A ‘triple whammy’ of chaos has triggered a downward spiral in Antarctica, scientists discover

For decades, it was thought that Antarctica might be isolated from this species. Rapid ice melting in the Arctic. But that changed in 2015 when the sea ice surrounding this vast, icy continent stopped expanding and began to shrink dramatically. Scientists say they now understand why this is happening, and their findings spell big trouble for a region whose fate affects us all.

Antarctic sea ice has been on a steep downward trend for almost a decade. Reached record low in 2022 again in 2023when you fall only 691,000 square milesIt is equivalent to a greater loss of ice area from Greenland compared to average levels. This year saw higher amounts of sea ice at the peak of summer in the Southern Hemisphere, but this still at 16th lowest over nearly fifty years of record keeping.

Scientists have been working for years to understand what is causing the rapid decline in sea ice and whether it is a sign that Antarctica is entering a new state.

The new research identifies a number of different processes driven by intensifying winds and warming water that are “destabilizing” the ocean surrounding Antarctica. This amounts to “the triple whammy of climate chaos,” the report’s authors wrote in a press release accompanying the report. paperIt was published Friday in the journal Science Advances.

Aditya Narayanan, study author and research fellow in physical oceanography at the University of Southampton in the United Kingdom, said the chain of events began decades ago, when westerly winds around Antarctica began to strengthen.

The strength of these winds is also linked in part to increased pollution from the burning of fossil fuels, which is warming the planet. like a hole in the ozone layer over the continent.

These winds initially helped cool the surface ocean, but this changed over time as a slower, deeper response occurred. Starting around 2015, winds began to drag relatively warm, salty water from the depths of the ocean towards the surface. The heat melted the sea ice, and more salt on the surface made the water denser, affecting the way the ocean layers mixed and making it easier for more heat to move upward.

According to the study, a third phase began around 2018, after several years of sea ice decline. The region is stuck in a cycle where less sea ice means the water at the ocean surface remains salty and warm, thus preventing further ice formation.

“These three phases illustrate how long-term changes caused by climate change can trigger a series of processes that push the system towards a long-term low sea ice state,” Narayanan said.

The study noted differences between East Antarctica, where the retreat of sea ice is largely triggered by heat rising from the deep ocean, and West Antarctica, where the atmosphere plays a larger role as clouds carried by warm air help trap heat near the ocean surface.

Sea ice loss has wide ripple effects. As it disappears, it exposes coastal ice sheets and glaciers to waves and warmer ocean waters, making them much more vulnerable to melting and breaking up.

Sea ice also acts as a giant mirror, reflecting solar energy from Earth back into space. When it melts, it increases heating by revealing the dark ocean beneath that absorbs solar energy.

Loss of sea ice could accelerate global warming by disrupting the balance of currents that store heat and carbon in the ocean, scientists said.

Oscar Schofield, a biological oceanographer at Rutgers University who was not involved in the study, said the paper gives a good idea of ​​what’s going on in Antarctica.

Clarifying the causes of sea ice loss “will help us understand why things are changing and potentially predict the future with more confidence,” he told CNN. There is still debate about what the future holds for Antarctica, but “the observed declines are striking,” he added.

Ted Scambos, a senior research scientist at the Earth Science and Observation Center at the University of Colorado Boulder, said the study provides “a more coherent story of changes in Antarctic sea ice extent over the past 10 years.” Looking forward, Scambos, who was not involved in the research, said: “I agree that Antarctic sea ice is unlikely to recover.”

Alberto Naveira Garabato, report author and physical oceanographer at the University of Southampton, said if low sea ice levels persist into 2030 and beyond, the effects could be huge: “The ocean could move from being a stabilizer of the world’s climate to a powerful new driver of global warming.”

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