Published on May 4th, 2011 | by Joshua S Hill
Continuing Decrease in Sea Ice Extent
NASA satellite imagery shows us just how much sea ice is being lost compared to the average in the Arctic.
The image contains two parts, on the left showing sea ice concentrations in the Arctic for September, 2010, which represents the annual minimum, and on the right showing concentrations for March, 2011, representing the annual maximum.
The yellow outline on both images represents the average median sea ice extent observed by satellite sensors in September and March for the period 1979 to 2000.
Arctic sea ice reached its minimum extent – extent being the total area with an ice concentration of at least 15 percent – on September 19, 2010, at 4.60 million square kilometres, or 1.78 million square miles. This brought 2010 in as the third lowest Arctic sea ice extent in the satellite record.
The maximum sea ice extent took place on March 7 of this year, at 14.56 million square kilometres, or 5.62 million square miles, bringing it in according to NSIDC figures as the second lowest sea ice extent for the month of March in the satellite record.
These figures only continue the March trend in sea ice extent which has been decreasing at a rate of 2.7 percent per decade.
There is a little bit of good news in the data, however, as it appears that the amount of older and thicker ice has increased slightly over the last year. This is good news, because older and thicker has a better chance of surviving the summer.
“Data through the third week of March shows an increase in sea ice one to two years old, and older than two years old, compared to recent years,” NSIDC noted. “However, the amount of older ice remains much lower than in the mid-1980s, and there is still almost none of the oldest ice (older than four years) that used to dominate much of the Arctic Ocean.”
The maps were compiled from observations by the Defense Meteorological Satellite Program and by the Advanced Microwave Scanning Radiometer for EOS (AMSR-E), on NASA’s Aqua satellite. The sensors measure microwave energy radiated from Earth’s surface, as sea ice and open water emit microwaves differently.
Source: NASA Earth Observatory