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Antarctic Ice Melt: The Big Picture

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First complete map of the speed and direction of ice flow in Antarctica, derived from radar data from Japanese, European, and Canadian satellites, and processed by NASA-funded research. The thick black lines delineate major ice divides. Subglacial lakes in Antarctica's interior are also outlined in black. Thick black lines along the coast indicate ice sheet grounding lines. Credit: NASA/JPL-Caltech/UCI 

The vast ice sheets that cover Antarctica are sliding inexorably into the sea. This is hardly news: it was happening last year, and in 1900, and thousands — even millions — of years before that. The slide is so slow that it’s balanced, more or less, by new ice built from the snow that falls every year. If that balance were to shift dramatically, sending all the ice into the ocean, sea level would shoot up by a catastrophic 200 feet or so.

That’s not likely to happen any time soon (“soon” being the next few hundred years, at the very least). But the flow of ice has accelerated in recent years, both in Antarctica and in Greenland, and scientists who study moving ice are understandably anxious to figure out how that trend will play out during the coming decades. Back in 2007, the U.N. Intergovernmental Panel on Climate Change's (IPCC) last major report deliberately left out changes in the rate of ice sheet flow from its calculations for future sea-level rise, because scientists simply didn’t have enough information to say anything reliable.

But a new map, just published online by the journal Science, may help change that. It doesn’t provide any firm answers. But it does give scientists a detailed look at how, where, and how fast ice flows across the continent today — and that will be a crucial piece of information for monitoring changes over the coming years.

The map, compiled by Eric Rignot and his colleagues at the University of California, Irvine, assembles radar measurements from five different satellites that have crisscrossed the frozen continent from 1996 to 2009. Each satellite alone gives only part of the picture. But together, they show the entire continent in motion — in some places, slowly, in others much more quickly. There’s an impressive animation from the website of the Jet Propulsion Laboratory, which conducted much of the data analysis.

What’s significant here, says Rignot, is that the classical model of Antarctic ice flow has it all happening by deformation — the weight of the ice pressing down and literally squeezing itself out from the thickest points at the center of the continent (they’re brown on the image below) toward the sea. “But the only way you can explain these long, fast-flowing fingers,” he says (they’re red and purple here) “is that ice is sliding along the bedrock.”

Understanding these details, he says, fills in a major missing piece of the puzzle regarding how ice drains from Antarctica, and future versions of the map will show how that drainage may accelerate in a warming world. That most likely won’t happen due primarily melting, since the Antarctic interior will remain frigid for hundreds of years to come. The more important factor will be the warming of ocean waters, which melt ice shelves and glacial tongues that reach into the sea.

With those natural brakes removed, upstream ice can flow faster — quickening the pace of sea level rise. “Information about what the ocean is doing, both here and in Greenland, is still a missing piece of the puzzle,” says Rignot. “We need to know what impact that’s having on outlet glaciers, and how that will change in the future.”

Comments

By Raveendran Narayanann (NYC. NY)
on August 19th, 2011

” Not only iceshelves can be collapsed by SUN but also concentrated Deicers can also Deices Iceshelves. 2008 was Solar Minimum year. Wilkins collapsed during Winter of 2008. Jones Iceshelf also collapsed. IS IT SUN?
Mushrooming of Desalination systems in the Middle East started during 1985. 2*C also started to rise later on.Those Desalters dumping Millons of Tons of concentrates & Chemicals 24/7 basis to Oceans & Seas.
By strict Regulations & Enforcements by errecting Zero Discharge Systems ( ZDS ) capture concentrates. Thereby more icemass will grow.Automaticaly 2*C will come down. No sea level rise. Thereby Airconditioning of Mother Earth. Also welcome to visit Sarva Kala Vallabhan Group in fb & comment “

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By Karl (Springfield VT, 05156)
on August 20th, 2011

Thanks for the great analysis. 

I just wanted to mention; assuming that the climate change needed to melt the ice in Antarctica and Greenland will be hundreds of years in the future is not a valid extension of the data.  If the change thats been happening is in fact a gradual linear change, then yes, it probably will be hundreds of years before the oceans are 200 feet higher.  But if the change is happening in an exponential fashion then massive ice melt could happen much much faster and sooner. 

Given that past climate change has happened in fits and spurts I think its reasonable to assume that we can’t really know how fast or how long it will take the ice to melt.  I suspect it will melt much faster than many think.  I hope I’m wrong.

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By Robert (Marsing / Idaho / 83639)
on October 15th, 2011

Something is happening much faster than previously predicted. We are witnessing a dramatic loss of Arctic ice and it’s my understanding we are on the verge of an ice free Arctic. If the Arctic goes than so will Greenland which is an archipelago. An ice free Arctic will cause ocean waters to warm exponentially and Greenland will disintegrate.

A warming ocean means an overall warming environment and Antarctica will greatly be impacted.
Hundreds of years? I strongly disagree. The topographical maps of Greenland show large amounts of water under it’s surface, if Greenland were solid mass than it would be a much more stable environment but it’s not. When Greenland goes, it’s over.

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By steve (stockton calif 95206)
on December 31st, 2011

We live on a world that is, by its very nature, cyclic. I’ve read, heard about and viewed information on other web sites which seem to be jumping up and shouting that the warming trend touted is not, in fact, happening. That may be so.

But a wise man will not negate the words or thoughts of another without seeking a similar truth. Bottom line is that although the warming trend we currently observe can be deemed a consequence of man’s activities or only a temporary situation that holds no problems for future generations. In either case it seems that a prudent man would remain cautious regardless of circumstance. In this way do we protect our heritage.

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