This story is about ice loss, but it’s not actually due to climate change. That’s different.

The Thwaites Glacier in West Antarctica has been responsible for about four percent of the sea-level rise we are experiencing around the world today. That’s a lot for one relatively small piece of ice, and it’s expected to go up as a percentage because no other Antarctic ice stream is experiencing the same level of mass loss. Most researchers attributed all this ice loss to climate change with a bit of contribution due to the glacier coming in contact with warmer water sources naturally.

Now, in a new study published in Nature Communications Earth & Environment, scientists have been able to confirm another factor in the ice loss — geothermal heat flow. It turns out that the glacier is in a tectonic trench. We’ve talked about those before on the show. They’re generally due to one tectonic plate plunging or subducting under another. And where there is a trench, the crust is relatively thin – only about 17 to 25 kilometers thick compared to the continental crust that is up to 40 kilometers thick. That’s a significant difference. And that difference provides a pathway for more of that radiative geothermal heat to get closer to the surface and melt ice.

As heat tends to do.

Lead author Dr. Ricarda Dziadek explains: Our measurements show that where the Earth’s crust is only 17 to 25 kilometers thick, geothermal heat flow of up to 150 milliwatts per square meter can occur beneath Thwaites Glacier. This corresponds to values recorded in areas of the Rhine Graben and the East African Rift Valley.

Note: The East African Rift Valley is full of volcanoes because the crust is so thin that the mantle is welling up basically everywhere. So that’s fun.

Co-author Dr. Karsten Gohl also explains: Large amounts of geothermal heat can, for example, lead to the bottom of the glacier bed no longer freezing completely or to a constant film of water forming on its surface. Both of which would result in the ice masses sliding more easily over the ground.

Not much we can do about ice loss due to geothermal heat except try to understand it further. To that end, an international team is going to collect core samples from the glacier and measure the heat flow in situ. We’ll bring you those results once they are published.

More Information

Alfred Wegener Institute press release

“High geothermal heat flow beneath Thwaites Glacier in West Antarctica inferred from aeromagnetic data,” Ricarda Dziadek, Fausto Ferraccioli and Karsten Gohl, 2021 August 18, Communications Earth & Environment