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How Much Ice Is Vanishing? You Don’t Want to Know

There isn’t a doubt in the world (among serious scientists, anyway) that the sea has been rising for the past century, by about eight inches in total since 1900. There’s little doubt, either, that the rise has been speeding up over the past couple of decades — the water has been inching up about as twice as fast lately as it was for most of the 20th century.

All of that is a powerful confirmation of what thermometers tell us: that the Earth is warming — the result, say those same serious scientists, of human-generated, heat-trapping greenhouse gases. That heat makes seawater expand, and it also transforms land-based ice into even more water that swells the oceans further.

The mountain ice in the Himalayas (pictured above), Karakorams and other high ranges to the south of the Tibetan plateau, a region so icy it’s sometimes called the “third pole", has lost only about 1% of the worldwide total. Credit: TopTenList.org

What nobody has firmly pinned down so far, though, is just how big a contribution all that new water makes to the rising seas. They’ve come up with an estimate, by calculating how much should come from heat expansion then blaming the rest on melting ice: about 1.8 millimeters per year, says University of Colorado physicist John Wahr. But that’s not as convincing as a direct measurement, and it doesn’t solve the mystery of where all the ice is disappearing from.

Now, however, thanks to Wahr and three other scientists, the measurement question and the mystery have both been answered. Using a high-flying pair of satellites known collectively as GRACE, the Gravity Recovery and Climate Experiment mission, they’ve been watching carefully since 2002 to see, among other things, which of the planet’s glaciers and ice sheets are shrinking and by how much. The answer, just reported in Nature: between 2003 and 2010, about 385 billion tons of ice have vanished into the sea each year — enough, says Wahr, “to fill Lake Erie with water eight times over, or cover the entire U.S. with water to a depth of a foot and a half.”

As it turns out, that comes pretty close to what the estimators were saying before GRACE weighed in. That’s a good thing, since it means ice and sea-level experts were on the right track. They were also right that the greatest contribution by far is coming from the huge masses of ice sitting atop Greenland and Antarctica.

Average changes in ice thickness in centimeters per year from 2003 to 2010, as measured by NASA’s Grace satellites, in each of the world’s ice caps and glacier systems outside of Greenland and Antarctica. Blue represents ice mass loss, while red represents ice mass gain. Credit: NASA/JPL-Caltech/University of Colorado

But there was one big surprise: the mountain ice in the Himalayas, Karakorams and other high ranges to the south of the Tibetan plateau — a region so icy it’s sometimes called the “third pole" — has lost only a paltry 4 billion tons of ice annually over the study period, or about 1% of the worldwide total. It was, said Wahr, “a big surprise” that it was so little, and that the bulk of the loss outside Antarctica and Greenland is coming from other mountain ranges. But then, previous estimates of ice loss in that region have been based on very limited measurements on the ground, and weren’t trusted all that much in the first place.

Aside from that, the new, more reliable numbers on ice loss won’t give much comfort to those who have something to fear from the rising sea, which means hundreds of millions of people living in coastal cities around the world, from New York to Shanghai to Amsterdam to Calcutta. For the people who live on the Indian subcontinent and Southeast Asia, though, the news may be a little rosier: the great rivers that water the region have their source in those same high mountains. If the ice that feeds those rivers is mostly staying intact, there’s less chance that the rivers will start to run dry.

But while the new research finally nails down what’s been happening during the past decade or so, Wahr warns that it doesn’t necessarily tell us what will happen in the future. “In 2004,” he says, “glaciers in southeast Greenland suddenly started moving faster toward the sea. Then they stopped, and glaciers in the north and west started to speed up.” The GRACE measurements will help scientists monitor future changes more accurately, but for now they’re just the beginning of the biggest wild card in figuring out how high, and how fast, the sea will rise.

Related Video: 

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How Do We Know: Greenland’s Melting Ice Sheet

Comments

By Mark McCaffrey (Oakland, CA 94609)
on February 13th, 2012

What an odd headline: “How Much Ice Is Vanishing? You Don’t Want to Know”.

Why wouldn’t I want to know?  Such encouragement of denial is part of the problem we face toward having an adult conversation… and we’ve been in the dark too long about how much ice is melting and how much sea level can be expected to rise in coming decades and centuries.  Should we prepare for a foot or so by 2100?  A meter?  More? These are questions that planners in coastal regions are wrestling with.  The amount of ice and thermal expansion is certainly something areas in the US like Miami and the Bay and Sacramento/Central valley of California have to plan for. 

I realize headlines are not always written by the author, but it’s unfortunate to have Climate Central encouraging denial by that headline, which obviously is not the intent of the article.

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By Robin Parsons (Kingston Ontario Canada )
on February 13th, 2012

Perhaps the reason why the Himalayan ice is not metling as quickly is simply elevation as CO2 is a heavier than air gas thusly tending to trap more heat at ground levels than at elevation - add into that the heat from the earth’s interiour heat bleed getting further trapped by the now insulating heavier layer of warm air - CO2 - hence more ground level heating - less at elevation

Reply to this comment

By Jason Box (Columbus, OH, 43201)
on February 13th, 2012

The graphic presented is misleading to the not very careful readers, as it does not include/feature the larger combined losses from Greenland and Antarctica. While you acknowledge this point in the text and caption, the ice sheets graphic should be included alongside.

Nice post otherwise.

Jason E. Box, PhD
Assoc. Prof., Department of Geography, Byrd Polar Research Center
The Ohio State University, Columbus, Ohio, USA
Tel. +1 614 506 0830
http://bprc.osu.edu/~jbox/
http://twitter.com/climate_ice

Reply to this comment

By Andrew
on February 13th, 2012

Jason - the graphic comes from NASA JPL, and we clearly indicate that it does not include ice losses from Greenland and Antarctica. So I don’t think it is misleading, but you’re right that it does present an incomplete picture of ice mass loss worldwide.

While the study included an estimate of the contribution to sea level rise from all glaciers and ice sheets (including Greenland and Antarctica), it mainly focused on the contribution to sea level rise from non-polar ice caps and glaciers.

For readers interested in a graphic that includes the melting from Greenland and Antarctica, it can be found here: http://www.jpl.nasa.gov/news/news.cfm?release=2012-036#2.

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By Chris Squire (Twickenham UK)
on February 13th, 2012

What Wahr actually says is: ”˜ . . The total contribution to sea level rise from all ice-covered regions is thus 1.48”‰Ã‚±”‰0.26”‰mm”‰Ã¢ÂˆÂ’1, which agrees well with independent estimates of sea level rise originating from land ice loss and other terrestrial sources.’ NOT 1.8.

What he actually meant to say was ’ . .  ”˜ . . The total contribution to sea level rise from all ice-covered regions is thus 1.48”‰Ã‚±”‰0.26”‰mm”‰YR−1, . . ‘

http://www.nature.com/nature/journal/vaop/ncurrent/full/nature10847.html#/ref6

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By steve jones (santa cruz/california/95060)
on February 13th, 2012

Great article!
Yes, the Ice is melting FAST everywhere.
Particularly appreciated your analysis on the “third pole” in the tibetan plateau.
We need to all collectively act FAST if we are to avert further planetary damage to the biosphere.

Regards,

Steve Jones
Global Environmentalist
Santa Cruz, California USA

My Online Book:
SAVING THE PLANET:
http://pulsar774.tripod.com

———————————————————————————————————

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By mlemonick
on February 14th, 2012

I have to take issue with Mark McCaffrey about the headline. It may well be that those who are absolutely wedded to climate denial will find some fodder here, but for those people, anything at all, including a grocery list, is fodder for their beliefs.

For the vast majority of people with normal reading comprehension, the phrase “you don’t want to know” is a lighthearted way of saying “there’s bad news here.”

I for one refuse to avoid all colloquialisms lest someone choose to misinterpret them. Climate scientists and those of us who write about their work have enough nonsense to deal with. We don’t need to become stiff and humorless on top of everything else.

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By turner bain (Dowling Park, FL 32460)
on February 15th, 2012

I would have passed over this article if it had not had the hook ‘...you don’t want to know.’  People need to lighten up lest the conversation at the table turns to more pleasant topics, such as ‘wan’t it nicely warm this winter?’.

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By Alex Smith (Vancouver, Canada)
on February 16th, 2012

Listen to fresh interviews of 3 scientists on “the Arctic emergency”:

Dr. Carlos Duarte, award winning Spanish oceanographer and Polar expert;
Dr. Peter Wadhams, head of the Polar Research unit at Cambridge University; and
Dr. David Archer from the University of Chicago, carbon and methane expert.
Radio Ecoshock 1 hour.
http://bit.ly/A2aJno

Find a 5 page blog summary with links here:
http://www.ecoshock.info/2012/02/arctic-emergency-global-threat.html

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