Data from NASA's Ice, Cloud and land Elevation Satellite (ICESat), the European Space Agency's CryoSat-2, airborne surveys and ocean-based sensors show that the volume of Arctic sea ice declined 36 percent in autumn and 9 percent in the winter in 2012, breaking the record for the highest extent of melting over the warmer months.
CryoSat and ICESat use sea ice freeboard - ice floating above the ocean's surface - to calculate the thickness of the ice. Previous data from submarine and satellite data confirms that computer models showing a decline in sea ice volume helped build a record of changes over several decades.
Researchers found that from 2003 to 2008, the average volume of autumn ice was 2,855 cubic miles, but from 2010 to 2012, the average dropped to 1,823 cubic miles, a difference of 1,032, NASA's Jet Propulsion Laboratory reported.
The study was funded by an international consortium consisting of the United Kingdom's National Environmental Research Council, the European Space Agency, the German Aerospace Center, Alberta Ingenuity, NASA, the Office of Naval Research and the National Science Foundation, led by Seymour Laxon of University College London.
It was important to obtain more information because CryoSat-2 is a relatively new and untested instrument, and ICESat was decommissioned in 2009. Scientists cross-referenced data from ICESat and CryoSat-2 with measurements obtained in a study through NASA's Operation IceBridge (NASA's project tasked with bridging the data gap between ICESat and ICESat-2's launch in 2016), ocean-based sensors and another European airborne survey.
The study showed more ice melt in the autumn than predicted from the Pan-Arctic Ice-Ocean Modeling and Assimilation System (PIOMAS) which was used to predict Arctic sea ice volume, but less of a difference than predicted in winter months. "It's important to know because changes in volume indicate changes in heat exchange between the ice, ocean and atmosphere," said Nathan Kurtz, a scientist at NASA Goddard Space flight center.
While very little of this is new information in the grand scheme of things (researchers have warned for years that melting Arctic sea ice could pose grave consequences for many regions that are close to sea level), the precise measurements can help scientists estimate the extent and urgency of the decline.
