Deep channels link ocean to Antarctic glacier

Date:
September 8, 2020
Source:
British Antarctic Survey
Summary:
Newly discovered deep seabed channels beneath Thwaites Glacier
in West Antarctica may be the pathway for warm ocean water to
melt the underside of the ice. Data from two research missions,
using aircraft and ship, are helping scientists to understand the
contribution this huge and remote glacier is likely to make to
future global sea level rise.



FULL STORY ========================================================================== Newly discovered deep seabed channels beneath Thwaites Glacier in West Antarctica may be the pathway for warm ocean water to melt the underside
of the ice. Data from two research missions, using aircraft and ship,
are helping scientists to understand the contribution this huge and
remote glacier is likely to make to future global sea level rise.


========================================================================== Researchers from UK and US International Thwaites Glacier Collaboration
(ITGC), collected data from the glacier and adjoining Dotson and Crosson
ice shelves during January-March 2019. While one team collected airborne
data flying over the glacier and ice shelf in a British Antarctic Survey
Twin Otter aircraft, the other mapped the sea floor at the ice front
from the US Antarctic Program icebreaker RV Nathaniel B Palmer.

Publishing this month (9 September) in the journal The Cryosphere the two research papers describe the discovery. Thwaites Glacier covers 192,000
square kilometres (74,000 square miles) -- the size of Great Britain or
the US state of Florida -- and is particularly susceptible to climate
and ocean changes.

Over the past 30 years, the overall rate of ice loss from Thwaites and
its neighbouring glaciers has increased more than 5-fold. Already, ice
draining from Thwaites into the Amundsen Sea accounts for about four
percent of global sea-level rise. A run-away collapse of the glacier
could lead to a significant increase in sea levels of around 65 cm
(25 inches) and scientists want to find out how quickly this could happen.

Lead author Dr Tom Jordan, an aero-geophysicist at British Antarctic
Survey (BAS), who led the airborne survey, says: "It was fantastic to be
able to map the channels and cavity system hidden beneath the ice shelf;
they are deeper than expected -- some are more than 800 metres deep. They
form the critical link between the ocean and the glacier.



==========================================================================
"The offshore channels, along with the adjacent cavity system, are
very likely to be the route by which warm ocean water passes underneath
the ice shelf up to the grounding line, where the ice meets the bed."
Dave Porter at LDEO Columbia University, who flew over Thwaites Glacier
for the airborne survey, says: "Flying over the recently-collapsed
ice tongue and being able to see first-hand the changes occurring at
Thwaites Glacier was both awe inspiring and disconcerting, but also
gratifying to know the airborne data we were collecting would help
reveal the hidden structures below." Exceptional sea-ice break up in
early 2019 enabled the team on the RV Nathaniel B Palmer to survey over
2000 square kilometres of sea floor at the glacier's ice front. The
area surveyed had previously been hidden beneath part of the floating
ice shelf extending from Thwaites Glacier, which broke off in 2002, and
in most subsequent years the area was inaccessible due to thick sea-ice
cover. The team's findings reveal the sea floor is generally deeper and
has more deep channels leading towards the grounding line under the ice
shelf than was previously thought.

Lead author, Dr Kelly Hogan, is a marine geophysicist at BAS. She was
part of the team surveying the seabed. She says: "We found the coastal
sea floor, which is incredibly rugged, is a really good analogue for
the bed beneath the present-day Thwaites Glacier both in terms of its
shape and rock type. By examining retreat patterns over this sea-floor
terrain we will be able to help numerical modellers and glaciologists
in their quest to predict future retreat.



========================================================================== "This research has filled a critical data gap. Together the new coastal
sea floor maps and the cavity maps track the deep channels for over
100 km to where the glacier sits on the bed. For the first time we
have a clear view of the pathways along which warm water can reach the underside of the glacier, causing it to melt and contribute to global
sea-level rise." Glossary Ice shelf -- is a large floating platform of
ice that forms where a glacier or ice sheet flows down to a coastline
and onto the ocean surface. Ice shelves are only found in Antarctica, Greenland, Canada, and the Russian Arctic.

Ice sheet -- also known as a continental glacier, is a mass of glacial
ice that covers surrounding terrain and is greater than 50,000 km2
(19,000 sq mi).

Glacier -- is a huge mass of ice that moves slowly over land. The term "glacier" comes from the French word glace (glah-SAY), which means ice.

Glaciers are often called "rivers of ice."

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


========================================================================== Journal References:
1. Tom A. Jordan, David Porter, Kirsty Tinto, Romain Millan,
Atsuhiro Muto,
Kelly Hogan, Robert D. Larter, Alastair G. C. Graham, John
D. Paden. New gravity-derived bathymetry for the Thwaites, Crosson,
and Dotson ice shelves revealing two ice shelf populations. The
Cryosphere, 2020; 14 (9): 2869 DOI: 10.5194/tc-14-2869-2020
2. Hogan, K. A., Larter, R. D., Graham, A. G. C., Arthern, R.,
Kirkham, J.

D., Totten Minzoni, R., Jordan, T. A., Clark, R., Fitzgerald,
V., Waahlin, A. K., Anderson, J. B., Hillenbrand, C.-D., Nitsche,
F. O., Simkins, L., Smith, J. A., Gohl, K., Arndt, J. E., Hong,
J., and Wellner, J. Revealing the former bed of Thwaites Glacier
using sea-floor bathymetry: implications for warm-water routing
and bed controls on ice flow and buttressing. The Cryosphere, 14,
2883-2908, 2020 DOI: 10.5194/ 10.5194/tc-14-2883-2020 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200908200535.htm

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