How the Ocean Causes Greenland Ice Sheet Melt: Rapid Currents and Warmer Waters

The Greenland Ice Sheet has continued to melt over the past several years. Now, scientists are taking a closer look at this melting and learning what role the ocean plays in it.

In the last 40 years, ice loss from the massive Greenland Ice Sheet has increased four-fold, contributing to about one-quarter of global sea level rise. While some of the increased melting is due to the warmer atmosphere, the ocean also plays a role. That's why scientists decided to take a closer look.

"Scientists have noticed a link between glacier behavior and warming waters off the coast of Greenland, but we have very few direct measurements of ocean waters near the glaciers or at what time scales they vary, which are needed to understand what's happening there," said Rebecca Jackson, one of the researchers, in a news release.

In order to learn a bit more about the mechanisms causing the ice to melt, the scientists needed more data. They deployed multiple moorings in two fjords where the third and fifth largest outlet glaciers of the Greenland Ice Sheet end. This allowed them to get a better glimpse as to what exactly was happening between the ice and the ocean.

So what did they find? The researchers discovered rapid fluctuations in ocean temperature near the glaciers, resulting from surprisingly fast ocean currents in the fjords. These currents reversed every few days and were driven by winds and ocean currents outside the fjord. This seemed to imply that changes in temperature in the ocean waters outside the fjord can rapidly impact the glacier through an efficient water pumping mechanism.

"We see more variability in the upper fjord than we would have expected," said Jackson. "Our findings go against the prevailing paradigm that focused on the input of freshwater to the fjord as a driver of new water into the fjord. These observations of ocean conditions near outlet glaciers are one step towards a better understanding of submarine melting and the impact of the ocean on the Greenland Ice Sheet."

The findings are published in the journal Nature Geoscience.