Satellite image of the front of Thwaites Glacier, West Antarctica
NASA/USGS, processed by Dr. Fraser Christie, Scott Polar Institute, University of Cambridge
Norway’s ancient ice sheets may have retreated more than 600 meters per day at the end of the last ice age.
This is 10 times faster than previous estimates and suggests that the current ice sheet could be melting on the ocean floor at a much faster rate than scientists previously thought, said the University of Newcastle, UK. said Christine Batchelor of
“Potentially, it shows that ice sheets can physically retreat at rates an order of magnitude faster than what has been seen so far. [before],” she says.
The ice sheet is attached to the bedrock of the seafloor, and as sea temperatures rise, the junction between the seafloor ice and the ocean melts and breaks the bond, leaving that portion of the ice floating as an ice shelf. The boundary line of ice attached to the bedrock is called the ground line.
For the past 50 years, scientists have used satellite data to track the location of the grounding lines of the Antarctic and Greenland ice sheets. Recession of the grounding wire has caused global sea level to rise by an estimated 0.7 mm per year since the 1990s so far.
But Bachelor and her colleagues wondered if satellite data might not tell the whole story. They decided to delve into the history of changes in the ground line at the end of the last Ice Age, 15,000 to 19,000 years before her. At that time, Batchelor says the Scandinavian ice sheet began to retreat as the climate began to warm as part of the natural heating and cooling cycle.
She and her colleagues noticed that retreating ice sheets leave long-term trails in seafloor sediments called corrugated ridges. Because these features form under ocean waves, they can remain undisturbed for thousands of years, providing a historical record of glacier melt, she says.
Batchelor and her team used a ship-based device to map the seafloor topography across 30,000 square kilometers of Norway’s central continental shelf, including 7678 wavy ridges.
They found evidence that the ancient ground wire retreated up to 610 meters per day. 70% of the region shows recession of more than 100 meters per day, at least during ‘pulses’ that can last from days to months. This value far exceeds previously reported rates of ground-wire recession from the satellite and oceanic geological records, Batchelor said.
The rate of this retreat was particularly high along flatter areas of the seafloor, she added.
Applied to the present, the findings suggest that an estimated melt rate of tens of centimeters per day in West Antarctica could cause ground ice retreat of up to hundreds of meters per day, especially across low-slope regions. suggests that
This can be a particular problem at Antarctica’s Thwaites Glacier. Thwaites Glacier is grounded in a very flat floor by its central trunk.
“This will have far-reaching effects that are now receding in key areas of Antarctica where future sea-level rise is a concern,” said Adam Sproson of the Japan Agency for Marine-Earth Science and Technology.
“Such extreme ground wire recession rates have not been observed in modern times, [period]these results from the geological record, along with numerical models of ice sheet behavior, suggest that rapid and widespread groundline retreat is possible under present-day Antarctic climatic conditions.” Sproson says.
“This suggests that if major regions of Antarctica currently observing increased rates of retreat, such as the Amundsen Sea region, accelerate to levels recorded by Bachelor, they could have a significant impact on future global sea level rise. there is. [and her team]”
topic:
