On thin ice

Using new data from the European Space Agency's CryoSat satellite spanning 10 years, an international team of scientists has discovered an alarming rate of loss for the Arctic sea ice. Satellites whose mission is to closely watch variations in the coverage and thickness of polar ice show the volume of Arctic sea ice declined an astounding 36 percent during autumn and 9 percent during winter between 2003 and 2012.

The past six years have seen the lowest summer ice extent in three decades, according to the international team of scientists led by University College London, reaching the lowest levels last September at about 3.61 million square kilometers.

To measure the volume of Arctic ice, CryoSat's radar altimeter beams pulses of microwave energy towards the ice, bouncing waves off both the top sections of ice and through the cracks to the water below. The difference in height between these two surfaces allows scientists to calculate the "freeboard" -- the height of ice above the water -- and, as a result, the volume of the ice coverage.

This graphic shows data collected from NASA ICESat, ESA CryoSat, and Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) on sea ice thickness in the Arctic. Figure (a) shows the 2003-2007 average ICESat ice thickness for October/November and (b) the 2004-2008 average for February/March. Figures (c) to (f) are measurements based on CryoSat data -- for October/November 2010 (c), February/March 2011 (d), October/November 2011 (e) and February/March 2012 (f). The final two figures are based on PIOMAS measurements for October/November 2011 (g) and February/March 2012 (h).