Puzzling Heat from Deep Inside the Earth Is Melting Greenland's Glaciers

Researchers sample the Young Sound, where sea ice acts as a lid on top of the fjord. Data gleaned from this area has allowed researchers to find evidence of yet another source pushing Greenland's ice sheet into the sea. Søren Rysgaard

Scientists already know that the Greenland ice sheet is melting. But the hidden heat source originating from deep inside the Earth partially responsible for that melting has been a mystery. Now, researchers have pinned down evidence of that heat, revealing yet another force pushing glaciers into the ocean.

For more than a decade, researchers have measured temperatures and saltiness in the Young Sound fjord at depths of 650 to 1,100 feet. Fjords are deep, U-shaped valleys connected to the sea and formed by glacial erosion. The region in which the Young Sound fjord is located is filled with hot springs, where water can reach 140 degrees Fahrenheit.

Similar to Iceland, according to the researchers, a significant amount of geothermal activity is bubbling beneath the Earth's surface in Greenland. The heat loss radiating from the geothermal activity of the Earth's interior is melting glaciers from below—making it easier for them to slide into the sea, adding to sea level rise.

"There is no doubt that the heat from the Earth's interior affects the movement of the ice, and we expect that a similar heat seepage takes place below a major part of the ice cap in the northeastern corner of Greenland," Søren Rysgaard, lead author from the bioscience department at Aarhus University said in a statement. The findings published Monday in Scientific Reports, by researchers also at Arctic Research Centre and the Greenland Institute of Natural Resources, will help to improve predictions of sea level rise as well as the stability of the Greenland ice sheet.

Heat loss from the Earth's interior is warming the deep depths of water in the Young Sound fjord in northeast Greenland. Wieter Boone

The combination of rising temperatures in the air and sea, precipitation from above, particular dynamics of the ice sheet and now heat loss from the Earth's interior is causing the Greenland ice sheet to lose its mass, according to Rysgaard. The Earth's interior heat loss causes deep sea temperatures in the fjords to warm up, which results in yet another source of glacial melting.

This source of heat—scientifically known as the geothermal heat flux—is found all over the planet and dates back to Earth's formation, according to co-author, Jørgen Bendtsen, of Aarhus University. Geothermal heat fluxes are difficult to measure and aren't distributed evenly across the planet, so "our results are very unique because we determine the relatively small heat flux from a decade-long warming of an almost stagnant water mass," Bendtsen told Newsweek by email.

The warming and melting from below the ice sheets caused by these heat fluxes "lubricates the interface between the ice and the ground resulting in a much faster ice flow," Bendtsen said. The speed of the ice flow—meaning, how quickly glaciers slide into the sea—can increase from this warmth beneath them.

Several glaciers flow into the area of Young Sound where researchers have shown that heat from the Earth's interior warms up the bottom water of the fjord. Mikael Sejr

The findings from the latest study can inform future predictions of ice flow from Greenland's ice sheet. Understanding these unique processes in which polar ice is melting will help to pinpoint how soon and by exactly how much global sea levels will rise.