Arctic sea ice volume has declined by 36 per cent in the autumn and 9 per cent in the winter between 2003 and 2012, a UK-led team of scientists has discovered.
Researchers from the Centre for Polar Observation and Modelling at UCL used new data from the European Space Agency’s CryoSat-2 satellite spanning 2010 to 2012, and data from NASA’s ICESat satellite from 2003 to 2008 to estimate the volume of sea ice in the Arctic.
The team, led by Professor Seymour Laxon (UCL Earth Sciences), found that from 2003 to 2008, autumn volumes of ice averaged 11,900 km3. But from 2010 to 2012, the average volume had dropped to 7600 km3 – a decline of 4300 km3.
Average ice volumes in winter from 2003 to 2008 was 16,300 km3, dropping to 14,800 km3 between 2010 and 2012 – a difference of 1500 km3.
“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,” said Dr Katharine Giles (UCL Earth Sciences), who co-authored the report, published online in Geophysical Research Letters.
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 using data from submarine, mooring, and satellite observations.
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.
While the researchers say two years of CryoSat-2 data aren’t indicative of a long-term change, they speculate that the lower ice thickness and volume in winter 2012, compared with winter 2011, may have contributed to the record minimum ice extent during the 2012 autumn.
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 findings are the result of a huge international collaboration between teams from UCL, the European Space Agency, the Jet Propulsion Laboratory, the University of Washington, York University, Alfred Wegener Institute for Polar and Marine Research, Woods Hole Oceanographic Institution, Morgan State University and the University of Maryland.
Professor Seymour Laxon, who was the director of CPOM and principal scientist for several ESA missions, led the study. Tragically, he died in early January. Professor Laxon was part of the UCL team that proposed CryoSat to ESA in 1999, and was a key figure during the development and operational phases of the mission.
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 and the National Science Foundation.
*Source: University College London