Ice reduction in Antarctica breaks record this year – 08/13/2023 – Environment

It’s winter in the Southern Hemisphere, a time when ice usually forms around Antarctica. But this year that growth has stunted, hitting a record low by a wide margin.

The sharp drop in sea ice is alarming scientists and raising concerns about its vital role in regulating ocean and air temperatures, circulating ocean water and maintaining an ecosystem crucial for everything from microscopic plankton to iconic penguins. from the mainland.

“This year is really different,” said Ted Scambos, a senior fellow at the University of Colorado Boulder and an Antarctic expert at the US National Snow and Ice Data Center (NSIDC). “It’s a very sudden change.”

A continued decline in Antarctic sea ice would have global consequences by exposing more of the continent’s ice sheet to the open ocean, allowing it to melt and break up more easily, contributing to sea level rise, which affects populations. coastlines around the world.

Less ice also means less protection from the sun’s rays, which can raise the temperature of the water, making it harder to freeze.

At the end of June, ice covered 11.7 million km2 of ocean around the continent, according to NSIDC data. That’s almost 2.6 million km² less than the average expected in approximately 40 years of satellite observations.

The clear difference from previous years is surprising, as sea ice around Antarctica has been slower to respond to climate change than ice in the Arctic Ocean.

Southern Ocean ice also hit a record reduction in 2022, but this year’s ice cover is nearly 1.3 million km² less.

“The low sea ice extent in Antarctica in 2023 is unprecedented in the satellite record,” Liping Zhang, project scientist at the U.S. National Oceanic and Atmospheric Administration’s Geophysical Fluid Dynamics Laboratory, wrote in an email.

The record decrease could signal a shift in the sea ice system to a new, unstable state where extremes become more common, but Zhang cautioned that scientists were still investigating that question.

Sea ice around Antarctica typically forms from February to August and then melts through the following winter in the Southern Hemisphere. Various ocean and atmospheric patterns influence how much ice grows or shrinks, and the overlapping interactions between these forces are complex. .

In addition to these short-term natural patterns, there is the long-term influence of humans burning fossil fuels, adding greenhouse gases to the atmosphere. Some researchers suspect that we are finally seeing the effects of this burning on once-resistant Antarctic sea ice.

This year’s change, in the context of several consecutive years of less sea ice, is “very, very concerning,” said Marilyn Raphael, professor of geography and director of the Institute for the Environment and Sustainability at the University of California, Los Angeles. “It’s not within natural variability.”

Raphael has been working to extend the historical record of Antarctic sea ice before the 1970s, when satellite observations began. She and her colleagues recently published a new dataset dating back to 1905, using meteorological observations to reconstruct sea ice extent during previous years.

While data is still limited, the longer record captures more cycles of natural variability. Raphael and other experts believe that the ocean, which warms more slowly than the atmosphere and has absorbed much of the heat from burning fossil fuels, may have reached a point where that heat is affecting Antarctic sea ice.

Sea surface temperatures have broken records this year, and there are currently three exceptionally warm patches of water around Antarctica. While other factors are also at play, these hot spots line up with coastal areas where sea ice has been forming unusually slowly, Scambos said.

_{Translated by Luiz Roberto M. Gonçalves}