Fire in the Hole

If you want to cook something quickly, you heat it from both sides. This is the genius of the toaster. That’s what’s happening to the West Antarctic ice sheet—with alarming consequences. A new study published today in the journal Science Advances reveals that the area beneath the ice sheet is far hotter than previously thought, fed by an unexpected flow of geothermal energy. While our carbon emissions heat the atmosphere above the continent, earth is melting its ice from below. Think of it as the world’s largest panini press.

Here’s the background. Radioactive isotopes in the core of the earth are constantly decaying, which emits a massive amount of energy. That energy moves from the core to the crust, dissipating as it goes. For this reason, if you were to drill deep at a random location on the continents, you would find that the temperature in your hole increases about 25 degrees Celsius for every kilometer you descend, on average. Scientists call this the geothermal gradient.

The geothermal gradient, however, isn’t constant. Our planet’s mantle and crust aren’t uniform, so heat is conducted at different rates in different places. There are also unique upwellings of heat in certain areas. The Hawaiian Islands are the result of such an upwelling—heat surging from deep within the earth melted the crystals in the mantle, and the resulting lava was ejected to the surface to form the volcanic islands.

Until recently, no one had drilled deeply enough through the West Antarctic ice—which is 6,500 feet thick in places—to determine the geothermal gradient underneath. For the new study, researchers from three U.S.-based institutions drilled all the way through the ice and into the mud. They calculated a geothermal gradient of approximately 200 degrees Celsius per kilometer, which is several times the global average on continents.

Few predicted this result, although there have been indications that the earth below the West Antarctic ice is unusually hot. The ice sheet flows more quickly than similar ice formations, lubricated by a layer of melted ice between ground and ice sheet. There are also many lakes beneath the ice, some warm enough to host vibrant microbial ecosystems. That heat had to come from somewhere.

Even with the new discovery, though, we still don’t know exactly where the heat is coming from. One interesting possibility is volcanoes, which are hidden beneath the ice. As recently as 2013, scientists were still discovering subglacial volcanoes in the area, and there may be many more.

Climate deniers claim these volcanoes, rather than manmade climate change, are responsible for melting the region’s ice, but this is just one of their many, many faulty interpretations of data. While it’s true that heat coming from within the earth, including heat associated with volcanoes, accelerates the melting, it is just one contributor to the loss of the West Antarctic ice sheet—and not the primary culprit. Today’s study could help us understand how the entire system, including global warming, is melting the ice.

“It is important that we get this number right if we are going to make accurate predictions of how the West Antarctic ice sheet will behave in the future, how much it is melting, how quickly ice streams flow, and what the impact might be on sea level rise,” says Slawek Tulaczyk, a glaciologist at the University of California, Santa Cruz and one of the study leaders.

Even better, we need to find a way to turn off the heat from above. Ice paninis aren’t such a great idea.