Antarctic glaciers are losing ice the fastest in 5,500 years

At the current rate of retreat, the vast glaciers, which extend deep into the heart of the ice sheet, could contribute as much as 3.4 meters to global sea level rise in the coming centuries.

Antarctica is covered by two massive ice masses: the East and West Antarctic Ice Sheets, which feed many individual glaciers. Due to the warming climate, the WAIS has thinned out at an accelerated rate in recent decades. Within the ice sheet, the Thwaites and Pine Island glaciers are particularly vulnerable to global warming and are already contributing to sea level rise.

Now, a new study led by the University of Maine and the British Antarctic Survey, including academics from Imperial College London, has measured the rate of local sea level change — an indirect way of measuring ice loss — around these particularly vulnerable glaciers.

They found that the glaciers have begun to retreat at a rate not seen in the past 5,500 years. With areas of 192,000 km2 (almost the size of the island of Great Britain) and 162,300 km2 the Thwaites and Pine Island glaciers respectively have the potential to cause major rises in global sea levels.

Co-author Dr. Dylan Rood of Imperial’s Department of Earth Science and Engineering said: “We reveal that while these fragile glaciers have been relatively stable over the past millennia, their current rate of retreat is accelerating and global sea levels are already rising.

“These currently elevated ice melt rates may signal that those vital arteries of the heart of the West Antarctic ice sheet have ruptured, leading to an accelerating current in the ocean that is potentially disastrous for future global sea levels in a warming world.” is it too late to stop the bleeding?”

The newspaper is published in Natural Geosciences

Search for sea shells

During the mid-Holocene, more than 5,000 years ago, the climate was warmer than it is today, resulting in higher sea levels and smaller glaciers. The researchers wanted to study fluctuations in sea level since the middle Holocene, so they studied the remains of ancient Antarctic beaches, which are today elevated above modern sea level.

They examined seashells and penguin bones on these beaches using radiocarbon dating — a technique that uses the radioactive decay of carbon locked in the shells and bones like a clock to tell us how long they’ve been above sea level.

When heavy glaciers sit on land, they push or ‘load’ the Earth’s surface. After the ice is melted or ‘discharged’ from the glaciers, the land ‘rebounds’ so that what was once a beach is now higher than sea level. This explains why the local sea level for this country dropped, while globally the water from the melting ice caused the global sea level to rise.

By determining the precise age of these beaches, they were able to see when each beach appeared and thereby reconstruct the changes in the local or ‘relative’ sea level over time.

The results showed a steady decline in relative sea levels over the past 5,500 years, which the researchers interpret as a result of ice loss just prior to that time. This pattern corresponds to relatively stable glacier behavior with no evidence of large-scale glacier loss or advance.

They also showed that the relative sea level drop since the mid-Holocene was nearly five times smaller than measured today. The scientists found that the most likely reason for such a large difference is the recent rapid loss of ice mass.

The researchers also compared their results with existing global models of the dynamics between ice and the Earth’s crust. Their data showed that based on their data, the models do not accurately reflect the history of the area’s sea level rise during the mid to late Holocene. This study helps to paint a more accurate picture of the region’s history.

While their data do not rule out the possibility of minor fluctuations of the Thwaites and Pine Island glaciers over the past 5,500 years, the researchers concluded that the simplest interpretation of their data is that these glaciers have been relatively stable from the mid-Holocene to recently. — and that the current rate of glacier retreat, which has doubled in the past 30 years, is indeed unprecedented in the past 5,500 years.

Lead author Professor Brenda Hall of the University of Maine said: “Relative sea level changes allow you to see the large-scale loading and unloading of the Earth’s crust by ice. For example, glacial realization, which would result in crust loading, would increase the speed of slowing the Earth’s crust. relative drop in sea level or possibly even lead to submergence of the land below sea level.”

Stop the bleeding

To better predict the future fate of the ice sheet and its impact on global sea levels, the International Thwaites Glacier Collaboration (ITGC) – the largest joint UK-US field science program ever conducted in Antarctica – involving Imperial- researchers involved will improve our understanding of the past behavior of the Thwaites Glacier during climate conditions similar to today’s.

Important clues are also buried deep under the ice. To solve these mysteries, the researchers will drill through the glacial ice to collect rock beneath, which may provide evidence as to whether the current accelerating melt rates are reversible or not.

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