Geophys. Res. Lett. 34, L22507 (2007)

Credit: NASA

Summertime melting of the Greenland ice sheet has been increasing over the last 34 years and was most extreme in 2007, finds new research.

Thomas Mote from the University of Georgia in the US monitored melting of the Greenland ice sheet from 1973 until 2007 by detecting changes in microwave radiation measured by satellites. Comparing the extent of melt to seasonal averages, he found that melting during June, July and August significantly increased over the past 34 years. This trend was related to increasing air temperatures observed at three coastal Greenland stations. But in 2007 there was 60% greater melting than in 1998, the previous highest-melt year — more than expected from the temperature trend alone. This may be the accumulated effect of increased melting over the prior four years, because, for instance, more heat is absorbed by the Earth's surface when it is snow-free.

This latest study is an important step towards understanding how rapidly the Greenland ice sheet is vanishing, which has important implications for global sea-level rise.