Thwaites glacier: Significant geothermal heat beneath the ice stream
Researchers map the geothermal heat flow in West Antarctica; a new
potential weak spot in the ice sheet's stability is identified

Date:
August 18, 2021
Source:
Alfred Wegener Institute, Helmholtz Centre for Polar and Marine
Research
Summary:
Ice losses from Thwaites Glacier in West Antarctica are currently
responsible for roughly four percent of the global sea-level
rise. This figure could increase, since virtually no another ice
stream in the Antarctic is changing as dramatically as the massive
Thwaites Glacier.

Until recently, experts attributed these changes to climate change
and the fact that the glacier rests on the seafloor in many places,
and as such comes into contact with warm water masses. But there is
also a third, and until nowone of the most difficult to constrain,
influencing factors. In a new study, German and British researchers
have shown that there is a conspicuously large amount of heat from
Earth's interior beneath the ice, which has likely affected the
sliding behavior of the ice masses for millions of years. This
substantial geothermal heat flow, in turn, are due to the fact
that the glacier lies in a tectonic trench, where the Earth's
crust is significantly thinner than it is e.g. in neighboring
East Antarctica.



FULL STORY ==========================================================================
Ice losses from Thwaites Glacier in West Antarctica are currently
responsible for roughly four percent of the global sea-level rise. This
figure could increase, since virtually no another ice stream in
the Antarctic is changing as dramatically as the massive Thwaites
Glacier. Until recently, experts attributed these changes to climate
change and the fact that the glacier rests on the seafloor in many places,
and as such comes into contact with warm water masses. But there is also
a third, and until nowone of the most difficult to constrain, influencing factors. In a new study, German and British researchers have shown that
there is a conspicuously large amount of heat from Earth's interior
beneath the ice, which has likely affected the sliding behaviour of the
ice masses for millions of years. This substantial geothermal heat flow,
in turn, are due to the fact that the glacier lies in a tectonic trench,
where the Earth's crust is significantly thinner than it is e.g. in neighbouring East Antarctica. The new study was published today in the
Nature online journal Communications Earth & Environment.


========================================================================== 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.

"Our measurements show that where the Earth's crust is only 17 to 25
kilometres thick, 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,"
says AWI geophysicist and first author of the study, Dr Ricarda Dziadek.

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. According
to Gohl: "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. If, in
addition, the braking effect of the ice shelf is lost, as can currently
be observed in West Antarctica, the glaciers' flow could accelerate considerably due to the increased geothermal heat." The new geothermal
heat flow maps are based on various geomagnetic. field datasets from
West Antarctica, which the researchers have collated and analysed using
a complex procedure. "Inferring geothermal heat flow from magnetic field
data is a tried and tested method, mainly used in regions where little
is known about the characteristics of the geological underground,"
explains Fausto Ferraccioli from the British Antarctic Survey and the
Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS),
one of the study's co-authors.

The experts will soon find out how accurate their new assessment of
the heat flow below Thwaites Glacier is. An international team led by
British and American polar experts, which the AWI is also taking part
in, is currently engaged in a major research project. In this context, collecting core samples down as far as the glacier bed and taking
corresponding heat flow measurements are planned. The findings will
provide the first opportunity to comprehensively verify the new heat
flow maps from West Antarctica.

========================================================================== Story Source: Materials provided by Alfred_Wegener_Institute,_Helmholtz_Centre_for_Polar_and
Marine_Research. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Ricarda Dziadek, Fausto Ferraccioli, Karsten Gohl. High geothermal
heat
flow beneath Thwaites Glacier in West Antarctica inferred from
aeromagnetic data. Communications Earth & Environment, 2021; 2
(1) DOI: 10.1038/s43247-021-00242-3 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210818083957.htm

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