Greenland's ice sheet is currently melting at a rate that is "off the charts" compared with the last 350 years, a new study by scientists from Woods Hole Oceanographic Institution (WHOI) has warned.
According to researchers, Greenland ice melting started in mid-1800s and now contributes to sea level more than at any time during the past three centuries. The findings also clearly demonstrate the impact of climate change on Arctic melting and global sea level rise, according to the research team.
"From a historical perspective, today's melt rates are off the charts, and this study provides the evidence to prove this," said Dr. Sarah Das, a glaciologist at WHOI and co-author of the study.
"We found a 50 per cent increase in total ice sheet meltwater runoff versus the start of the industrial era, and a 30 per cent increase since the 20th century alone."
To determine the rate of Greenland ice melting over the past centuries, the team used a long drill to extract ice cores from the ice sheet in Greenland as well as from an adjacent coastal ice cap. The ice core samples were collected from the sites sitting at altitudes more than 1,830 metres, which allowed them to extend their records back to the 17th century.
At higher elevations, the summer meltwater doesn't run off the ice sheet, but instead refreezes after coming in contact with the snowpack sitting underneath. This frozen meltwater creates distinct ice bands that pile up over years to form layers of densely packed ice.
The core samples collected by the researchers were sent to the ice core labs in the U.S. where scientist determined the age and thickness of the melt layers. Melt layers that were thicker indicated the years in which more melting occurred, whereas thinner sections represented years with less amount of melting.
The team analysed these results in combination with the imaging data collected by various satellites and the data from sophisticated climate models, which enabled them to determine the rate of ice melting, not only at core site, but also broadly across Greenland.
The results suggested that the rapid melting of ice sheet in Greenland in recent decades is remarkable when put into a historical context, and the region is now much more sensitive to warming than it was a few decades ago. Now, even a very small temperature change in the region can cause huge spikes in ice sheet melting, according to the study.
The findings of the study are published in journal Nature.
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