Geophysical Research Letters, Vol. 35, L20502, doi:10.1029/2008GL035417, 2008
Mass balance of the Greenland ice sheet from 1958 to 2007
E. Rignot (Department of Earth System Science, University of California, Irvine, California, USA; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA), J. E. Box (Byrd Polar Research Center, Ohio State University, Columbus, Ohio, USA), E. Burgess (Department of Geography, University of Utah, Salt Lake City, Utah, USA), and E. Hanna (Department of Geography, University of Sheffield, Sheffield, UK)
We combine estimates of the surface mass balance, SMB, of the Greenland ice sheet for years 1958 to 2007 with measurements of the temporal variability in ice discharge, D, to deduce the total ice sheet mass balance. During that time period, we find a robust correlation (R2 = 0.83) between anomalies in SMB and in D, which we use to reconstruct a continuous series of total ice sheet mass balance. We find that the ice sheet was losing 110 ± 70 Gt/yr in the 1960s, 30 ± 50 Gt/yr or near balance in the 1970s–1980s, and 97 ± 47 Gt/yr in 1996 increasing rapidly to 267 ± 38 Gt/yr in 2007. Multi-year variations in ice discharge, themselves related to variations in SMB, cause 60 ± 20% more variation in total mass balance than SMB, and therefore dominate the ice sheet mass budget.
Received 21 July 2008; accepted 22 September 2008; published 22 October 2008.
Key words: glaciology, mass balance, sea level
Index Terms: 0720 Cryosphere: Glaciers; 0726 Cryosphere: Ice sheets; 0762 Cryosphere: Mass balance (1218, 1223); 1621 Global Change: Cryospheric change (0776); 1620 Global Change: Climate dynamics (0429, 3309).
Citation: (2008), Mass balance of the Greenland ice sheet from 1958 to 2007, Geophys. Res. Lett., 35, L20502, doi:10.1029/2008GL035417.
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2 comments:
You should read these aswell:
http://www.sciencedaily.com/releases/2008/11/081114191911.htm
http://www.newscientist.com/article/dn16026-humans-may-have-prevented-super-ice-age.html
And the reaction from James Hansen on the "Humans may have prevented super ice age" article:
James E. Hansen, NASA Goddard Institute for Space Studies:
Look at Figure 3 in our “Target” paper Target CO2: Where should humanity aim? [pdf]. Yes, the Earth has been on a 50-million-year cooling trend with superposed glacial-interglacial oscillations.* It would take only a small further reduction in climate forcing (less long-lived GHGs or whatever) to yield more ice during the glacial phase of glacial-interglacial oscillations. But that is entirely academic at this point, unless humans go extinct. Although orbital variations instigate the glacial-interglacial swings, the mechanisms for climate change are changes in GHG amount and surface albedo (as we show in Fig. 1 of our paper) — those mechanisms are now under the control of humans. Another ice age cannot occur unless humans go extinct. It would take only one CFC factory to avert any natural cooling tendency. Our problem is the opposite: we cannot seem to find a way to keep our GHG forcing at a level that assures a climate resembling that of the past 10,000 years.
Jim
*The long-term cooling is related to the situation with the continents — not much subduction of carbonate-rich ocean crust now. The site of strong subduction associated with India plowing through the Tethys Ocean ended when India crashed into Asia 50 million years ago, so that source of CO2 diminished.
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