The ice in Greenland and the Arctic is melting even faster than first anticipated, raising sea levels as much as 1.6 meters (five feet) by the end of the century.
The new estimates come from the Arctic Monitoring and Assessment Program, the scientific division of the Arctic Council, a group of eight nations that have interests in the region. AMAP's assessments will be presented to representatives of the member nations, including the U.S., next week at a conference in Greenland. It is also being discussed this week at a scientific conference in Copenhagen.
The new estimates draw on several recent studies and new techniques. The last major assessment of sea level rise was made in 2007, by the U.N.'s Intergovernmental Panel on Climate Change. That report said there were, broadly speaking, two possibilities by the year 2100. One is for 18 to 38 centimeters (7 to 15 inches) and the other is for 26 to 59 centimeters (10 to 23 inches).
The new studies point to sea level rise at nearly twice that rate, at 90 to 160 centimeters (35 to 63 inches). That is enough to put much more pressure on low-lying areas in the U.S. such as Cape Cod, Florida and New Orleans.
The AMAP assessment finds that Greenland is losing ice faster between 2004 and 2009 - up to four times faster than in the 1995-2000 span.
A number of recent published studies have pointed to an increased melt rate in Greenland. For example, in January, research at the Cryospheric Processes laboratory at the City College of New York showed that the 2010 melting index of ice in Greenland had broken a previous record, set in 2007.
There has also been more attention paid to the role of the ice sheets on the smaller islands in the Canadian far north. Alex Gardner, a research fellow in the Department of Atmospheric, Oceanic and Space Sciences at the University of Michigan, found that in the five-year period from 2004-2009 the region lost 7 cubic miles of water per year on average. The rate for just the last two years - 2007-2009 - was even higher, at 22 cubic miles per annum.
The Canadian Arctic has only one third of the Earth's land ice, but combined with the mountain glaciers in other regions accounts for half of the ice melt in the world. The other half is from the Greenland and Antarctic ice sheets.
The AMAP report may further underscore the urgency of reducing greenhouse gas emissions. The Arctic environment, many scientists note, is especially sensitive to increases in global average temperature. Many species of animal, such as polar bears, there depend on ice being present in the water for a certain amount of time during the year.