Greenland Ice Sheet
February 7, 2014

Ocean Warming Causes Greenland Ice Sheet Loss

Lee Rannals for - Your Universe Online

Researchers writing in the journal Nature say that ocean warming could be causing a four-fold increase in ice loss on the Greenland Ice Sheet.

The Greenland Ice Sheet is about a 2-mile thick layer of ice that covers the country. Glaciers that drain the ice sheet plunge into coastal fjords that are about 2,000 feet deep, helping to expose the ice sheet edges that contact the ocean. Oceanographers from Woods Hole Oceanographic Institution (WHOI) and MIT say one trigger for the speed up and retreat of these glaciers that contributed to this ice loss is ocean warming.

“What a lot of research around Greenland and the fjords has shown is that if the North Atlantic Ocean warms, then these warm waters will rapidly reach the fjords and hence the margins of Greenland’s glaciers,” said Fiamma Straneo of WHOI.

It is now important to understand if the present ocean warming has contributed to ice loss, and whether or not future warming could result in even more loss. The researchers have determined the mechanisms driving the melting of the ice sheet, finding that “submarine melting” has increased as the ocean and atmosphere have warmed over the past few decades.

A warmer atmosphere has caused an increase in surface melting above the ice sheet, and this runoff is enhancing the submarine melting. According to the study, surface melt water falls through cracks in the glacier to create a freshwater river that rushes out into the ocean at the base of the glacier. This river mixes up with the seawater, contributing to the heat transfer from the ocean to the ice, which results in even more submarine melting beneath the sea surface.

“If you put an ice cube in a glass of water and don’t touch it, it will take a few minutes to melt. But if you stir it, you are making it easier for the warmer water to reach the ice surface, which makes the ice melt faster,” Straneo explains.

She said that the warming ocean and atmosphere is like a double hit on the submarine melting.

“It increases because the ocean is warming, but also because there’s increased surface melt that flows to the ice-ocean boundary and increases submarine melting even more,” Straneo added.

While Straneo and colleagues have made great strides in understanding the ice loss process in Greenland, the team still lacks some instruments to help make these measurements more defined.

“Part of what we struggled with, in understanding how the ocean can affect the glaciers, was there were hardly any measurements of ocean conditions near the glaciers before everything started changing,” says Straneo. “We have very few measurements where the ice and the ocean meet. Autonomous vehicles might help some and so may moorings deployed through the ice. It’s just that they are expensive and funding is limited.”

She said it is important to find more resources and technology to help build up the record of data, so scientists can have an even better understanding of this ice loss.

“If we don’t start collecting these measurements for longer periods of time, we’re leaving the same questions that we’re struggling with today for the next generation to answer,” said Straneo.