Greenland's glaciers likely melting faster than thought

Store Glacier
New maps created by UCI and JPL show that the seafloor under Store Glacier is 1,500 feet (500 meters) deeper than previously thought.

A team of researchers from UC-Irvine and Nasa's Jet Propulsion Laboratory went about mapping the sea floor of Greenland's fjords and the topography they found is conducive to warmer waters — which means more rapid melting, and potentially, a greater rise in sea levels around the world.

The study came out of a gap in researchers' understanding of Greenland's fjords, which are long, narrow inlets of water created by glacial erosion. These bodies of water are often where ocean meets ice, making them a crucial part of glacial melting.

Previous seafloor maps of Greenland were based on very little data, said the study's lead author Eric Rignot, professor of Earth system science at UCI and a JPL researcher.

"So we tend to underestimate how deep these fjords are," he explained.

Rignot's team used underwater scanning equipment to map the fjords.

It took them several years and several expeditions to map an area roughly the size of Rhode Island. When they were done, they found many of the fjords were much deeper than previously estimated.

That's bad news for the glaciers there because in that part of the world, deeper waters tend to be much warmer than shallow waters. In more tropical areas warmer waters are closer to the ocean's surface.

Typical Greenland glacier
The diagram represents a typical glacier in Greenland. Below the cold, fresh layer near the surface a layer of warm, salty water reaches into the fjords to melt the glacier's edge.

So, the deeper the fjords, the more the glaciers there are exposed to warmer water, leading to faster melting and increased sea level rise around the world, Rignot explained, particularly in places like California.

"In fact the irony of melting ice in the polar regions is that it increases sea level faster when you are far away from the ice sheets than when you are close to them," he said.

Rignot said as ice melts in polar regions, it take weight off the Earth's crust, allowing the land there to rise up ever so slightly, keeping sea levels at bay. It's part of a phenomenon known as "sea level fingerprints."

So as ice melts in Greenland, for example, the crust there may rise blocking water from coming on shore, but instead that extra ocean could make floods more likely in California.

Armed with these new maps, Rignot and his team hope to help researchers make better predictions about the rate of glacial melting in Greenland and the subsequent sea level rise around the world.

They also hope to keep mapping that region to improve our understanding of its water, ice and land.

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