Arctic sea ice has thinned dramatically

Arctic sea ice thinned dramatically between the winters of 2004 and 2008—NASA

Analysis of data from a NASA Earth-orbiting spacecraft shows that “Arctic sea ice thinned dramatically between the winters of 2004 and 2008, with thin seasonal ice replacing thick older ice as the dominant type for the first time on record.”  The latest discovery “provide further evidence for the rapid, ongoing transformation of the Arctic’s ice cover.”

ICESat measures the distances to the top of the snow cover and to the sea surface. The difference between the two quantities gives the total “freeboard” measurement; that is, the amount of ice above the water line relative to the local sea level. Credit: Courtesy of Norbert Untersteiner, University of Washington

NASA says their and the University of Washington in Seattle researchers carried out “the most comprehensive survey to date using observations from NASA’s Ice, Cloud and land Elevation Satellite, known as ICESat,” to determine “the first basin-wide estimate of the thickness and volume of the Arctic Ocean’s ice cover.”  Their research team, led by Ron Kwok of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., published its findings on July 7 in the Journal of Geophysical Research-Oceans.

This schematic shows the geometric relationship between freeboard (the amount of ice above the water line), snow depth, and ice thickness. Buoyancy causes a fraction (about 10 percent) of sea ice to stick out above the sea surface. By knowing the density of the ice and applying “Archimedes’ Principle” — an object immersed in a fluid is buoyed up by a force equal to the weight of the fluid displaced by the object — the total thickness of the ice can be calculated. Credit: Ron Kwok, NASA/JPL

ICESat measurements of winter multi-year ice cover in the Arctic Ocean between 2004 and 2008, along with the corresponding downward trend in overall winter sea ice volume, and switch in dominant ice type from multi-year ice to first-year ice. Credit: Ron Kwok, NASA/JPL

ICESat measurements of winter multi-year ice cover in the Arctic Ocean between 2004 and 2008, along with the corresponding downward trend in overall winter sea ice volume, and switch in dominant ice type from multi-year ice to first-year ice. Credit: Ron Kwok, NASA/JPL

Data visualization of Arctic sea ice thickness, as measured by ICESat, shows the decline of the thickest ice (white, 4 to 5 meters thick) and increase in thinner ice (deep blue, 0 to 1 meter) from 2003 to 2008. Credit: NASA Goddard’s Scientific Visualization Studio.

Data visualization of ice thickness, as measured by ICESat, shows the yearly growth (winter) and retreat (fall) of ice in the Arctic Ocean. Credit: NASA Goddard’s Scientific Visualization Studio

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Related Links:

• Arctic Sea Ice Reaches Lowest Coverage For 2008
• Satellites Show Arctic Literally on Thin Ice

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