The AP ran an article, Dubai firm dreams of harvesting icebergs for water.
That’s an old idea that someone may make feasible some day. Or not.
But I was struck by this sentence.
What exactly does he mean by this?
WAG perhaps there’s a lot of air in the ice, like how melting a fist-sized snowball doesn’t produce very much water.
Icebergs tend to be very dense - ice that’s been compacted under nearly geological pressures, sometimes for millennia. I am not sure of the exact mechanism since neither water nor ice compress, but I’d guess it means all air and gases have been squeezed out. I have heard, purely anecdotally, that iceberg chips last much longer in drinks than any manufactured ice.
Maybe that’s what was meant in that garbled quote.
I read the article, and that sentence made me do a double-take also. It makes no sense. Ice shouldn’t vary all that much in how much water it produces. Ice bergs originate from glaciers and may have some impurities such as rock dust, so they will produce somewhat less water than pure ice of the same volume, but the difference should usually be trivial.
Glacial ice is pretty compressed and should have relatively little air in it. It should also be denser than sea ice that freezes directly from the sea and still has brine in it.
Moving to GQ.
That’s what I thought. I have no idea what the hell that guy is talking about.
Then again, who the hell is Robert Brears and Mitidaption and why should we listen to them about anything? I’ve not been able to find anything about them via Google that did not originate from them.
There must be some sort of translation or transcription error there–it makes no sense. While googling around I did find this interesting article at The Atlantic, though.
Maybe they are making a reference to “dry ice”, frozen carbon dioxide, which when melted leaves no water at all. It a significant component of icebergs is trapped pockets of frozen carbon dioxide, then there would be reduced water resulting from the melting of a specific quantity of ice.
No, icebergs are not cold enough to contain frozen CO[SUB]2[/SUB].
There is no dry ice in icebergs. Carbon dioxide freezes at −109.3 °F (−78.5 °C). While colder temperatures have been recorded on the central plateau in Antarctica, an iceberg floating in seawater would be equilibrating to the temperature of the water, far far warmer than that.
Its because the ice has different densities. Just like what was said “WAG perhaps there’s a lot of air in the ice, like how melting a fist-sized snowball doesn’t produce very much water.”
Here is some links:
http://chemistry.elmhurst.edu/vchembook/122Adensityice.html
http://www1.lsbu.ac.uk/water/ice_phases.html
So you could suck on this ice on the Antarctic ice shelf itself and get not a lot of water out of it, unlike an ice cube from your fridge
Its because the ice has different densities. Just like what was said “WAG perhaps there’s a lot of air in the ice, like how melting a fist-sized snowball doesn’t produce very much water.”
Here is some links:
http://chemistry.elmhurst.edu/vchemb...ensityice.html
http://www1.lsbu.ac.uk/water/ice_phases.html
So you could suck on this ice on the Antarctic ice shelf itself and get not a lot of water out of it, unlike an ice cube from your fridge
Your links provide no support for this assertion. Your first link merely provides the commonly known information that ice is less dense than water. Your second link is to a description of various exotic phases of ice that can form under high pressure and low temperature conditions. These would not occur in icebergs. (I also note that these exotic phases are virtually all more dense than normal ice, and so would produce more water when melted, not less.)
This site suggests that there’s a fairly thick layer of firn on top of a glacier, which is better thought of as compressed snow than ice:
It seems plausible that your average glacier could consist of a lot of firn, since it’s generally going to be what’s at the edge.
Though…one possibility is that there’s good business in scamming rich people in the desert about how ice works.
I figure that someone oddball enough to seriously suggest such a scheme would make oddball statements.
The two issues are mass and density. It doesn’t matter what form the ice is in, virtually all the mass is going to be just water for a Antarctic glacier-origin berg.
Density can be an issue since the lower the density the higher the volume which impacts towing costs. But it’s really just the density below the water line that matters. Any light fluffy stuff on the surface isn’t going to much affect towing outside of possibly increasing wind resistance which is far less an issue than water resistance. In fact, a fluffy coating on top provide better insulation and reduces losses during towing.
But the ice below the water line isn’t going to be all that fluffy. A piece from an Antarctic ice shelf is going to quite dense at that level.
This wouldn’t really be the case in Antarctic or Greenland icebergs, though, - in general, only the freeboard is snow + firn, and everything below the waterline (i.e. most of the 'berg) is ice. This only gets worse as the surface layers melt preferentially over the subsurface ice.
Per your own Cite.
Then consider the average Antarctic ice sheet thickness is >2km, but firn-ice transition depth in West Antarctica is ~60m…“a lot of firn” doesn’t seem like a good description.
All that air should provide some insulation. Some of the schemes have included covering bergs with insulating blankets. If it was fluffy like that below the water I’d think it would soak up a lot of seawater and rapidly melt away a lot of volume.
Overall I wonder if any iceberg towing schemes are more practical than just loading a tanker with ice. And that assuming desalination isn’t practical enough already.
“You could melt a lot of this ice and get very little water from it.”
the only way I can parse that as making any sense, assuming that it was just poor wording, rather than just outright stupidity, is an efficiency argument.
I don’t know costs involved, but transporting icebergs to the equator is probably very energy intensive, and I assume that a substantial amount of the iceberg is lost on the trip.
So, in that case, much of the iceberg melts on the way, and you get very little water from it. Poorly phrased, and maybe not what he meant, but to be as generous as possible, that would be my interpretation.
I am suspecting some sort of translation/language issue. But it’s still hard to figure out what might have been meant, with any and all corrections applied.
The largest tanker can haul 318,000 metric tons. The article talks about an iceberg that is 20 billion gallons. At 8.34 pounds/gallon that’s 168 billions pounds or 76,203,609 metric tons. That’s 240 tanker trips.
But getting ice into a tanker is not easy. Tankers haul liquids. Breaking up 318,000 metric tons of ice into a form a tanker could haul would take a lot of time and energy in Antarctic conditions. Nor could you do it from the edges where the bergs are: you’d have to do mining on the shelf over a broad area because you’d be skimming the surface to get the equivalent volume held under water. I’m not sure how far inland you’d have to go to find a stable site. Maybe you’d have to build a pipeline to the coast.
I think that’s an even worse idea than trying to tow a calved berg. Once you get the nets on it and overcome the inertia of something that size, if you can, you’re in far better shape with one ocean trip.