Unsettling currents: Warm water flowing beneath the 'Doomsday Glacier'
Data from underneath Thwaites Glacier, also known as the Doomsday Glacier


Date:
April 9, 2021
Source:
University of Gothenburg
Summary:
Researchers have been able to obtain data from underneath Thwaites
Glacier, also known as the 'Doomsday Glacier'. They find that
the supply of warm water to the glacier is larger than previously
thought, triggering concerns of faster melting and accelerating
ice flow.



FULL STORY ==========================================================================
For the first time, researchers have been able to obtain data from
underneath Thwaites Glacier, also known as the "Doomsday Glacier." They
find that the supply of warm water to the glacier is larger than
previously thought, triggering concerns of faster melting and accelerating
ice flow.


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With the help of the uncrewed submarine Ran that made its way under
Thwaites glacier front, the researchers have made a number of new
discoveries. Professor Karen Heywood of the University of East Anglia commented: "This was Ran's first venture to polar regions and her
exploration of the waters under the ice shelf was much more successful
than we had dared to hope.

We plan to build on these exciting findings with further missions under
the ice next year." The submersible has, among other things, measured
the strength, temperature, salinity and oxygen content of the ocean
currents that go under the glacier.

Global sea level is affected by how much ice there is on land, and the
biggest uncertainty in the forecasts is the future evolution of the West Antarctic Ice Sheet, says Anna Waahlin, professor of oceanography at the University of Gothenburg and lead author of the new study now published
in Science Advances.

Impacts global sea level The ice sheet in West Antarctica accounts for
about ten percent of the current rate of sea level rise; but also the
ice in West Antarctica holds the most potential for increasing that rate because the fastest changes worldwide are taking place in the Thwaites
Glacier. Due to its location and shape, Thwaites is particularly sensitive
to warm and salty ocean currents that are finding their way underneath it.



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This process can lead to an accelerated melting taking place at the
bottom of the glacier and inland movement of the so-called grounding
zone, the area where the ice transitions from resting on the seabed to
floating in the ocean.

Due to its inaccessible location, far from research stations, in an area
that is usually blocked by thick sea ice and many icebergs, there has
been a great shortage of in situ measurements from this area. This means
that there are big knowledge gaps for the ice-ocean boundary processes
in this region.

First measurements performed In the study, the researchers present the
results from the submersible that measured strength, temperature, salinity
and oxygen content of the ocean currents that go under the glacier.

"These were the first measurements ever performed beneath Thwaites
glacier," says Anna Waahlin.



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The results have been used to map the ocean currents underneath the
floating part of the glacier. The researchers discovered that there is
a deep connection to the east through which deep water flows from Pine
Island Bay, a connection that was previously thought to be blocked by
an underwater ridge.

The research group has also measured the heat transport in one of the
three channels that lead warm water towards Thwaites Glacier from the
north. "The channels for warm water to access and attack Thwaites weren't
known to us before the research. Using sonars on the ship, nested with
very high-resolution ocean mapping from Ran, we were able to find that
there are distinct paths that water takes in and out of the ice shelf
cavity, influenced by the geometry of the ocean floor" says Dr Alastair
Graham, University of Southern Florida.

The value measured there, 0.8 TW, corresponds to a net melting of 75 km3
of ice per year, which is almost as large as the total basal melt in the
entire ice shelf. Although the amount of ice that melts as a result of
the hot water is not much compared to other global freshwater sources,
the heat transport has a large effect locally and may indicate that the
glacier is not stable over time.

Not sustainable over time The researchers also noted that large amounts
of meltwater flowed north away from the front of the glacier.

Variations in salinity, temperature and oxygen content indicate that
the area under the glacier is a previously unknown active area where
different water masses meet and mix with each other, which is important
for understanding the melting processes at the base of the ice.

The observations show warm water approaching from all sides on pinning
points, critical locations where the ice is connected to the seabed and
give stability to the ice shelf. Melting around these pinning points
may lead to instability and retreat of the ice shelf and, subsequently,
the upstream glacier flowing off the land. Dr Rob Larter of the British Antarctic Survey commented: "This work highlights that how and where
warm water impacts Thwaites Glacier is influenced by the shape of the
sea floor and the ice-shelf base as well as the properties of the water
itself. The successful integration of new sea-floor survey data and observations of water properties from the Ran missions shows the benefits
of the multidisciplinary ethos within the International Thwaites Glacier Collaboration." "The good news is that we are now, for the first time, collecting data that is necessary to model the dynamics of Thwaite's
glacier. This data will help us better calculate ice melting in the
future. With the help of new technology, we can improve the models and
reduce the great uncertainty that now prevails around global sea level variations." says Anna Waahlin.

========================================================================== Story Source: Materials provided by University_of_Gothenburg. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. A. K. Waahlin, A. G. C. Graham, K. A. Hogan, B. Y. Queste,
L. Boehme, R.

D Larter, E. C. Pettit, J. Wellner and K. J. Heywood. Pathways
and modification of warm water flowing beneath Thwaites Ice Shelf,
West Antarctica. Science Advances, 2021 DOI: 10.1126/sciadv.abd7254 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/04/210409145854.htm

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