East Antarctic melting hotspot identified

Date:
August 24, 2020
Source:
Hokkaido University
Summary:
Ice is melting at a surprisingly fast rate underneath Shirase
Glacier Tongue in East Antarctica due to the continuing influx of
warm seawater into the Lu"tzow-Holm Bay.



FULL STORY ==========================================================================
Ice is melting at a surprisingly fast rate underneath Shirase Glacier
Tongue in East Antarctica due to the continuing influx of warm seawater
into the Lu"tzow- Holm Bay.


========================================================================== Hokkaido University scientists have identified an atypical hotspot of
sub- glacier melting in East Antarctica. Their findings, published in
the journal Nature Communications, could further understandings and
predictions of sea level rise caused by mass loss of ice sheets from
the southernmost continent.

The 58th Japanese Antarctic Research Expedition had a very rare
opportunity to conduct ship-based observations near the tip of East
Antarctic Shirase Glacier when large areas of heavy sea ice broke up,
giving them access to the frozen Lu"tzow-Holm Bay into which the glacier protrudes.

"Our data suggests that the ice directly beneath the Shirase Glacier
Tongue is melting at a rate of 7-16 meters per year," says Assistant
Professor Daisuke Hirano of Hokkaido University's Institute of Low
Temperature Science. "This is equal to or perhaps even surpasses the
melting rate underneath the Totten Ice Shelf, which was thought to be experiencing the highest melting rate in East Antarctica, at a rate
of 10-11 meters per year." The Antarctic ice sheet, most of which is
in East Antarctica, is Earth's largest freshwater reservoir. If it all
melts, it could lead to a 60-meter rise in global sea levels. Current predictions estimate global sea levels will rise one meter by 2100 and
more than 15 meters by 2500. Thus, it is very important for scientists to
have a clear understanding of how Antarctic continental ice is melting,
and to more accurately predict sea level fluctuations.

Most studies of ocean-ice interaction have been conducted on the ice
shelves in West Antarctica. Ice shelves in East Antarctica have received
much less attention, because it has been thought that the water cavities underneath most of them are cold, protecting them from melting.

During the research expedition, Daisuke Hirano and collaborators
collected data on water temperature, salinity and oxygen levels from
31 points in the area between January and February 2017. They combined
this information with data on the area's currents and wind, ice radar measurements, and computer modelling to understand ocean circulation
underneath the Shirase Glacier Tongue at the glacier's inland base.

The scientists' data suggests the melting is occurring as a result of
deep, warm water flowing inwards towards the base of the Shirase Glacier Tongue. The warm water moves along a deep underwater ocean trough and
then flows upwards along the tongue's base, warming and melting the
ice. The warm waters carrying the melted ice then flow outwards, mixing
with the glacial meltwater.

The team found this melting occurs year-round, but is affected by
easterly, alongshore winds that vary seasonally. When the winds diminish
in the summer, the influx of the deep warm water increases, speeding up
the melting rate.

"We plan to incorporate this and future data into our computer models,
which will help us develop more accurate predictions of sea level
fluctuations and climate change," says Daisuke Hirano.


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


========================================================================== Journal Reference:
1. Daisuke Hirano, Takeshi Tamura, Kazuya Kusahara, Kay I. Ohshima,
Keith W.

Nicholls, Shuki Ushio, Daisuke Simizu, Kazuya Ono, Masakazu Fujii,
Yoshifumi Nogi, Shigeru Aoki. Strong ice-ocean interaction beneath
Shirase Glacier Tongue in East Antarctica. Nature Communications,
2020; 11 (1) DOI: 10.1038/s41467-020-17527-4 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200824092000.htm

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