A continuous, multi-century analysis of the melt intensity and runoff of the Greenland Ice Sheet is reported in a paper published this week in Nature. The findings reveal that the Greenland Ice Sheet has melted at a faster rate recently than in the past.

The Greenland Ice Sheet is a major contributor to modern sea-level rise. However, it is unknown whether the current melting rates are unusual, as observational records do not date far back enough, and previous research did not analyse the entire ice sheet.

Luke Trusel and colleagues developed a record that spans over 350 years by analysing melt layers in ice cores from western Greenland. The authors linked these layers to broader melt processes across Greenland in the modern era. Using this relationship, they extend the Greenland-wide record back to 1650, and report that melt and runoff from the Greenland Ice Sheet have recently accelerated outside the range of past variability.

The authors find that Greenland Ice Sheet melting began to increase soon after the onset of industrial-era Arctic warming in the mid-1800s. Additionally, surface melting in 2012 was more extensive than in any time over the past 350 years, and the most recent decade contained in the ice cores (2004-2013) experienced more sustained and intense melting than any other 10-year period recorded. The analysis shows that melt increases nonlinearly with rising temperatures. Consequently, although a past minor warming event might have had little or no impact on melt, the same event in a future, warmer climate could produce a substantially larger melt event.