FAREWELL TO ANTARCTICA
FAREWELL TO ANTARCTICA
The continent of Antarctica is covered in ice year-round, but its ice sheets retreat and advance in annual cycles. And that’s a pattern that has been going on for thousands of years. Nowadays, clues from the geologic record suggest that climate change is causing Antarctica to lose ice faster than in the past.
The ancient ice sheets leave signs of their presence in the land they covered. This is revealed when retreating glaciers expose the ground they once covered. Researchers detect markers of where ice sheets once covered Antarctica by looking at the seabed around the western part of the continent. This holds traces of where glaciers were pinned in the past.
The pace of ice retreat in Antarctica was estimated in the past to be about 164 feet each year — between glacial cycles. But today, ice retreat is about more than 20 times that rate — more than 3,200 feet per year.
The annual ice loss was detected in West Antarctica – around 58 billion tons until 2012 – went up to 175 billion tons per year in the next five years. Also, in the Antarctic Peninsula, the annual rate of ice loss increased from around 7 billion tons to 36 billion tons.
“These glaciers will keep retreating for decades and even centuries to come and we can’t stop it. A large sector of the West Antarctic Ice Sheet has passed the point of no return,” said Eric Rignot, a glaciologist at the University of California, Irvine, and NASA’s Jet Propulsion Laboratory in Pasadena, Calif.
If West Antarctica melts completely, sea level is predicted to raise by 11 to 13 feet.
“The satellite measurements tell us that the ice sheet is much more dynamic than we used to think,” Andrew Shepherd, professor of Earth observation with the School of Earth and Environment at the University of Leeds in the U.K., said to Live Science.
THE VANISHING CONTINENT
In 25 years, about 3 trillion tons of ice vanished from Antarctica. Only one iceberg that broke off of the Larsen C ice block – in July 2017 – was weighing over 1 trillion tons.
“If you take a look at the first Intergovernmental Panel on Climate Change assessment report — 30 years ago, before we had satellite measurements of the polar regions — you’ll see that the ice sheets were not expected to respond to climate change at all. The general consensus in glaciology was that ice sheets couldn’t change rapidly — but that’s not the case,” Shepherd said.
The ice shelves in Antarctica have been in place for about 10,000 years.
“The fact that they’re collapsing today is unprecedented, and the pace of retreat and collapse of ice shelves is many times faster than we would expect from the normal glacial cycles,” Shepherd said.
“One of the most striking features is they have been reacting almost simultaneously,” Rignot said.