Greenland ice sheet melting faster
Thursday, 10 August 2006
Marie Theresa Bray
Cosmos Online
SYDNEY, 10 August 2006: The Greenland ice sheet is now melting three times faster than predicted, making the likely rise in sea levels this century larger than originally feared, according to a U.S. study published today.
In a study published in the online issue of the U.S. journal, Science, Jianli Chen and colleagues at the University of Texas in Austin have calculated that the Greenland ice sheet has been melting at an accelerated rate since 2004.
"A direct consequence of the significant melting would be the global sea level rise," said Chen. "This melting alone will contribute about 0.6 millimetres a year of the global sea level rise.
"If the Greenland cap melted completely, it would raise global mean sea level by about 6.5 metres. If this was to occur, most of the world's coastal regions would be subject to flooding," the authors wrote.
Previously Jonathan Gregory, a climatologist at Britain's University of Reading, and Philippe Huybrechts, a glaciologist at the Free University in Brussels, Belgium, had warned in a 1999 study of the possible meltdown of the Greenland ice sheet. It appears these concerns were not unfounded.
Chen and his colleagues used data collected by a pair of satellites known as the Gravity Recovery and Climate Experiment (GRACE) to accurately measure gravity changes as a function of time. They analysed data collected on the gravity variation over Greenland, and then compared the monthly data of the ice sheet between April 2002 and November 2005 for the study.
"These time-variable gravity changes [from GRACE] can be used to compute mass changes, such as ice melting or accumulation on the Earth surface," said Chen. "In this sense, GRACE 'directly' measures ice mass change on a monthly basis."
The researchers now estimate that about 240 cubic kilometres of the ice sheet is disappearing annually. This is a staggering three times faster than the rate estimated in the past five years.
The difference in estimates can be attributed to increased melting in the past one and a half years and, most importantly, to the improved filtering and estimation techniques from GRACE.
If these findings are validated, it will significantly strengthen the case of the effect of global warming and would show that melting polar ice sheets are a contributing factor to global sea level rise. According to the Chen, these findings can be used for further studies on the ice sheet.
"This is just one of many encouraging finds we are seeing from GRACE," added Chen. "After a few more years, with more GRACE data collected, we anticipate to have a much convincing conclusion and clearer picture of Greenland ice mass balance."
Greenland boasts the second largest ice cap on Earth at 3.000 metres in height. It also contains about 2.5 million cubic kilometres, or 10% of the world's total ice mass.
http://www.cosmosmagazine.com/node/539
Informant: binstock
Marie Theresa Bray
Cosmos Online
SYDNEY, 10 August 2006: The Greenland ice sheet is now melting three times faster than predicted, making the likely rise in sea levels this century larger than originally feared, according to a U.S. study published today.
In a study published in the online issue of the U.S. journal, Science, Jianli Chen and colleagues at the University of Texas in Austin have calculated that the Greenland ice sheet has been melting at an accelerated rate since 2004.
"A direct consequence of the significant melting would be the global sea level rise," said Chen. "This melting alone will contribute about 0.6 millimetres a year of the global sea level rise.
"If the Greenland cap melted completely, it would raise global mean sea level by about 6.5 metres. If this was to occur, most of the world's coastal regions would be subject to flooding," the authors wrote.
Previously Jonathan Gregory, a climatologist at Britain's University of Reading, and Philippe Huybrechts, a glaciologist at the Free University in Brussels, Belgium, had warned in a 1999 study of the possible meltdown of the Greenland ice sheet. It appears these concerns were not unfounded.
Chen and his colleagues used data collected by a pair of satellites known as the Gravity Recovery and Climate Experiment (GRACE) to accurately measure gravity changes as a function of time. They analysed data collected on the gravity variation over Greenland, and then compared the monthly data of the ice sheet between April 2002 and November 2005 for the study.
"These time-variable gravity changes [from GRACE] can be used to compute mass changes, such as ice melting or accumulation on the Earth surface," said Chen. "In this sense, GRACE 'directly' measures ice mass change on a monthly basis."
The researchers now estimate that about 240 cubic kilometres of the ice sheet is disappearing annually. This is a staggering three times faster than the rate estimated in the past five years.
The difference in estimates can be attributed to increased melting in the past one and a half years and, most importantly, to the improved filtering and estimation techniques from GRACE.
If these findings are validated, it will significantly strengthen the case of the effect of global warming and would show that melting polar ice sheets are a contributing factor to global sea level rise. According to the Chen, these findings can be used for further studies on the ice sheet.
"This is just one of many encouraging finds we are seeing from GRACE," added Chen. "After a few more years, with more GRACE data collected, we anticipate to have a much convincing conclusion and clearer picture of Greenland ice mass balance."
Greenland boasts the second largest ice cap on Earth at 3.000 metres in height. It also contains about 2.5 million cubic kilometres, or 10% of the world's total ice mass.
http://www.cosmosmagazine.com/node/539
Informant: binstock
rudkla - 11. Aug, 10:59
