Rapid retreat of the glacier may raise global sea levels by 3-10 feet
The amount of ice lost from Antarctica’s “doomsday glacier” Thwaites Glacier has doubled in the last 30 years, and it is likely to retreat faster than current rates in the coming years, a new study warned.
Roughly the size of Spain, the glacier is melting from the button in contact with warm water. This increases the risk of glacier collapse within the next few decades, according to the United States National Aeronautics and Space Administration.
In the last 200 years, there was a period of six months when the Thwaites Glacier retreated at a rate more than 2.1 kilometres per year,
This is twice the rate between 2011 and 2019. “The results show that there are times when pulses of fast retreat take place at Thwaites — faster than we are witnessing right now,” Alastair Graham from the University of South Florida’s College of Marine Science and lead author told Down to Earth.
“Thwaites is really holding on today by its fingernails, and we should expect to see big changes over small timescales in the future,” marine geophysicist and study co-author Robert Larter from the British Antarctic Survey said in a statement.
Researchers measure the retreat using satellite observations from the last 40 years. Data from the past 10,000 years are scarce, the researchers wrote in their study.
Researchers from the United States, United Kingdom and Sweden imaged the seabed on which the glacier rested between 200 years and the present day, the researchers said.
Imaging the seabed gave the team a glimpse of what the glacier looked like in the pre-satellite era. This, they said, can help researchers understand how it might change in the future.
They specifically looked at the former grounding line of the glacier — the edge where the bottom of the glacier sits on bedrock. The threatened Thwaites glacier sits on ridges or underwater mountains, experts noted.
The former grounding line on the seabed has geological features called ribs. They are tens of centimetres high and several metres wide, Graham explained. “They look like tractor tyre marks in the rocky mud that cover the ocean bottom at the front of Thwaites,” he added.
Using autonomous underwater vehicles and geophysical sensors, the team mapped the sea bed at a high resolution, allowing them to see the ribs.
“We were able to confidently show that the ribs are a time series,” said Graham. “And from that, we were able to work out very precise rates of retreat for an interval of time about six months in duration,” he added.
The fast retreat pulse shown in the study can be explained entirely by the warmer water melting the glacier from underneath, as seen in recent times.
Alternatively, Graham added, a small kick from thinning at the bottom of the ice shelf – a thick mass of floating ice jutting out of the land and into the sea – could trigger a pulse of fast retreat.
This “leads to a bigger response as the glacier unzips from its seabed – something that we might call dynamic thinning,” he highlighted.
In the future, the team hopes to study the seabed sediments directly to date the ribs on the seabed more accurately.
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