Mass changes of the Greenland and Antarctic ice sheets and shelves and contributions to sea-level rise: 1992-2002

Changes in ice mass are estimated from elevation changes derived from 10.5 years (Greenland) and 9 years (Antarctica) of satellite radar altimetry data from the European Remote-sensing Satellites ERS-1 and -2. For the first time, the dH/dt values are adjusted for changes in surface elevation resulting from temperature-driven variations in the rate of firn compaction. The Greenland ice sheet is thinning at the margins (-42 � 2G t a -1 below the equilibrium-line altitude (ELA)) and growing inland (+53 � 2G t a -1 above the ELA) with a small overall mass gain (+11 � 3G t a -1 ; -0.03 mm a -1 SLE (sea-level equivalent)). The ice sheet in West Antarctica (WA) is losing mass (-47 � 4G t a -1 ) and the ice sheet in East Antarctica (EA) shows a small mass gain (+16 � 11 Gt a -1 ) for a combined net change of -31 � 12 Gt a -1 (+0.08 mm a -1 SLE). The contribution of the three ice sheets to sea level is +0.05 � 0.03 mm a -1 .T he Antarctic ice shelves show corresponding mass changes of -95 � 11 Gt a -1 in WA and +142 � 10 Gt a -1 in EA. Thinning at the margins of the Greenland ice sheet and growth at higher elevations is an expected response to increasing temperatures and precipitation in a warming climate. The marked thinnings in the Pine Island and Thwaites Glacier basins of WA and the Totten Glacier basin in EA are probably ice- dynamic responses to long-term climate change and perhaps past removal of their adjacent ice shelves. The ice growth in the southern Antarctic Peninsula and parts of EA may be due to increasing precipitation during the last century.

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