An unusually hot melting season in 2010 accelerated ice loss in southern Greenland by 100 billion tonnes, according to new findings by American researchers, indicating the impact of climate change. Large portions of the island’s bedrock also rose an additional quarter of an inch in response to the heat, according to data collected from a network of nearly 50 GPS stations planted along the Greenland coast to measure the bedrock’s natural response to the ever-diminishing weight of ice above it.
Every year as the Greenland Ice Sheet melts, the rocky coast rises, explained Michael Bevis, Ohio eminent scholar in geodynamics and Professor in the School of Earth Sciences at Ohio State University.
Some GPS stations around Greenland routinely detect uplift of 15 mm or more, year after year. But a temperature spike in 2010 lifted the bedrock a detectably higher amount over a short five-month period — as high as 20 mm in some locations.
In a presentation at the American Geophysical Union meeting in San Francisco, Bevis described the study’s implications for climate change.
“Pulses of extra melting and uplift imply that we’ll experience pulses of extra sea level rise,” he said. “The process is not really a steady process,” Bevis, also the principal investigator for the Greenland GPS Network (GNET), said.
Because the solid earth is elastic, Bevis and his team can use the natural flexure of the Greenland bedrock to measure the weight of the ice sheet, just like the compression of a spring in a bathroom scale measures the weight of the person standing on it.
Bevis is confident that the anomalous 2010 uplift that GNET detected is due to anomalous ice loss during 2010.
“Really, there is no other explanation. The uplift anomaly correlates with maps of the 2010 melting day anomaly. In locations where there were many extra days of melting in 2010, the uplift anomaly is highest,” he said.
In 2010, the southern half of Greenland lost an extra 100 billion tons of ice under conditions that scientists would consider anomalously warm.
Southern Greenland stations that were very close to zones of heavy ice loss rose as much as 20 mm over the five months.
Even stations that were located far away typically rose at least 5 mm during the course of the 2010 melting season. But stations in the North of Greenland barely moved at all.
