A team led by Kaitlin Keegan of Dartmouth College in New Hampshire analysed six shallow ice cores from the dry snow region in central Greenland. They found that before the widespread melt of 2012, the most recent such event took place in 1889.
One of the cores, taken from the centre of the ice sheet, showed that in both 1889 and 2012, black carbon from Northern Hemisphere forest fires caused the albedo – the ability to reflect sunlight – of the ice cap to drop below a critical threshold. Both years were also characterised by exceptionally warm temperatures, and the combination of factors caused the large-scale melting events.
‘The widespread melting of the Greenland ice sheet required the combination of both of these effects – a lowered snow albedo from ash and unusually warm temperatures – to push the ice sheet over the threshold,’ Keegan said. ‘With both the frequency of forest fires and warmer temperatures predicted to increase with climate change, widespread melt events are likely to happen much more frequently in the future.’
This story was published in the July 2014 edition of Geographical Magazine
