Huge Pool of Ice-Free Water Discovered Under Greenland Ice 135
The BBC reports that researchers have discovered a huge pool of meltwater beneath Greenland's ice sheet, trapped "in the air space between particles of ice, similar to the way that fruit juice stays liquid in a slush drink."
From the article, based on research published in Nature Geoscience (abstract): "The scientists say the water is prevented from freezing by the large amounts of snow that fall on the surface of the ice sheet late in the summer. This insulates the water from the air temperatures which are below freezing, allowing the water to persist as liquid all year long. Other researchers believe this discovery may help explain disparities between projections of mass loss by climate models and observations from satellites."
whoosh (Score:5, Informative)
...said the physics teacher.
Under pressure, the freezing point of water is lowered. The more pressure, the lower the ice point. To demonstrate:
Assume that a container is indestructible (let's say, a sphere with a perfect seal). It is full of water with no gas in solution or loose in bubbles or anything like that. Just pure water. Now, stick it in a deep freeze. Wait.
Water has the odd property of expanding at around 4C at normal (sea level) pressure. By the time it freezes at 0C under those same pressure conditions, it has expanded to fill 1/8 more volume than it did as a liquid. This is why icebergs float. This is why distilled water ice cubes also float. The liquid water does its thing and... you know the rest. Titanic.
The water in the sphere is prevented from freezing for the simple reason that it has nowhere to go. It has no space to expand into. If it cannot expand, it cannot freeze. How low can you go? I have no idea, having no access to magnetocaloric equipment. But I daresay, you wouldn't meet the conditions required to get the volume of water to contract to the point where it can solidify in the available space, outside of a suitably equipped laboratory or in the shadow of an outer planet.
Further reading suggests temperatures approaching/lower than about 70K (-203C) to achieve this. Further reading [lsbu.ac.uk].
Re:Right (Score:5, Informative)
it's not true that subsurface water in the Arctic ocean isn't freezing: it is, continually. What salinity does is disrupt the phase equilibrium between liquid and solid so the water phases between solid and liquid at a faster rate than the liquid phasing to solid, ergo the mass remains a liquid. That's only considering salinity. Absent pressure at depth, the entire ocean would be a block of ice right now, but see my other post in this thread (here [slashdot.org]) as to the other reason the Arctic ocean is liquid.
Re:whoosh (Score:4, Informative)
The melting point of water is reduced by 0.007 K per atmosphere of pressure. The effect is of only minor significance, because it is so small. People almost always overestimate it.
If you put water in a real container (as opposed to something indestructible) and put it in the freezer, it will not stay liquid. Instead, it will happily freeze. In doing so it will expand the container, possibly bursting it. To keep the water liquid at just -7 C, you need a container that can withstand 1000 atmospheres, which probably requires a steel pressure vessel. According to the site you linked, there is no pressure sufficient to keep water liquid below -22 degrees.
The pressure under the ice in Greenland is probably about 300 atm at the most (based on the weight of 3 km of ice), so the freezing point is only about 2.1 degrees lower at the bottom than at the top. If there really is pure liquid water at the bottom, that can't be explained purely by regelation. It also has to be quite warm (-2.1 C) at the bottom.
Re:Technolog (Score:5, Informative)
Funny thing is, we have Ice Core Samples [noaa.gov] from all over Greenland, in Multiple Different Databases [noaa.gov] and they have all missed (or misinterpreted) this data for decades. Some of these were 2000 meters deep. In addition there were dye experiments in some areas.
So it is sort of a surprise that we had no hint of this.
Re:why haven't we heard about this before? (Score:4, Informative)
So there was a discrepancy between prediction and observation for the AGW model. Why haven't we heard about that before? Only now that the observations are consistent with theory do we find out about it. Yet more evidence that climate scientists are not real scientists.
What makes you think that scientists have hidden this discrepancy? They haven't, and every anti-AGW promoter has been shouting it from the rooftops (while they ignore or misrepresent all the evidence that supports AGW.)
Re:Technolog (Score:5, Informative)
I'm not surprised. It's science, you keep looking and you keep finding new and interesting things. It's not possible to know everything instantly and Greenland is a remote and expensive place to study.
This water is in the firn [wikipedia.org] which occurs down to a depth of around 50 meters [nationalgeographic.com] before the weight of snow above compresses it to glacial ice which can't hold water like firn. The top of the water table is generally less than 25 meters under the surface (see Figure 2 [nature.com]) and can't be deeper than about 50. These aquifers were found in the far south of Greenland near the coast, one of the warmer areas of Greenland. It's unknown as yet if they exist elsewhere but now they know to look for them. I imagine the further north you get the more difficult it would be for them to form.
So you wouldn't likely see this except possibly at the very top of a 2,000 meter+ ice core. Most of those ice cores are drilled from far higher elevations and further north where it doesn't melt much even in summer so there is little water to begin with and in any case the colder temperatures probably cause water that forms to refreeze near the surface. In order for this water/firn mixture to coexist the temperature has to be just right and it wouldn't take much to tip the balance one way or another. If it tipped to warmer I imagine it could lead to rapid collapse of the snow field but we'll just have to wait and see what happens.
Re:Water to be the new Oil? (Score:5, Informative)
There's lots of fresh water on the planet (including all the fresh water stored as ice). The problem is getting to a place where it's useful. Most places have to make do with the fresh water that's available locally. A notable exception being Southern California which imports water from the north and from the Colorado River. I doubt you'll find knowledgeable people saying fresh water would be completely gone (except perhaps for some overtaxed aquifers). Instead they are saying there will be more demand for fresh water than there is supply available to fill that demand in the future. Getting fresh water from Greenland to any place useful would be difficult and expensive.
Re:Technolog (Score:2, Informative)
And think about it, if scientists came out and said that they had discovered everything that there was to know then they would be putting themselves out of a job.
"Climate change is the biggest issue for us to face this century. It's man made. The science is done. It's complete. It's a matter of political understanding." - Sir David King, UK Government's Chief Scientist, giving evidence to House of Lords select committee (March 2004)
I'm not arguing with you, I'm on your side. Just pointing out that not all scientists have the intellectual honesty we expect.
Re:Hmm (Score:4, Informative)
And yet despite the fact that the global cooling story made the covers of Time and Newsweek in the mid-70's, between 1965 and 1979 there were 6 times as many papers published on global warming from CO2 increases than global cooling in the scientific literature. I was born in 1952 and I don't remember being very alarmed by global cooling in the 1970's.