The most dramatic impact may be taking place under the cover of Antarctic night during a summer of record heat. Every summer—or winter, in the southern hemisphere—sea ice forms a halo around the continent at the bottom of the world, but this year has been anything but typical. Scientists have watched in disbelief as sea-ice growth stops in ways that have never before happened in modern times. In contrast to ice on land, sea ice has very little impact on the level of the oceans. However, the lack of recovery has entered the “six sigma” zone, a mysterious scientific phrase used to describe the exceptional circumstances that are currently taking place.
Between February and March is typically when Antarctic sea ice reaches its lowest point before gradually regrowing over the following six months. It has had a difficult time recovering after reaching a record low this year in February. According to a study done by the National Snow and Ice Data Centre (NSIDC), there was a piece of ice missing as of mid-July that was the size of Argentina. In the nearly 45-year-old satellite record of Antarctic sea ice, that represents a record low for this time of year. However, “record low” doesn’t fully capture it. Introducing “six sigma.” Sigmas are used by scientists to standardize data and make it simpler to compare and test hypotheses by referring to departures from the norm.
An event that falls within the one-sigma range can be considered to be quite typical
An event that falls within the one-sigma range can be considered to be quite typical. When you reach two sigma, you start to enter slightly strange terrain, and three sigma events are outside of the normal range. Lettie Roach, an associate research scientist at the NASA Goddard Institute for Space Studies and Columbia University, claims that the sea ice was at or near that level in June. A five or six-sigma occurrence, however, is extraordinary. An austral winter like this one is thought to occur only approximately once every 7.5 million years, according to researchers. Even more eye-watering odds have come from time to time, but concentrating on a single day doesn’t convey the whole story.
“It’s now a larger departure from average conditions than we’ve seen in the Arctic,” said Julienne Stroeve, a senior scientist at NSIDC. (Research published last year shows the Arctic is infamously heating up roughly four times faster than the rest of the planet.) All around the continent, ice is disappearing, although it is especially noticeable close to the Antarctic Peninsula and in regions to the north of the Weddell Sea. According to Stroeve, the situation has been so precarious that two postdoctoral researchers she collaborates with who are working on the peninsula installed equipment on the little bit of ice that was present, only to lose their equipment when a storm passed through and broke up the ice.
The land ice of Antarctica and the floating ice shelves that serve as buttresses to prevent it from melting into the ocean and raising sea levels are both under siege by warming
“It’s been a very bad winter for our research there because there hasn’t been any sea ice in that area,” said Stroeve, who also works at the University of Manitoba as a Canada 150 research chair. “It’s too soon to say for certain but all climate models have suggested the Antarctic sea ice should be shrinking in response to anthropogenic warming.” Globally, seas and land have been scorched by sweltering temperatures. According to research released on Tuesday, July’s heat in the US and southern Europe would have been “virtually impossible” without climate change providing a significant background boost. The Antarctic continent and its sea ice have suffered as a result of climate change, however, scientists are still trying to figure out exactly what is happening there.
Sea ice has been increasing gradually but steadily through the middle of the 2010s, but then suddenly started to decline. Sea ice levels in the area reached historic lows in 2017, however, the record was then broken the following year, again in 2022, and once again this year. Natural climate changes are partially to blame; for example, because Antarctic sea ice originates around the continent rather than in a basin like Arctic sea ice, it is more brittle and vulnerable to external factors like El Nino.
The land ice of Antarctica and the floating ice shelves that serve as buttresses to prevent it from melting into the ocean and raising sea levels are both under siege from warming. When it comes to comprehending the status of the planet and the potential role that the distant expanses of Antarctica may play in modifying coastlines, one of the most urgent scientific concerns is how all these many types of ice, atmospheric patterns, and more lock together. “I think the recent events really highlight that we have more to do to understand the drivers of these important changes we’re seeing in the sea ice, ocean, land ice, and atmosphere in Antarctica,” Roach said.