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Geothermal heat found under Thwaites Glacier

Written by Oceanographic staff

Researchers found significant geothermal heat beneath the Thwaites Glacier in West Antarctica – an ice stream that is responsible for four per cent of global sea-level rise.

A new study by German and British researchers, published in the Nature online journal Communications Earth & Environment, has revealed a large amount of heat from the earth’s interior beneath the ice, which has likely affected the sliding behaviour of the ice masses for millions of years.

Ice losses from Thwaites Glacier in West Antarctica are currently responsible for roughly four per cent of the global sea-level rise. And this figure could increase as no other ice stream in the Antarctic changes as quickly as the Thwaites Glacier, also often referred to as the ‘Doomsday Glacier‘.

The research vessel Polarstern near an iceberg in Pine Island Bay. (Photo: Thomas Ronge)

Until recently, experts attributed these ice losses to climate change and the fact that the glacier comes into contact with warm water as it rests on the seafloor. But there is also a third, and until now, one of the most difficult to constrain, influencing factors: geothermal heat flow.

AWI geophysicist and first author of the study, Dr Ricarda Dziadek, says: “Our measurements show that where the Earth’s crust is only 17 to 25 kilometres thick, a geothermal heat flow of up to 150 milliwatts per square metre can occur beneath Thwaites Glacier. This corresponds to values recorded in areas of the Rhine Graben and the East African Rift Valley.”

Unlike East Antarctica, West Antarctica is a geologically young region. In addition, it doesn’t consist of a large contiguous land mass, where the Earth’s crust is up to 40 kilometres thick, but instead is made up of several small and for the most part relatively thin crustal blocks that are separated from each other by a so-called trench system or rift system.

In many of the trenches in this system, the Earth’s crust is only 17 to 25 kilometres thick, and as a result a large portion of the ground lies one to two kilometres below sea level. On the other hand, the existence of the trenches has long led researchers to assume that comparatively large amounts of heat from Earth’s interior rose to the surface in this region. With their new map of this geothermal heat flow in the hinterland of the West Antarctic Amundsen Sea, experts from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) and the British Antarctic Survey (BAS) have now provided confirmation.

Based on their data, the geophysicists are unable to put a figure on the extent to which the rising geothermal heat warms the bottom of the glacier: “The temperature on the underside of the glacier is dependent on a number of factors – for example whether the ground consists of compact, solid rock, or of metres of water-saturated sediment. Water conducts the rising heat very efficiently. But it can also transport heat energy away before it can reach the bottom of the glacier,” explains co-author and AWI geophysicist Dr Karsten Gohl.

Nevertheless, the heat flow could be a crucial factor that needs to be considered when it comes to the future of Thwaites Glacier. An international team of British and American polar experts is currently collecting core samples from the glacier bed and taking heat flow measurements to find out exactly how accurate the new assessments are. The findings will provide the first opportunity to comprehensively verify the new heat flow maps from West Antarctica.

For information regarding co-authors and to read the full study, ‘High geothermal heat flow beneath Thwaites Glacier in West Antarctica inferred from aeromagnetic data’, click here

For more from our Ocean Newsroom, click here.

Photography courtesy of Thomas Ronge.

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