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Reduction of Ice Cover at High Latitudes - Media Telecon Site
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Summary of Waleed Abdalati’s presentation:
Dr. Abdalati will present recent findings on the acceleration of Greenland’s glaciers, the shrinking of Canada’s ice cap, and reduction of ice cover in Alaska. Accelerated rates of change in these high latitude regions have resulted in a greater regional contribution to sea level.
Image 1: Jakobshavn Glacier Retreat 2001-2004
Greenland’s Jakobshavn Glacier, the fastest moving glacier in the world, has retreated approximately 7 km in the past three years, which is believed to have contributed to a rapid acceleration of the glacier. Click on image to view animation. Credit: NASA/USGS
Image 2: Greenland’s Fastest Glacier Doubles Speed
The Jakobshavn Glacier’s 2003 velocity (in blue) is nearly double its 1992 velocity (in red). Click on images to view animation. Credit: NASA/USGS
Image 3: Break-up Causes Acceleration Upstream
As the Jakobshavn Glacier discharges ice from its mouth, tributary ice streams show signs of acceleration. 2002 image series shows rapid migration of ice features downstream, triggering adjacent land ice to accelerate downslope. Click on image to view animation. Credit: NASA/USGS
Image 4: Greenland Ice Changes 1997 – 2003
The following image shows rates of elevation change in Greenland measured along aircraft flight lines during 1997-2003, superimposed on a map of measurements from 1993-1999. Warm colors indicate elevation loss and cool colors represent elevation gain. Dark areas of red and blue indicate the highest rates of change, -/+60 cm/year respectively. Credit: NASA
Summary of Joey Comiso’s presentation:
Dr. Comiso will discuss dynamic changes in Arctic perennial sea ice cover and its relationship to temperature change. Comiso’s research estimates that Arctic perennial sea ice has decreased at a rate of 9% per decade and ice-atmosphere feedbacks associated with reflectivity may result in further change.
Image 5: Arctic Perennial Sea Ice Decreasing 9% Per Decade
Annual minimum sea ice extent and concentration for 25 years, 1979 to 2004. Click on image to view animation. Credit: NASA
Image 6: 22 Year Satellite Record Shows Warming In the Arctic
Arctic surface temperature trend, 1981-2003. Warming in the Arctic is asymmetrical, with the most significant warming (in gold) over much of North America and some areas of cooling (in blue) over Eurasia. Click on image to enlarge. Credit: NASA
Summary of Ted Scambos’ presentation:
Dr. Scambos will show how melting and ice flow in glacier systems in the Antarctic Peninsula have greatly increased in recent years. According to Scambos, the rapid pace of glacial changes associated with warming implies that significant increases to the rate of sea level rise are a more likely possibility than previously thought.
Image 7: Larsen Ice Shelf Break-Up, 2002
Over the course of three months in early 2002, Antarctica’s Larsen B Ice Shelf broke into many pieces, releasing several thousand square kilometers of ice into the ocean, and causing acceleration of adjacent glaciers. Click on image to view animation. Credit: NASA
Image 8: Larsen Ice Shelf Acceleration
As the Larsen Ice Shelf retreats, the surrounding glaciers respond and accelerate downstream. This acceleration is often coupled with a change in elevation which can be measured by a laser altimeter such as the GLAS instrument on the ICESat satellite. Click on image to enlarge. Credit: NSIDC
Image 9: Why Glaciers Accelerate
Diagram shows how warm summer temperatures can lead to seasonal acceleration of Antarctic glaciers and occasionally result in rapid ice shelf disintegration. Removal of the ice shelf causes increased glacier acceleration by reducing the forces that counteract glacier flow. Click on image to enlarge. Credit: NSIDC