Researchers map geothermal heat flux in West Antarctica; a new potential weak point in the stability of the ice sheet is identified
ALFRED WEGENER INSTITUTE, HELMHOLTZ CENTER FOR POLAR AND MARINE RESEARCH
PICTURE: GEOPHYSICAL MEASUREMENTS WITH A MAGNETOMETER DRAWN WITH THE BOARD HELICOPTER FROM RV POLARSTERN. show more CREDIT: ALFRED-WEGENER-INSTITUT / THOMAS RONGE
Ice loss from the Thwaites Glacier in West Antarctica is currently responsible for around four percent of global sea level rise. That number could rise, as hardly any other ice stream in Antarctica is changing as dramatically as the massive Thwaites Glacier. Until recently, experts attributed these changes to climate change and the fact that the glacier lies on the sea floor in many places and thus comes into contact with warm water masses. But there is also a third one, and so farone of the most difficult influencing factors to limit. German and British researchers have shown in a new study that there is a noticeably large amount of heat from the Earth’s interior under the ice, which has probably influenced the sliding behavior of the ice masses for millions of years. These considerable geothermal heat flows are in turn due to the fact that the glacier lies in a tectonic rift where the earth’s crust is significantly thinner than, for example, in neighboring East Antarctica. The new study was published today in Nature’s online journal Communications Earth & Environment.
In contrast to East Antarctica, West Antarctica is a geologically young region. In addition, it does not consist of a large contiguous land mass, the earth’s crust is up to 40 kilometers thick, but consists of several small and mostly relatively thin crust blocks that pass through. A so-called rift system or rift system are separated from each other. In many of the trenches in this system, the earth’s crust is only 17 to 25 kilometers thick, so much of the soil is one to two kilometers below sea level. On the other hand, the existence of the trenches has long led researchers to assume that a comparatively large amount of heat rose from the earth’s interior 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, the Helmholtz Center for Polar and Marine Research (AWI) and the British Antarctic Survey (BAS) have now provided confirmation.
“Our measurements show that where the earth’s crust is only 17 to 25 kilometers thick, geothermal heat flows of up to 150 milliwatts per square meter can occur under the Thwaites Glacier. This corresponds to values that were measured in areas of the Rhine Graben and the East African Rift Valley, ”says AWI geophysicist and first author of the study, Dr. Ricarda Dziadek.
The geophysicists cannot quantify the extent to which the rising geothermal heat warms the glacier floor based on their data: “The temperature at the bottom of the glacier depends on several factors – for example on whether the soil consists of compact, solid rock or meter-long water-saturated sediments. Water conducts the rising heat very efficiently. But it can also transport thermal energy away before it reaches the glacier floor, ”explains co-author and AWI geophysicist Dr. Karsten Gohl.
Still, the heat flux could be a crucial factor to consider in the future of the Thwaites Glacier. Gohl: “Large amounts of geothermal energy can, for example, prevent the floor of the glacier bed from completely freezing or a permanent film of water forms on its surface. Both would mean that the ice masses slide more easily over the ground. In addition, if the braking effect of the ice shelf is lost, as can currently be observed in West Antarctica, the glacier currents could accelerate significantly due to the increased geothermal energy. “
The new geothermal heat flow maps are based on various geomagnetic. Field data sets from West Antarctica, which the researchers collated and analyzed in an elaborate process. “Inferring geothermal heat flow from magnetic field data is a proven method that is mainly used in regions where little is known about the properties of the geological subsurface,” explains Fausto Ferraccioli of the British Antarctic Survey and the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS), one of the co-authors of the study.
The experts will soon learn how accurate their new estimate of the heat flux below the Thwaites Glacier is. An international team led by British and American polar experts, in which the AWI is also involved, is currently working on a large research project. In this context, the taking of core samples up to the glacier bed and the implementation of corresponding heat flow measurements are planned. The results will provide the first opportunity to fully verify the new West Antarctic heat flow maps.
10.1038 / s43247-021-00242-3
High geothermal heat flux under the Thwaites Glacier in West Antarctica, derived from aeromagnetic data
ITEM RELEASE DATE
17th August 2021