Sea ice in Antarctica reaches new lows

Six Adelie penguins are gathered together on a piece of ice in Antarctica

Since we started using satellites to measure it in the late 1970s, there is currently less sea ice surrounding the Antarctic continent than at any other time.

According to the National Snow and Ice Data Center, this year is exceptional even though it is the summer in the southern hemisphere, when you would expect less sea ice.

On February 13, coverage was only 1.91 million square kilometers (737,000 square miles) due to winds, warmer air, and water.

Additionally, this summer's melt still has a ways to go.

Last year, it took until 25 February to reach the previous record-breaking minimum of 1.92 million sq km (741,000 sq miles).

In the past seven years, three years with record-low sea ice have occurred: 2017, 2022, and now 2023.

Line chart showing the rolling 5-day average measure of sea-ice extent in Antarctica with one line per year since 1979. The three most recent years have been highlighted: in 2017 a record was set in early March; this was broken in February 2022 and again in February 2023

As they travel around the continent, research, cruise, and fishing ships are all describing a similar scene: the majority of sectors are essentially ice-free.

The only area still dominated by frozen floes is the Weddell Sea.

The behavior of Antarctic sea ice is thought by scientists to be a complex phenomenon that cannot just be attributed to climate change.

The sea-ice extent exhibits significant variability when data from the last 40 or so years of available satellite data are considered. Only in the last few years has there been a noticeable decline in the summer ice volume.

Line chart which depict the lowest point of measured sea-ice each year from 1979 to 2023. Although the line fluctuates considerably, there is a slight downward trend in recent years ending with a new record set in 2023 at 1.91 million square kilometres

In line with what we have observed in the Arctic, where summer sea-ice extent has been decreasing by 12–13% per decade as a result of global warming, computer models had predicted that it would exhibit long-term decline.

But that hasn't been how the Antarctic has acted.

We can look back at least as far as 1900 using data from sources other than satellites.

These show that Antarctic sea ice was declining at the beginning of the last century before beginning to increase.

With record satellite winter maximums and now record satellite summer minimums, it has recently displayed significant variability.

The floes can cover up to 18 million square kilometers (6.9 million square miles) during the winter.

In general, it is what the summer ice pack this year lacks compared to the longer-term average. The British Isles are covered by that.

Map of the United Kingdom and Ireland covered completely by a shaded circle representing 0.91 million square kilometres - the amount of sea ice that is missing in Antarctica

It will soon begin to grow once more, and for a variety of reasons, it is crucial that it does.

Seawater that has frozen at the ocean's surface loses salt, which makes the water below denser and causes it to sink.

This is a component of the water mass movement that powers the great ocean conveyor, which helps control energy in the climate system.

The importance of sea ice to life at the poles cannot be overstated.

The small crustaceans known as krill, which are a staple food source for whales, seals, penguins, and other birds, are fed on the algae that adheres to the ice in the Antarctic.

Some species will haul out and rest on the sea ice as a platform.

The unusually hot air temperatures to the west and east of the Antarctic Peninsula most likely contributed to this year's record sea-ice minimum.

These have been 1 point 5C higher than average over the long term.

Map of Antarctica with colour shading to represent the difference between the average surface air temperature in 2022 and the average temperature during the reference period 1991-2020. Aside from two colder blue patches, the continent is mostly red -- about 1 degree above average. Areas over the peninsula are a dark red, up to 3 degrees above average.

The Southern Annular Mode (SAM), a significant player in the area, is another thing that exists.

It describes changes in the area's atmospheric pressure, which has an impact on the continent's well-known westerly winds that circle it.

The mode is reportedly currently in a strongly positive phase.

This intensifies the current westerly winds and pushes them poleward.

Flutes are broken up and pushed northward into warmer waters by increased storminess, where they melt out.

The presence of an ozone hole over Antarctica and the increase in greenhouse gases in the atmosphere, according to researchers, are likely causes of the more encouraging trends in the SAM over a longer period of time.

It's crucial to comprehend the variations between the poles.

Continents surround the Arctic Ocean, which is an ocean. Oceans encircle the continent of the Antarctic.

Ice growth in the Antarctic during the winter is much less constrained due to the geographic divergence. As far north as the conditions will allow, the floes can form.

This explains why the extents are so much greater than in the Arctic, where maximums now hardly ever exceed 15 million square kilometers (5.08 million square miles).

The geography, however, also means that in many locations, summertime warmth can chase the sea ice all the way back to the Antarctic coastline.

And because the Antarctic struggles to maintain ice over the course of a year, its floes are typically much thinner than those in the Arctic, measuring just one meter or less as opposed to three to four meters for long-lived ice in the polar north.

Jana Tauschinski and Becky Dale contributed more reporting.

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