Arctic Ocean Is On Thin Ice

 

Animation showing changes in monthly Arctic sea ice volume using data from ESA’s CryoSat-2 (red dots) and estimates from the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) (solid line) for the 2011 and 2012 winter growth periods (October – April). 

Credit CPOM/UCL/ESA/UW-APL/NSIDC/Planetary Visions

They found that from 2003 to 2008, autumn volumes of ice averaged 11,900 cubic kilometers (2,855 cubic miles) But from 2010 to 2012, the average volume had dropped to 7,600 cu. km. (1,823 cu. mi.) a decline of 4,300 cu. km (1,032 cu. mi.) The average ice volume in the winter from 2003 to 2008 was 16,300 cu. km. (3,911 cu. mi.), dropping to 14,800 cu. km (3,551 cu. mi.) between 2010 and 2012 – a difference of 1,500 cu. km. (360 cu. mi.).

‘The data reveals that thick sea ice has disappeared from a region to the north of Greenland, the Canadian Archipelago, and to the northeast of Svalbard,’ says Dr Katharine Giles, a research fellow at the Centre for Polar Observation and Modelling at University College London (UCL) and a member of the scientific team.

Combining the UW model and the new satellite observations suggests the summer minimum in Arctic sea ice is one-fifth of what it was in 1980, when the model begins

“Other people had argued that 75 to 80 percent ice volume loss was too aggressive,” said co-author Axel Schweiger, a polar scientist in the UW Applied Physics Laboratory. “What this new paper shows is that our ice loss estimates may have been too conservative, and that the recent decline is possibly more rapid.”

The system developed at the UW provides a 34-year monthly picture of what’s happening to the total volume of Arctic sea ice. The Pan-Arctic Ice Ocean Modeling and Assimilation System, orPIOMAS, combines weather records, sea-surface temperature and satellite pictures of ice coverage to compute ice volume. It then verifies the results with actual thickness measurements from individual moorings or submarines that cruise below the ice.

“Because the ice is so variable, you don’t get a full picture of it from any of those observations,” Schweiger said. “So this model is the only way to reconstruct a time series that spans multiple decades.”
The Polar-5 aircraft, carrying the EM instrument that was used to validate Cryosat-2 sea ice thickness measurements, flying over the validation site. 

Credit: NERC/UCL/Rosemary Willatt

Giles and her colleagues report their findings in a paper that has been accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union. AGU has posted the manuscript online as an accepted article.

The findings confirm the continuing decline in Arctic sea-ice volume simulated by the Pan-Arctic Ice-Ocean Modelling and Assimilation System (PIOMAS), which estimates the volume of Arctic sea ice and had been checked using earlier submarine, mooring, and satellite observations until 2008.

Other satellites have already shown drops in the area covered by Arctic sea ice as the climate has warmed. Indeed, sea-ice extent reached a record minimum in September 2012. But CryoSat-2, launched in April 2010, differs in that it lets scientists estimate the volume of sea ice – a much more accurate indicator of the changes taking place in the Arctic.

Credit: NERC/UCL/Seymour Laxon

‘While two years of CryoSat-2 data aren’t indicative of a long-term change, the lower ice thickness and volume in February and March 2012, compared with same period in 2011, may have contributed to the record minimum ice extent during the 2012 autumn,’ says Professor Christian Haas of York University, Canada Research Chair for Arctic Sea Ice Geophysics, co-author of the study and coordinator of the international CryoSat sea ice validation activities.

CryoSat-2 measures ice volume using a high-resolution synthetic aperture radar altimeter, which fires pulses of microwave energy down towards the ice. The energy bounces off both the top of sections of ice and the water in the cracks in between. The difference in height between these two surfaces let scientists calculate the volume of the ice cover.

The team confirmed CryoSat-2 estimates of ice volume using measurements from three independent sources – aircraft, moorings, and NASA’s Operation IceBridge.

The research was funded by the Natural Environment Research Council, the European Space Agency, the German Aerospace Center, Alberta Ingenuity, NASA, the Office of Naval Research and the National Science Foundation.