Glacial Earthquakes Help Scientists Track Massive Ice Loss in Greenland

Glacial quakes may actually help researchers track massive ice loss. Researchers have examined the quakes more closely and have that that they occur when the glacier moves rapidly backward and downward after an iceberg breaks off into the ocean.

Until now, glacial earthquakes have been poorly understood. Because the Greenland ice sheet is an important contributor to global sea level rise, it's crucial to better understand its behavior.

Glacial quakes have increased sevenfold in the last two decades. In addition, these quakes have been migrating north, which suggests that there's been an increase in rates of mass loss from the ice sheet through calving.

"Our new understanding is a crucial step toward developing tools to remotely measure the mass loss that occurs when icebergs break off ice sheets," said L. Mac Cathles, co-author of the new study, in a news release. "Combining field observations with laboratory measurements from scaled-model calving experiments provided insights into the dynamics of calving and glacial earthquakes that would not have otherwise been possibile."

During the summer of 2013, the researchers installed a wireless network of Global Positioning System devices on the chaotic surface of Helheim Glacier to measure velocity and displacement glacier surface. This glacier is one of the largest in southeast Greenland.

"We were really surprised to see the glacier flowing backward in our GPS data," said Tavi Murray, the lead author of the new study. "The motion happens every time a large iceberg is calved and a glacial earthquake is produced. A theoretical model for the earthquake and the laboratory experiments has allowed us to explain the backward and downward movement."

The findings reveal a bit more about glacial behavior. This is a crucial step toward measuring calving events and their contribution to sea-level change, which may give researchers better estimates in the future.

The findings are published in the journal Science.

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