Is the mass of snow/ice on the Antarctic continent increasing?

Question

I have several times seen the claim that it is? Is this an accepted fact? I would be most grateful for some references. I have heard that global warming in increasing moisture in the air can increase precipitation. Is this a possible cause? Is increasing mass of Antarctic snow/ice (assuming there is an increase) of any significance in terms of possible rises in ocean levels? Is it incorporated into climate models?

Thanks Mr Jello for the comments and reference - interesting picture and text which I would urge people to look at and read.

Thanks Cosmo it is good that people like you are willing to share their understanding of things like this so that people like me can understand a bit better.

Thanks Trevor, as usual a superb answer, it does appear that there is a degree of uncertainty, but I take your word for it that the best estimate is a loss of 82 billion tonnes per year. Must admit though when I did lab experiments we tried to give a possible plus or minus (90% probability) error. Is there any such figure for the 82 billion tonnes?

Thanks Keith P, that completes a collective answer and no-one could ask for more detailed references, and I note that even accounting for possible experimental error measurements indicate a loss of mass. I must admit that on my first reading of Trevor's answer I thought there was someone there counting icebergs or something, I see that it is a lot more sophisticated.

Answer 1

No.

Ice is increasing in the interior, but is being lost at a faster rate on the edges and on the WAIS (West Antarctic Ice Sheet). The net of all changes in Antarctica is a loss of ice mass.

http://www.sciencemag.org/cgi/content/abstract/311/5768/1754
http://icesat.gsfc.nasa.gov/publications/IGS/mass_changes_2005.pdf

Answer 2

Over most of Antarctica, it's "too cold to snow", so warming it up increases snowfall.

This is, as you might imagine, a difficult thing to measure. There are only a dozen or so weather stations on the whole continent. You have to track the altitude of the snow pack over an area the size of North America, with an accuracy of a few millimeters. This is being done to a limited extent by radar from satellite and by accurate GPS measurements in a few spots on the ground, but most of the best geophysical satellites are not on polar orbits and so do not cross Antarctica. The creation and melting of icebergs is episodic, and so yields a noisy signal. I suspect the answer is "we don't really know if Antarctic Ice is increasing or decreasing." The partial answer, based on what studies do exist is: "there are no big changes yet". The study of Antarctic glaciers dates back 30 years at best, and there is little basis of comparison between the past and present. You should understand that most of the continent is little visited, and there are vast areas that have still never seen a human footprint.

The melting of Antarctica is THE big question as far as ocean level rise---the melting of Greenland potentially would contribute a few tens of meters, but the melting of Antarctica would contribute nearly a hundred meters.

The best guess is that as the climate warms, Antarctic ice may increase for a while (couple centuries), perhaps actually lowering the ocean level, then really begin to melt (like Greenland is now), and cause a rapid rise. There is a hypothetical event (qua disaster scenario) called "the collapse of the West Antarctic ice sheet", where basically all the ice in the western half of the continent slides into the ocean over a short period of time (a few centuries). The glaciology of the West Antarctic ice sheet is being studied, but it is too early for any solid conclusions.

Antarctica is an important element in any worldwide climate model.

I point out that the Antarctic ice sheet does not, in general, participate in Ice Ages. These events, being only a few tens of thousands of years long, are not enough to significantly affect the Antarctic ice sheet. The last major change in the Antarctic ice cap was about 30 million (that's million, not thousand) years ago, when the region went from polar rain forest to glacial ice cap.

Answer 3

Excellent question Robert and the short answer is both yes and no.

An increase in average global temps naturally leads to greater evapouration of water from the seas and oceans and consequently to increased precipitation.

Antarctica is technically a desert because, by definition, it receives very little precipitation. What precipitation does fall tends to be as snow and away from the periphery temps never rise above freezing so the snow never melts and, over time, forms ice that eventually makes it's way to the surrounding oceans through glacial creep.

The increased precipitation has led to greater snowfalls in Antarctica and an increase in the overall mass of ice - but only in the 'interior'. Around the periphery the ice is melting at an increased rate, partly due to higher air temperatures and partly due to higher sea temps.

Overall, in 2006, there was a net loss of ice from Antarctica of 82 billion tons, a figure typical of the longer term trend.

In the larger scheme of things this is a relatively small amount and reporesents approx 10% of the annual net global ice loss, the majority coming from the Arctic (600 billion tons) and Greenland (220 billion tons).

In terms of ocean levels, the net ice loss from Antarctica is having a small effect. 82 billion tons (82 cubic kilometres) of water spread across the entire ocean's surface of 375 million square kilometres equates to a very small ocean level rise. In addition to the direct rise caused by meltwater runoff and glacial collapse there's the 'springback' effect caused when the Antarctic landmass rises due to the reduced mass on it's surface. The overall consequence of Antractic melting is an annual contribution to ocean level rises of approx 0.05mm per year. Overall, oceans are rising by 3.1mm a year, primarily as a result of thermal expansion.

To your final point, is it incorporated into climate models? In some of them it is. More recent models are infinitely more sophisticated than those of even a few years ago, with greater computing power and an increased understanding of what's actually happening, more and more variables and other factors are being incorporated into climate models. Today's models are very soiphisticated, some of the earlier ones were about as sophisticated as an abacus and didn't even take clouds into account.

Answer 4

No. The mass of ice has been decreasing since the last ice age.

Any global warming will increase atmospheric moisture. However increased precipipation can in no way compensate for the acccelertion in the melting of icecaps caused by significant incresease in sea temperatures.

Due to changing weather patterns a few glaciers may increase their mass in the short term, but the vast majority are receding rapidly with catastrophic consequences for agriculture in Africa and Asia as rivers and lakes dry up.

Answer 5

I do know that studies have been done showing depletion of mass amounts of arctic ice in Antarctica, but uncertain about snow. Seriously though I don't figure more snow would even matter if ice of more than a thousand years old was breaking off, floating away and melting.

Answer 6

the mass of ice in the polar zones is decreasing, not increasing.
that correlates to average higher sea water temperatures. and the warmer oceans cause more moisture in the air.
warm oceans cause more severe tropical storms, more precipitation, and a change in the division of rain in various climate zones, most of which become wetter but some become drier.
and the additional moisture in the air is itself a catalyst of global warming.

Answer 7

Yes. The ocean levels are increasing. If global warming continues then the ocean levels will increase more and there will be major floods. And soon living things can get extinct.

Answer 8

The mass of snow and ice on the Antarctic is DEcreasing because of the melting ice caps.

Answer 9

Yes I heard it was increasing also, cosmo seems to give a reasonable explaination. From geological records, When Antarctica melts, it does so rapidly. I seems one of those horrible unknowns, which we'll just have to wait and see.

Answer 10

Not right now, the Southern Hemisphere is entering their Spring period.