Greenland ice loss rates 'one-third' of what was thought
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The rate at which ice is disappearing from Greenland and Western Antarctica has been seriously overestimated, according to new research.
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Thus it is that since 2002, NASA's Gravity Recovery and Climate Experiment (GRACE) satellite data has been used to make an estimate of ice melt from Greenland and Western Antarctica. (The rest of Antarctica doesn't seem to be melting at all - indeed Antarctica as a whole is actually gaining ice area rather than losing it - but some regions in the West are melting. The reasons for this are under investigation.)
The original GRACE-based estimates indicated as much as 1,500 billion tonnes ice loss just from Greenland in the period 2003-2009 - equivalent to a global sea-level rise of over 4mm on its own. However it has since become clear that these numbers weren't properly corrected for the phenomenon of "rebound", where the Earth's crust rises as ice is removed. GPS precise-location devices fixed to bedrock outcrops in Antarctica showed this last year, but nobody was sure how bad the errors were.
Now a team of researchers based at NASA's Jet Propulsion Laboratory and in the Netherlands say they have the answer.
Vermeersen and his colleagues' calculations show that as little as 500 gigatonnes of ice or even less could have melted from Greenland during 2003-2009, translating into less than 2mm of sea-level rise. In the case of Greenland, it could be that the current estimates are triple what they should be.