that particular topic is huge and complicated and of great intrinsic interest in its own right, but does not primarily have much to do with fresh water supplies, so I shall not discuss it here, but one immediate point is that every bit of ice shelf that we remove as it approaches the sea, whether from Greenland or Antarctica, will tend to a net improvement of the situation, rather than aggravation.

So at the very worst, that concern does not militate against the harvesting of polar fresh water.

And when there is no more ice?

A king ordered his wisest man to prove his wisdom by teaching a horse to talk.
The man acceded, but said it would take at least five years.
Privately he explained to despairing friends:
"If I had refused he certainly would have killed me at once.
As it is, I have five years in which anything may happen.
The horse might die. The king might die. I might die.
And besides, who knows? I never have tried any such thing;
perhaps in five years I can teach the horse to talk."

Traditional parable

Some people object that to harvest ice would be futile in the long term: Anthropogenic Global Warming will soon eliminate sea ice and eliminate ice from Greenland and the Antarctic. That is as may be, but even Anthropogenic Global Warming will not change the inclination of the Earth's axis by much, and it follows that winter will not be abolished. In fact, even if sea ice eventually melts disastrously and completely in each subpolar region every summer, which is by no means certain, and even if no form of engineering could mitigate the effects, which is positively unlikely, there should be large quantities of rain, snow, and sea ice within each polar circle every winter.

Young sea ice to be sure, but we already have contemplated means for exploiting it.

For one thing, the hotter the summers, the greater the humidity will be, and somewhere there must be matching precipitation in the cooler regions. Where the precipitation would occur is a different question, and all sorts of engineering schemes might be necessary for capturing rain and snow by other means than exploiting sea ice, but as long as there is precipitation and freezing wherever there is a polar night over polar seas, we can be confident of finding or making fresh or brackish ice. In fact, if suitable quantities of suitable quality do not form spontaneously, we could have ice harvesters and factories covering square kilometres of ocean in strips, collecting the ice for much of the year, and refining it for the rest of the year.

And in such conditions the value of ice deliveries, rather than water deliveries, would be all the greater.

Anthropogenic Global Warming would be seen as disastrous in most contexts, but to prevent it or at least mitigate it, and ultimately to exploit it, would be in the finest traditions of the achievements of human hubris.

Ice, Infrastructure, and Commitment

If you’re achieving all your goals, you’re not setting them aggressively enough.
Laszlo Bock

We have known for generations that, short of a pandemic causing a few billion deaths, the need for fresh water can only grow. Certainly in our traditional consumption of fresh water there is scope for water savings, for avoiding and ameliorating pollution and water loss, for using water more intelligently, and equally certainly we need to improve our practice accordingly, but that scope is limited. Besides, if you look into the real prospects and the requirements for those necessary measures, you find that on any major scale they are neither easier nor cheaper than anything so far discussed in this essay. Furthermore, water is needed for so many things, power, irrigation, industry, as well as domestic supply, that we cannot simply go out and collect whatever we want for any particular use: almost any water we divert to alleviate one need aggravates some other need or interferes with some other function or increases some other cost.

Our immediate problem is not to find more water; the planet has plenty for our next few centuries. What we do need is to find the largest immediate uncommitted source that we can afford to exploit without harming other interests. Salt water is plentiful, but expensive to purify, even though we have made massive improvements in desalination. Anything we can do to decrease the energy cost of obtaining fresh water is worth looking into.

Now, natural processes continuously desalinate water in quantities greater than we yet have any need for, and they even store a lot of it for us in the form of ice and dispense that ice in quantities greater than we need at any particular time. Pack ice drifts till it melts, and glaciers dribble gradually into the ocean or down rivers.

Rain and snow in temperate regions are another matter, but they already are largely claimed by various legal parties, except when they present threats of floods or mudflows. Even when we do not use them all, we cannot simply take more, or we conflict with downstream users in one way or another. For instance, some rivers simply get used (even re-used) completely. Examples include the Colorado river. Others get too polluted to be of use to downstream users. Damming of the Nile has practically destroyed the Mediterranean sardine fishing industry off the Nile delta, and it prevents the annual Nile silting. And worse is in store: with more damming, as is currently underway, the Nile as we know it might yet cease to exist within our children's lifetime.

Trouble is brewing around our major rivers and lakes. If you dam water you cover land. If you fail to dam water, and you decrease flood control options. Use accumulated water for power and you limit its scope for irrigation, industrial, and domestic use. And whenever you empty dams you create other problems.

In short we need fresh water from elsewhere. We know where most of our surface fresh water is. We know that it is frozen, and generally the frozen water is far from where we want it. Proposals for using it have so far been pathetically naïve, for instance dragging icebergs over the ocean. Fair enough, ideas have to start from somewhere, but such non-starters have given the feasibility of exploiting sub-polar ice a bad name.

This essay has argued that there is scope for taking the harvesting of sub-polar ice seriously as a source of water, and in fact, that such an industry is inevitable and could be developed within a matter of years.

The obstacles are:

It does not sound possible (much as undersea oil drilling was dismissed when the idea was proposed)
It will not be as easy as its proponents make it sound
It will take heavy investment, and in particular it will be costly to start up as an industry
On anything but a huge scale it never will be worth while, let alone economical
Harvesting and transporting the ice, whether solid or molten, will be only part of the problem; dealing with it at the point of delivery is no trivial matter either
Design of the harvesting, transport, delivery and application technology involves whole ranges of different problems; we cannot simply think up a bright idea and expect it to work economically first time, quite apart from the problem of producing trained staff to run the industry

In short, humanity needs to generate start-up capital and infrastructure, and possibly the development of international legal standards as well. National commitments might be necessary to encourage development. People rarely understand the scope and importance of infrastructure, so pioneers tend to come up with half-baked ideas that crash ignominiously.

Conversely, other people stand abashed at the scale of start-up challenges, and proclaim every form of new development impossible.

It is a shame and an indictment that some of the most spectacular of our multi-billionaires, who squander huge sums on space tourism and similar gambles, cannot instead spend much less on a far more profitable and beneficial new industry.

But it is worth repeating: our exploitation of natural ice as a source of water is not a matter of whether, but of when and how. It is high time to think it over at levels of authority sufficient to invest resources in the development of pioneering plans and equipment.

Full Duplex

Thursday, March 8, 2018

Water on the Rocks