The research vessel JOIDES Resolution surrounded by sea ice as it approaches Antarctica's eastern Ross Sea during International Ocean Discovery Program (IODP) Expedition 374. Credit: Jenny Gales/University of Plymouth
Scientists
have discovered the cause of giant underwater landslides in Antarctica, which
they believe could have generated tsunami waves that stretched across the
Southern Ocean.
An international team of researchers has
uncovered layers of weak, fossilized and biologically-rich sediments hundreds
of meters beneath the sea floor.
These formed beneath extensive areas of underwater landslides, many of which cut more than 100 meters into the
seabed.
Writing in Nature
Communications, the scientists say these weak layers—made up of historic
biological material—made the area susceptible to failure in the face of
earthquakes and other seismic activity.
They also highlight that the layers
formed at a time when temperatures in Antarctica were up to 3°C warmer than
they are today, when sea levels were higher and ice sheets much smaller than at
present.
With the planet currently going through
a period of extensive climate change—once again including warmer waters, rising
sea levels and shrinking ice sheets—researchers believe there is the potential
for such incidents to be replicated.
Through analyzing the effects of past
underwater landslides, they say future seismic events off the coast of
Antarctica might again pose a risk of tsunami waves reaching the shores of South America, New
Zealand and South East Asia.
Professor Rob McKay (Director of the
Antarctic Research Centre at Victoria University of Wellington and co-chief
scientist of IODP Expedition 374) and Dr Jenny Gales (Lecturer in Hydrography
and Ocean Exploration at the University of Plymouth) examine the half-section
of a core recovered from the Antarctic seabed. Credit: Justin Dodd
The
landslides were discovered in the eastern Ross Sea in 2017 by an international
team of scientists during the Italian ODYSSEA expedition.
Scientists revisited the area in 2018 as
part of the International Ocean Discovery Program (IODP) Expedition 374 where
they collected sediment cores extending hundreds of meters beneath the sea
floor.
By analyzing those samples, they found
microscopic fossils which painted a picture of what the climate would have been
like in the region millions of years ago and how it created the weak layers
deep under the Ross Sea.
The new study was led by Dr. Jenny
Gales, Lecturer in Hydrography and Ocean Exploration at the University of
Plymouth, and part of IODP Expedition 374.
She said, "Submarine landslides are a major geohazard with the potential to trigger tsunamis that can lead to huge loss of life. The landslides can also destroy infrastructure including subsea cables, meaning future such events would create a wide range of economic and social impacts. Thanks to exceptional preservation of the sediments beneath the sea floor, we have for the first time been able to show what caused these historical landslides in this region of Antarctica and also indicate the impact of such events in the future. Our findings highlight how we urgently need to enhance our understanding of how global climate change might influence the stability of these regions and potential for future tsunamis."
Drilling into the seabed of the Ross Sea during
International Ocean Discovery Program (IODP) Expedition 374 to recover one of
the hundreds of cores which helped scientists assess the cause of historic
landslides. Credit: Laura de Santis
Professor Rob McKay, Director of
the Antarctic Research Centre at Victoria University of Wellington and co-chief
scientist of IODP Expedition 374, added, "The main aim of our IODP
drilling project in 2018 was to understand the influence that warming climate
and oceans have had on melting Antarctica's ice sheets in the past in order to
understand its future response. However, when Dr. Gales and her colleagues on
board the OGS Explora mapped these huge scarps and landslides the year before,
it was quite a revelation to us to see how the past changes in climates we were
studying from drilling were directly linked to submarine landslide events of this magnitude. We did not expect to
see this, and it is a potential hazard that certainly warrants further
investigation."
Laura De Santis, a researcher at
the National Institute of Oceanography and Applied Geophysics in Italy, and
also co-chief scientist of IODP Expedition 374, explained, "The sediment cores we analyzed were obtained as part of IODP, the
international sea floor scientific drilling project that has been active in the
field of geoscience for over 50 years. The project aims to explore the history
of planet Earth, including ocean currents, climate change, marine life and mineral deposits, by studying sediments and
rocks beneath the sea floor."
Jan Sverre Laberg, from The Arctic
University of Norway, Tromsø, said, "Giant submarine landslides have
occurred both on southern and northern high latitude continental margins,
including the Antarctic and Norwegian continental margins. More knowledge on
these events in Antarctica will also be relevant for submarine geohazard
evaluation offshore Norway."
Dr. Amelia Shevenell, Associate
Professor of Geological Oceanography at University of South Florida, College of
Marine Science, noted, "This study illustrates the importance of
scientific ocean drilling and marine geology for understanding both past
climate change and identifying regions susceptible to natural hazards to inform
infrastructure decisions. Large landslides along the Antarctic margin have the
potential to trigger tsunamis, which may result in substantial loss of life far
from their origin. Further, national Antarctic programs are investigating the
possibility of installing submarine cables to improve communications from
Antarctic research bases. Our study, from the slope of the Ross Sea, is located
seaward of major national and international research stations, indicating that
marine geological and geophysical feasibility studies are essential to the
success of these projects and should be completed early in the development
process, before countries invest in and depend on this communication
infrastructure."
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