Large rivers form on the surface of Greenland each summer, rapidly moving meltwater from the ice sheet to the ocean. The study provides new evidence of the impacts of climate change on Arctic melting and global sea level rise.
Forecasts for how high and how soon the rise will come vary greatly, partly because scientists lack clarity on how fast warming oceans are melting polar ice sheets.
Greenland's massive ice sheets contain enough water to raise global sea levels by 23 feet, and a new study shows that they are melting at a rate "unprecedented" over centuries - and likely thousands of years.
'And increasing melt began around the same time as we started altering the atmosphere in the mid-1800s'.
Fellow glaciologist and co-author of the report Sarah Das said: "From a historical perspective, today's melt rates are off the charts, and this study provides the evidence to prove this". "We found a fifty percent increase in total ice sheet meltwater runoff versus the start of the industrial era, and a thirty percent increase since the 20th century alone".
A United Nations report in October said that marine ice sheet instability in Antarctica and/or the irreversible loss of the Greenland ice sheet could result in a multi-metre rise in the sea level over hundreds to thousands of years. Icebergs breaking off into the ocean from the edge of glaciers are a spectacular example.
To determine the acceleration of the melt, researchers used a drill the size of a traffic-light pole to extract samples from the ice sheet more than 6,000ft above sea level.
Published today in Nature, the research finds that rates of melting at Greenland's surface have skyrocketed in recent decades and are now far out of bounds of what was considered natural variability over the last few centuries. Rather than increasing steadily as the climate warms, Greenland will melt increasingly more for every degree of warming.
Because of a "nonlinear response of surface melting to increasing summer air temperatures, continued atmospheric warming will lead to rapid increases in [Greenland ice sheet] runoff and sea-level contributions", the study said.
In July 2012, a spate of warm weather caused almost the entire surface of the Greenland ice sheet to begin melting, an event with no precedent in the satellite record.
This study is just the latest indicator that all is not well for the world's second-largest ice sheet. Dark bands running horizontally across the cores, like ticks on a ruler, enabled the scientists to visually chronicle the strength of melting at the surface from year to year.
Global warming is melting ice in Greenland at "unprecedented rates", experts warned. Across the ice sheet, melting was more rapid in 2012 than any other year and the most recent decade included in the ice core-analysis, 2004-2013, experienced "a more sustained and greater magnitude of melt than any other 10-year period" in the 350-year record, the scientists wrote.