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Archive for the ‘greenland’ Category

Greenland Glacier Slides Much Faster in Summer

Posted by feww on May 10, 2010

Greenland glacier slide 220 percent faster in summer: Study

In case anyone doubted the obvious, researchers in Scotland have quantified the differential in the rate of slide of Greenland glacier. The movement of ice sliding down toward the sea is 220 percent faster in summer than in winter, they said.


You think it’s fun to swim in slushy ice water instead of walking on firm ice? Photo Credit: Dan Crosbie (public domain). Click image to enlarge.

The researchers say recent observations of Greenland glacier movement highlighted significant seasonal differences.

Greenland, the world’s second biggest ice sheet after Antarctica, could raise sea levels globally by about 6.7  meters (22 ft) if it melted.

GPS satellite measurements of the glacier movement in south-west Greenland showed that the ice in some places is sliding at 300 meters per year during summer.

“Our measurements reveal substantial increases in ice velocity during summer, up to 220 percent above winter background values,” the study reported.

What if the temperatures were getting warmer all year round?


The map shows temperature changes for the last decade — January 2000 to December 2009 — relative to the 1951-1980 mean. Warmer areas are in red, cooler areas in blue. The largest temperature increases occurred in the Arctic and a portion of Antarctica. (Image credit: NASA). Click image to enlarge.


Arctic Temperatures Trend 1987-2007 Using Satellite Data 1981-2007. Source: NASA

The researchers attribute the summer slide to melt water pooling under the ice.

“In a warming climate, with longer and more intense summer melt seasons, we would expect that water will reach the bed farther inland and a larger portion of the ice sheet will experience summer velocity changes.” The study says.

The study was published in the journal Nature Geoscience on Sunday.


Click image to enlarge.


Greenland Melt Extent, 2005: Konrad Steffen and Russell Huff – Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado at Boulder

Greenland Ice Sheet

The Greenland ice sheet is a massive glacier (body of ice)  covering more than 1,700,000 square kilometers (664,235 sq miles), which used to cover about 80% of Greenland’s land surface.


Chenega Glacier is an active glacier in Prince William Sound, on the Kenai Peninsula in Alaska. Source: DOI, US Gov.


Chenega Glacier located in the Chugach National Forest, Chugach Mountains, Prince William Sound.Photo Dated 17 June 2004. Source: US Fish and Wildlife Services. Click image to enlarge.

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Posted in Arctic Temperature Trend, Chenega Glacier, Climate Change, greenland, Greenland ice sheet | Tagged: , , | Leave a Comment »

Who is afraid of melting ice sheets?

Posted by feww on April 18, 2009

Based on its outdated “one-dimensional” model, the U.N. Climate Panel has reported that seas could rise by 18-59 cm  (7-24 inches) by 2100. The model also excludes the threat from highly probable scenarios in which ice sheets in Antarctica and Greenland could melt at exponential rates.

Ian Allison, head of  the Australian Antarctic Division’s Ice, Ocean, Atmosphere and Climate program was asked by Reuters the following question: How great is the threat from melting ice sheets?

Allison who is a researcher within the Antarctic Climate and Ecosystems Cooperative Research Center, and who has been involved in Antarctic science for more than 4 decades, responded as follows.

HOW GREAT IS THE THREAT FROM ICE SHEETS MELTING?

I think it is now unequivocal that warming of the world is occurring and I think the last IPCC (Intergovernmental Panel on Climate Change) conclusively showed that a major cause of warming is greenhouse gas emissions from mankind.

We now know that the ice sheets are contributing to sea level rise and for the Arctic, at least, this is because the warming of this region is much greater than in other places on Earth.

We also know that glaciers in mountain areas are undergoing a very rapid retreat and they’re a major contributor of sea level rise, too.

WHICH IS OF MORE CONCERN? GREENLAND OR WEST ANTARCTICA?

Greenland is of more concern because of the warming of the Arctic. Greenland is at lower latitude than much of Antarctica and we’ve seen the direct effect of the melting.

We still don’t understand many things about the dynamic response of the ice sheets but we do see direct melt exceeding snowfall in Greenland.

This might not mean a runaway effect but it does mean Greenland is contributing to sea level rise and will continue to add to sea levels at the present temperatures for many hundreds of years.”

EXPLAIN THE THREAT FROM WEST ANTARCTICA

Ice shelves and floating ice tongues can buttress the flow of grounded ice from the interior of the ice sheets. We’ve seen examples in both Greenland and Antarctica of floating ice disappearing, and the ice that sits on the land then flowing more quickly into the ocean.

“In addition, the West Antarctic may be inherently unstable. The West Antarctic forms what is called the marine ice shelf. The ice is resting on bedrock but that bedrock is below sea level. It’s like if you load too many ice cubes in your gin and tonic, the bottom one touches the bottom of the glass even though it’s well below the water level.

Where the bedrock under a marine ice sheet slopes down toward the interior, such as under parts of West Antarctica, the ice sheet may be unstable. If it thins, it will start to float at the edges, becoming an ice shelf.

For a bedrock that slopes backwards and becomes deeper further in, continued retreat of the grounded ice sheet may proceed very rapidly. A small retreat could in theory destabilize the entire West Antarctica ice sheet, leading to rapid disintegration.

WHAT ARE THE MAIN GAPS IN OUR KNOWLEDGE?

There two areas. One, we need to improve our mathematical models of ice streams, ice sheets and ice shelves to be able to better project future changes. We also need more detailed measurements of how deep the bedrock is under the ice sheets to use in the models.

The other major gap in our understanding is what is happening at the bed of the ice sheets; how they react with liquid water at the base, what role water may have in sliding processes and the role of gravels and slurry at the base.

We now know there is a lot of liquid water under the ice sheets. But we don’t really know how changes in this may affect the ice flow. Knowing what’s under the ice sheets we really need to measure that with radar systems.

WHAT ARE YOUR MAIN MESSAGES TO POLICY MAKERS?

The main thing is monitoring what’s actually happening with sea level rise and the ice sheets. We’ve now got tools that can do that, we can improve those and make sure they keep going, particularly satellite-based systems.

We need better predictive tools to know just what is likely in the next 100 years. I don’t think we should be rushing into building up coastal defenses until we know what we could be defending against. So our biggest requirement is to be able to refine our projections for what may happen in the future. (Edited by David fox).

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Posted in CO2 Emissions, greenland, IPCC, mathematical models of ice melt, West Antarctica | Tagged: , , , , | 2 Comments »