Satellite image shows iceberg breakup the size of London 0:55
(CNN) --
Antarctic sea ice has hit record lows for the second time in two years, and some scientists are alarmed that the drastic drops represent a sign that the climate crisis may now be more clearly weighing on this vast region, complex and isolated.
Sea ice bordering Antarctica dropped to just 1.91 million square kilometers as of February 13, according to the National Snow and Ice Data Center (NSIDC), down from the previous record of 1.92. million square kilometers established on February 25 of last year.
Antarctic sea ice reaches its lowest level on record
Sea ice could further shrink;
the austral summer low may not be reached for another week.
The past two years mark the only time sea ice levels have fallen below 2 million square kilometers since satellites began monitoring it in 1978.
Ted Scambos, a glaciologist at the University of Colorado at Boulder, told CNN that "it's not just a record low. It's on a very steep downward trend."
Ocean area with at least 15% sea ice.
Credit: Credit: National Snow and Ice Data Center
Unlike the Arctic, where the rate of sea ice loss has followed a fairly constant downward trajectory as climate change accelerates, Antarctic sea ice extent has oscillated up and down, making it more difficult to figure out how the continent and the ocean surrounding it are responding to global warming.
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The two polar regions are very different.
While the Arctic is an ocean surrounded by continents, Antarctica is a continent surrounded by ocean, which means that its sea ice can grow outward, without being bound by land.
Antarctic ice tends to be thinner than Arctic ice, with higher highs in winter and steeper dips in summer.
Climate models predicted a decline in Antarctic sea ice similar to that in the Arctic, but until recently the region behaved completely differently from those predicted by those models.
The region reached a record winter sea ice extent in 2014, when it reached 19 million square kilometres, which seemed to support the idea that Antarctica might be relatively insulated from global warming.
But in 2016, something changed.
Scientists began to observe a pronounced downward trend.
At first, some blamed it on the usual variability of this enormously complex continent, with its diverse and intertwined weather systems.
But after two consecutive records for low sea ice, scientists are starting to worry.
"The question is: has climate change reached Antarctica? Is this the beginning of the end? Will the summer sea ice disappear for good in the next few years?" Christian Haas, head of the Research Section, told CNN. Sea Ice Physics from the Alfred Wegener Institute in Germany.
The graph shows the annual minimum extent of Antarctic sea ice from 1979 to 2023. Credit: National Snow and Ice Data Center
There are a number of factors that can play into why sea ice is so low, including winds, ocean currents, and ocean heat.
Air temperatures have been higher than usual in parts of Antarctica, about 1.5°C above the long-term average.
Another important consideration is the belt of westerly winds that encircles Antarctica, known as the Southern Annular Mode or Antarctic Oscillation.
These winds, which can increase sea ice melt, have been stronger than usual, according to the NSIDC, adding to weather conditions pumping warm air into the region.
The force of the winds has been related, in part, to the increase in pollution that warms the planet, as well as to the hole in the ozone layer over the continent.
It has also been suggested that sea ice could be melting due to heat trapped just below the ocean's surface, Scambos said.
"Basically, the heat is stirring up in the upper layer [of water] around Antarctica," he said.
If that theory holds up, and it is related to general warming of the oceans, "then that has big implications for the stability of the Antarctic ice sheet."
The disappearance of sea ice may have cascading effects in Antarctica and beyond.
Although it does not directly affect sea level, because it is already floating in the ocean, the loss of the band of sea ice surrounding Antarctica leaves coastal ice sheets and glaciers exposed to waves and warm ocean waters, making it which makes them much more vulnerable to melting and breaking.
A disturbed Antarctic landscape could have major impacts on its fauna, from the microorganisms and algae that butt up the food chain, food for the krill that, in turn, feeds many of the region's whales, to the penguins and seals that depend on the sea ice for feeding and resting.
Adélie penguins on Paulet Island in the Weddell Sea, near the tip of the Antarctic Peninsula.
Credit: Wolfgang Kaehler/LightRocket via Getty Images
Some areas of Antarctica have been experiencing alarming changes for some time.
The Antarctic Peninsula, a long range of icy mountains that juts out from the west side of the continent like a thumb toward South America, is one of the fastest warming places in the Southern Hemisphere.
Carlos Moffat, an oceanographer at the University of Delaware, who just returned from a research trip to the Antarctic Peninsula, told CNN that the scarcity of sea ice and very warm ocean temperatures they found "are dramatically different from what we've seen." observed in recent decades.
Moffat, who visits the region each summer as part of the Palmer Long-Term Ecological Survey, said: "This year's conditions are set against the backdrop of long-term change in this region of Antarctica."
Last year, scientists claimed that West Antarctica's vast Thwaites Glacier, also known as the "Doomsday Glacier," was "in trouble" as the planet warms, with a possible rapid retreat in the coming years.
Scientists have calculated that sea level rise could increase by about 3 meters if Thwaites collapsed completely, devastating coastal communities around the world.
The famous "glacier at the end of the world" is "in trouble", say scientists after finding surprising formations under the ice shelf
It's too early to say if record sea ice declines are the new normal or will pick up, and Antarctica is notorious for major swings.
The NSIDC notes that: "While 2022 and 2023 have had record low extensions, four of the five highest lows have occurred since 2008."
"It's going to take a while to figure it out," Scambos said.
"We are still reacting to a relatively sudden turnaround. Certainly the last few years have been a dramatic exclamation point in a trend that was only just developing after 2016."
Scientists will need at least another five years of data and observations, he estimated, but added: "It does seem that something has changed in Antarctica and things are quite drastic."
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