Clearest evidence yet of polar ice losses
(30 November 2012)
An international team involving Durham University experts has produced the most accurate assessment of ice losses from Antarctica and Greenland to date, ending 20 years of uncertainty.
In a landmark study, published on 30 November in the journal Science, the researchers show that melting of the Antarctic and Greenland ice sheets has contributed 11.1 millimetres to global sea levels since 1992. This amounts to one fifth of all sea level rise over the survey period.
About two thirds of the ice loss was from Greenland, and the remainder was from Antarctica.
Although the ice sheet losses fall within the range reported by the IPCC in 2007, the spread of the IPCC estimate was so broad that it was not clear whether Antarctica was growing or shrinking. The new estimates are a vast improvement (more than twice as accurate) thanks to the inclusion of more satellite data, and confirm that both Antarctica and Greenland are losing ice.
The study also shows that the combined rate of ice sheet melting has increased over time and, altogether, Greenland and Antarctica are now losing more than three times as much ice (equivalent to 0.95 mm of sea level rise per year) as they were in the 1990s (equivalent to 0.27 mm of sea level rise per year).
Professor Mike Bentley, from the Department of Geography, said: "This study is a big step forward because there are several ways to measure change in the Antarctic and Greenland ice sheets and it shows clearly that the different techniques come up with essentially the same answer."
The Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE) is a collaboration between 47 researchers from 26 laboratories, and was supported by the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA).
The study, which combines observations from 10 different satellite missions to develop the first consistent measure of polar ice sheet changes, was led by the University of Leeds and NASA’s Jet Propulsion Laboratory.
The researchers were able to reconcile the differences between dozens of earlier ice sheet studies through careful use of matching time periods and survey areas, and by combining measurements collected by different types of satellites.
Study coordinator, Professor Shepherd, from the University of Leeds, said: "The success of this venture is due to the cooperation of the international scientific community, and due to the provision of precise satellite sensors by our space agencies. Without these efforts, we would not be in a position to tell people with confidence how the Earth's ice sheets have changed, and to end the uncertainty that has existed for many years."
The study also found differences in the pace of change at each pole.