In Greenland, extreme melting has reduced ice sheet storage in arctic polar regions: Study

Having experienced five record-breaking ‘extreme melting’ seasons since 2000, the Greenland Ice Sheet has lost its ice storage capacity across 98.6 percent of the cold polar areas at high altitudes. This has also increased the likelihood of future melt-raising sea levels, a new study conducted by a team of researchers in the US on Tuesday has revealed. The record melt of Greenland's ice sheet caused by unusually high temperatures was first detected in 2012, as scientists accumulated the melting maps and data from three different satellite sensors, including the Oceansat‐2 scatterometer, the Moderate‐resolution Imaging Spectroradiometer, and the Special Sensor Microwave Imager. 

“Satellite observations reveal that melt occurred at or near the surface of the Greenland ice sheet to its entire extent on 12 July 2012. This melt event coincided with an anomalous ridge of warm air that became stagnant over Greenland,” scientists explained.

“Such a melt event is rare with the last significant one occurring in 1889 and the next previous one around seven centuries earlier in the Medieval Warm Period,” they further added. 

In the study published by Stanford University in Nature Communications on April 20, researchers deciphered a trove of data and found that the melting of the Greenland ice sheet (GIS) was also one of the planet’s key contributors to sea-level rise. It was found from the ice-penetrating radar data that the melting left behind a contiguous layer of refrozen ice inside the snowpack, including near the middle of the ice sheet where surface melting is usually minimal. This caused a change in the ice sheet’s behaviour by reducing its ability to store future meltwater. 

“When you have these extreme, one-off melt years, it’s not just adding more to Greenland’s contribution to sea-level rise in that year – it’s also creating these persistent structural changes in the ice sheet itself,” said lead study author Riley Culberg, a PhD student in electrical engineering. “This continental-scale picture helps us understand what kind of melt and snow conditions allowed this layer to form,” he continued. 

What caused the melting, ice shifting scenario?

Warm temperatures exacerbated by high atmospheric pressure since 2012 due to climate change has caused this extreme melting event. Researchers used the airborne radar data to detect a major expansion to single-site field observations on the icy poles. Furthermore, through advanced modeling, the team was able to re-analyze radar data collected by flights from NASA’s Operation IceBridge from 2012 to 2017 to interpret melt near the surface of the ice sheet, at a depth up to about 50 feet. “Once those challenges were overcome, all of a sudden, we started seeing meltwater ice layers near the surface of the ice sheet,” Schroeder said. “It turns out we’ve been building records that, as a community, we didn’t fully realize we were making.”

According to scientists, melting ice sheets will drastically raise sea levels.  Ice sheet regions that haven’t experienced extreme melt can store meltwater in the upper 150 feet, preventing it from flowing into the ocean. But a melt layer like the one from 2012 can reduce the storage capacity to about 15 feet in some parts of the Greenland Ice Sheet. This also causes structural changes, which implies that the way the ice sheet responds to surface melting is also going to be impacted in the longer term, Culberg said.