2023-07-30 08:59:00
(CNN) — As the northern hemisphere swelters under an unprecedented summer heatwave, far to the south, in the dead of winter, another terrifying climate record is being broken. Antarctic sea ice has fallen to unprecedented levels for this time of year.
Each year, Antarctic sea ice reduces to its lowest levels towards the end of February, during the continent’s summer. Then the sea ice builds up again during the winter.
But this year scientists have observed something different.
Sea ice has not returned to anywhere near expected levels. In fact, it is at the lowest levels for this time of year since records began 45 years ago. The ice is about 1.6 million square kilometers below the previous winter record set in 2022, according to data from the National Snow and Ice Data Center (NSIDC).
As of mid-July, Antarctic sea ice was 2.6 million square kilometers below the 1981 to 2010 average. That’s an area almost as large as Argentina or the combined areas of Texas, California, New Mexico, Arizona , Nevada, Utah and Colorado.
“The Game Has Changed”
The phenomenon has been described by some scientists as exceptional off the charts, something that is so rare that it will most likely only occur once in millions of years.
But Ted Scambos, a glaciologist at the University of Colorado Boulder, said that speaking in these terms may not be all that helpful.
“The game has changed,” he told CNN. “It doesn’t make sense to talk about the probabilities of it happening the way the system used to be, it clearly tells us that the system has changed.”
Scientists are now scrambling to find out why.
The rate of melting in Antarctica is much faster than in the 1990s. (Credit: Gallo Images/Orbital Horizon/Copernicus Sentinel Data/Getty Images)
Antarctica is a remote and complex continent. Unlike the Arctic, where sea ice has had a constant downward trajectory As the climate crisis accelerates, Antarctic sea ice has swung from all-time highs to all-time lows in recent decades, making it difficult for scientists to understand how it is responding to global warming.
But since 2016, scientists have started to see a strong downward trend. While natural climate variability affects sea ice, many scientists say that climate change may be a major factor in the ice’s disappearance.
“The Antarctic system has always been highly variable,” Scambos said. “However, this level [actual] of variation is so extreme that something radical has changed in the last two years, but especially this year, relative to all previous years for at least 45 years.”
Several factors contribute to sea ice loss, Scambos said, including the strength of westerly winds around Antarctica, which have been linked to increased planet-warming pollution.
“Warmer ocean temperatures north of the Southern Ocean boundary mixing with water that is normally somewhat isolated from the rest of the world’s oceans is also part of this idea of how to explain this,” Scambos said.
At the end of February this year, Antarctic sea ice reached its lowest extent since records began, at 1,789,682 square kilometers.
This winter’s unprecedented occurrence may signal long-term change for the isolated continent, Scambos said. “It’s more likely that we won’t see the Antarctic system recover like it did, say, 15 years ago, for a very long period into the future, and possibly ‘never’.”
Others are more cautious. “It’s a big deviation from the average, but we know that Antarctic sea ice exhibits a lot of variability from year to year,” Julienne Stroeve, senior scientist at the National Snow and Ice Data Center, told CNN, adding that “it’s too soon to say if this is the new normal or not”.
cascading effects
Sea ice plays a vital role. While it doesn’t directly affect sea level rise, since it’s floating in the ocean, it does have indirect effects. Their disappearance leaves coastal ice sheets and glaciers exposed to waves and warm ocean waters, making them more vulnerable to melting and calving.
The lack of sea ice could also have significant impacts on its wildlife, including the krill that many of the region’s whales feed on, and the penguins and seals that rely on sea ice for food and rest.
More broadly, Antarctic sea ice contributes to the regulation of the planet’s temperature, meaning its disappearance could have cascading effects far beyond the continent.
Sea ice reflects incoming solar energy back into space, when it melts it exposes the darker ocean waters below which it absorbs the sun’s energy.
Parts of Antarctica have been undergoing alarming changes for a while. The Antarctic Peninsula, a spindly range of icy mountains jutting out from the west side of the continent, is one of the fastest warming places in the southern hemisphere.
Last year, scientists said West Antarctica’s vast Thwaites Glacier, also known as the “Doomsday Glacier,” was “hanging by nails” as the planet warms up.
Scientists have estimated that global sea level rise could increase by around three meters if Thwaites were to completely collapse, devastating coastal communities around the world.
Scambos said the record low level of sea ice this winter is a very alarming sign.
“In 2016, [el hielo marino antártico] suffered the first big fall. Since 2016, she has stayed low and now she has hit rock bottom. Something important in a large part of the planet is suddenly behaving differently than we have seen in the last 45 years.
— CNN’s Laura Paddison contributed to this report.
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