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Global warming: CU-led study pinpoints Earth’s ice loss

Arctic sea ice extent is below average in early February, according to the National Snow and Ice Data Center.

New data to help project sea level rise

By Summit Voice

Earth’s glaciers and ice caps outside of the regions of Greenland and Antarctica are shedding about 150 billion tons of ice annually, according to a new study led by the University of Colorado Boulder.

The total mass ice loss from Greenland, Antarctica and all Earth’s glaciers and ice caps between 2003 to 2010 was 1,000 cubic miles, about eight times the water volume of Lake Erie.

“The total amount of ice lost to Earth’s oceans from 2003 to 2010 would cover the entire United States in about 1 and one-half feet of water,” said CU-Boulder physics Professor John Wahr, who helped lead the study.

The research effort is the first comprehensive satellite study of the contribution of the world’s melting glaciers and ice caps to global sea level rise. The results indicate all the melted ice is raising sea levels by about 0.4 millimeters annually, said .

The measurements are important because the melting of the world’s glaciers and ice caps, along with Greenland and Antarctica, pose the greatest threat to sea level increases in the future, Wahr said.

The researchers used satellite measurements from the Gravity Recovery and Climate Experiment (GRACE) to calculate that the world’s glaciers and ice caps lost about 148 billion tons, or about 39 cubic miles of ice annually from 2003 to 2010. The total does not count the mass from individual glacier and ice caps on the fringes of the Greenland and Antarctic ice sheets, which could add up to an additional 80 billion tons.

“This is the first time anyone has looked at all of the mass loss from all of Earth’s glaciers and ice caps with GRACE,” said Wahr. “The Earth is losing an incredible amount of ice to the oceans annually, and these new results will help us answer important questions in terms of both sea rise and how the planet’s cold regions are responding to global change.”

The findings will be published in the Feb. 9 online edition of the journal Nature. Lead author Thomas Jacob did his research at CU-Boulder and is now at the Bureau de Recherches Géologiques et Minières, in Orléans, France. Other paper co-authors include Professor Tad Pfeffer of CU-Boulder’s Institute of Arctic and Alpine Research and Sean Swenson, a former CU-Boulder physics doctoral student who is now a researcher at the National Center for Atmospheric Research in Boulder.

“The strength of GRACE is that it sees everything in the system,” said Wahr. “Even though we don’t have the resolution to look at individual glaciers, GRACE has proven to be an exceptional tool.” Traditional estimates of Earth’s ice caps and glaciers have been made using ground-based measurements from relatively few glaciers to infer what all of the unmonitored glaciers around the world were doing, he said. Only a few hundred of the roughly 200,000 glaciers worldwide have been monitored for a decade or more.

The vast majority of climate scientists agree that human activities like pumping huge amounts of greenhouse gases in the atmosphere is warming the planet, an effect that is most pronounced in the polar regions.

One unexpected study result from GRACE was that the estimated ice loss from high Asia mountains — including ranges like the Himalaya, the Pamir and the Tien Shan — was only about 4 billion tons of ice annually. Some previous ground-based estimates of ice loss in the high Asia mountains have ranged up to 50 billion tons annually, Wahr said.

“The GRACE results in this region really were a surprise,” said Wahr. “One possible explanation is that previous estimates were based on measurements taken primarily from some of the lower, more accessible glaciers in Asia and were extrapolated to infer the behavior of higher glaciers. But unlike the lower glaciers, many of the high glaciers would still be too cold to lose mass even in the presence of atmospheric warming.”

“What is still not clear is how these rates of melt may increase and how rapidly glaciers may shrink in the coming decades,” said Pfeffer, also a professor in CU-Boulder’s civil, environmental and architectural engineering department. “That makes it hard to project into the future.”

According to the GRACE data, total sea level rise from all land-based ice on Earth including Greenland and Antarctica was roughly 1.5 millimeters per year annually or about 12 millimeters, or one-half inch, from 2003 to 2010, said Wahr. The sea rise amount does include the expansion of water due to warming, which is the second key sea-rise component and is roughly equal to melt totals, he said.

“One big question is how sea level rise is going to change in this century,” said Pfeffer. “If we could understand the physics more completely and perfect numerical models to simulate all of the processes controlling sea level — especially glacier and ice sheet changes — we would have a much better means to make predictions. But we are not quite there yet.”

Background

Launched in 2002, two GRACE satellites whip around Earth in tandem 16 times a day at an altitude of about 300 miles, sensing subtle variations in Earth’s mass and gravitational pull. Separated by roughly 135 miles, the satellites measure changes in Earth’s gravity field caused by regional changes in the planet’s mass, including ice sheets, oceans and water stored in the soil and in underground aquifers.

A positive change in gravity during a satellite approach over Greenland, for example, tugs the lead GRACE satellite away from the trailing satellite, speeding it up and increasing the distance between the two. As the satellites straddle Greenland, the front satellite slows down and the trailing satellite speeds up. A sensitive ranging system allows researchers to measure the distance of the two satellites down to as small as 1 micron — about 1/100 the width of a human hair — and to calculate ice and water amounts from particular regions of interest around the globe using their gravity fields.

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18 Responses

  1. It’s pretty amazing what these satellites can do, as well as provide a picture too. All this information being beamed back here, to be assembled into creating a picture, be it visual or written, allows us to get a better understanding of our environment. Each day, we seem to emerge from the dark ages of understanding.

  2. “Greenland and Antarctica are shedding about 150 billion tons of ice annually,”

    Hm, sounds like alot of ice is melting.

    But lets look at it another way, 150 billion tons of ice is roughly 150 cubic kms of ice. Antarctica has 30 million cubic km of ice and Greenland has an aditional 2.8 million cubic kms of ice.

    So out of 32 million cubic km of ice, only 150 melts every year. That is such a relativley tiny amount, I’m not entirely convinced that it can accurately be measured.

    At this rate it will take over 200,000 years to melt away. That’s almost enough time for two more global glaciations.

    I think we still have enough time.

    cheers

  3. If sea levels rose 1/2 inch in 8 years, at that rate the total sea level rise over the next 88 years will still be only about 1/2 a foot. That means that in 2100 AD you won’t even notice the change that has occurred in a hundred years. Why are you trying to scare people? Given that Antarctic land ice is increasing and that accounts for 90% of the earth’s land-based ice, it’s likely that the sea level rise rate will stay at current levels or go down. Clearly there is no serious threat for the foreseeable future.

    • First, sea level rise is accelerating. Best guess is about 3 feet in a century.

      Second, even a couple of inches is going to be significant because that is a lot more water to add to high tides, storm surges etc where a few inches overall will mean much more at individual events and places.

      The actual science suggests that all this will be a serious threat for many in the near future.The increase in flooding events over the last few years suggests this may have already started.

    • “That means that in 2100 AD you won’t even notice the change that has occurred in a hundred years.”

      Exactly right, no one noticed the change over the last 100 years and they didn’t notice the change thousands of years before that.

      It is the business of environmentalists to scare everyone. If you believe their stories, you’ll give over control of your life to their ‘safe keeping’. As if they have a clue.

      Thank god I’m not an environmentalist anymore.

  4. [...] worldwide meltdown of earth’s glaciers and ice caps (not including Greenland and Antarctica) was 150 billion [...]

  5. What klem is missing here is that we are approaching a tipping point, after which the warming will be difficult or impossible to stop. The polar ice caps reflect light and heat back into space, whereas the dark oceans absorb it. As the ice caps shrink, less light is reflected and more absorbed, so that the planet warms even more, shrinking the ice caps even more. Permafrost then thaws, releasing more carbon into the atmosphere, trapping more heat, and warming the planet still more. It is these looming feedback loops that we need to prevent, and Hansen and others fear we may trigger them by 2016.

    • OMG, not the famous tipping point thing again. Lol!

      They keep telling us that the tipping point is only a couple of years away, then when it does not materialize the tipping point is bumped ahead another few years, then bumped again.

      I think the last tipping point was 2012 just in time for Kyoto, now it is 2016 just in time for Kyto’s replacement. No coincidence there. Lol!

      I’m not missing anything pal. You are.

  6. We seem to think about changes only during our lifespan.
    Here is a thought. It is believed the last major ice age ended about 10 to 12 thousand years ago. Left behind was lake Agassi, many times larger than the total of the Great Lakes. In Minnesota the Glacier had cut out the land and left over 10,000 Lakes. The Minnesota River now at best is a comparative trickle perhaps at most 100 ft wide compared to the deep and miles wide great river Warren which flowed north into Lake Agassi. The Glaciers did not recede of course, they just melted. But considering the distances between the edges of glaciers and time elapsed, the receding would have been more than two feet per day!!
    Paleoclimatology to include all histories including that of human endeavors resulting from climatic changes should be a part of the background study of those who profess to be climatologists. The more one analyzes events, the more one realizes that there is nothing unusual or extreme about current weather conditions.

  7. Incidentally, 0.4mm annually would be less that two inches per century.

  8. Bob, you’re a spoil sport.

    • Of course thermal expansion is going to be the far greater cause of sea level rise. I was only referring to the apparent notions of extreme sea level rise noted in this article as a result of glacial and other non sea ice melt (sea ice melt would not raise sea level)
      I left to check current sea level changes and changes in SST’s You might want to check for yourself

  9. [...] Global warming: CU-led study pinpoints Earth’s ice loss (summitcountyvoice.com) [...]

  10. If “global warming” is melting the Arctic, why is there extra ice nearly everywhere like the Bering Sea, Baffin Bay, Sea of Okhotsk? Strange that GW only seems to affect the Barents sea? Or is it because differences in ice area are due more to wind and currents. Of course, the second test that fails here is the flat global temperatures for the last 15 years according to satellites.

    How much fail can this theory withstand?

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