Visualization of Arctic sea ice thickness in 2008. The white patches are 13-16' thick, deep blue are 0-3' thick.
New satellite data from NASA confirms what research released a couple months of go said regarding the thinning of Arctic sea ice. Namely that it has thinned dramatically in the past four years and that for the first time in recorded history seasonal sea ice cover has replaced multi-year ice as the dominant ice type. In fact, multi-year ice cover the size of the Alaska has been lost just between 2004-2008:
The same visualization as above, for 2004
NASA says that by using ICESat measurements they have determined that overall Arctic sea ice thinned by about 7" per year, resulting in a total loss over the past four winters of 22.2". Additionally, the total area of multi-year ice cover has shrunk by 42%.
Multi-year sea ice is on average 9' thick, while seasonal ice cover is on average 6' thick.
Recent Warming to Blame
The reason this thinning of ice cover is happening is because, in short, ice losses in the summer have been so great that winter ice replacement has been insufficient to replace those losses. NASA attributes this "to the recent warming and anomalies in sea ice circulation."
ICESat measurements of the distribution of winter sea ice thickness over the Arctic Ocean between 2004 and 2008, along with the corresponding trends in overall, multi-year and first-year winter ice thickness. Image: 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. Image: Ron Kwok, NASA/JPL
New Data Will Help Predict When Ice-Free Arctic Summer Will Occur
Ron Kwok of NASA's Jet Propulsion Laboratory explains the significance of this new data:
Ice volume allows us to calculate annual ice production and gives us an inventory of the freshwater and total ice mass stored in Arctic sea ice. Even in years when the overall extent of sea ice remains stable or grows slightly, the thickness and volume of the ice cover is continuing to decline, making the ice more vulnerable to continued shrinkage. Our data will help scientists better understand how fast the volume of Arctic ice is decreasing and how soon we might see a nearly ice-free Arctic in the summer.
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