During Greenland’s hottest summers on record, 2010 and 2012, the ice in Rink Glacier on the island’s west coast slid through the glacier’s interior in a gigantic wave. According to a new NASA study, it was “like a warmed freezer pop sliding out of its plastic casing.”
The wave persisted for four months, with ice from upstream continuing to move down to replace the missing mass for another four months, the study said.
This was the first research study to precisely track a glacier’s loss of mass from melting ice using the horizontal motion of a GPS sensor.
The wave could not have been detected by the usual methods of monitoring Greenland’s ice loss, such as measuring the thinning of glaciers with airborne radar, NASA said.
“You could literally be standing there and you would not see any indication of the wave,” said Eric Larour, a coauthor of the study. “You would not see cracks or other unique surface features.”
The long pulse of mass loss, called a solitary wave, is a new discovery that may increase the potential for sustained ice loss in Greenland as the climate continues to warm, with implications for the future rate of sea level rise, the study said.
During the two summers when solitary waves occurred, the surface snowpack and ice of the huge basin in Greenland’s interior behind Rink Glacier held more water than ever before. In 2012, more than 95 percent of the surface snow and ice was melting, NASA said.
Meltwater may create temporary lakes and rivers that quickly drain through the ice and flow to the ocean. Once the water had formed pathways to the base of the glacier, the wave of intense loss began.
Researchers did not quantify the exact size and speed of the 2010 wave, but the patterns of motion in the GPS data indicate that it must have been smaller than the 2012 wave but similar in speed.
“We know for sure that the triggering mechanism was the surface melting of snow and ice, but we do not fully understand the complex array of processes that generate solitary waves,” said Surendra Adhikari, leader of the study.
Previously known processes combined to make the mass move so quickly, scientists theorize. The huge volume of water lubricated the base of the glacier, allowing it to move more rapidly, and softened the side margins where the flowing glacier meets rock or stationary ice.
The changes allowed the ice to slide downstream so fast that ice farther inland couldn’t keep up.
“Intense melting such as we saw in 2010 and 2012 is without precedent, but it represents the kind of behavior that we might expect in the future in a warming climate,” added coauthor Erik Ivins. “We’re seeing an evolving system.”