Antarctic sea ice winter peak in 2025 is third smallest on file

Antarctic sea ice has recorded its third-smallest winter peak extent since satellite tv for pc information started 47 years in the past, new information reveals.

Provisional data from the US National Snow and Ice Data Center (NSIDC) reveals that Antarctic sea ice reached a winter most of 17.81m sq. kilometres (km2) on 17 September.

This is 900,000km2 beneath the 1981-2010 common most extent – the historic baseline towards which newer sea ice extent is usually in contrast. 

According to at least one knowledgeable, the “lengthening trend of lower Antarctic sea ice poses real concerns regarding stability and melting of the ice sheet”.

Meanwhile, on the Earth’s different pole, Arctic sea ice reached its annual minimum on 10 September, rating because the joint-Tenth lowest within the satellite tv for pc file.

At 1.6m km2, the 2025 minimal shares the spot with 2008 and 2010. The NSIDC notes that every one 19 of the bottom sea ice extents within the file have occurred up to now 19 years.

Antarctic peak

For a long time, scientists have been utilizing satellite tv for pc information to trace the annual cycle of sea ice progress and soften on the world’s poles. This is a key solution to monitor the “health” of sea ice in each the Arctic and Antarctic.

The map beneath reveals Antarctic sea ice on the day of its most extent for the 12 months on 17 September 2025, the place the yellow line reveals the 1981-2010 common.

The NSIDC says that sea ice extent was “markedly below average” within the Indian Ocean and the Bellingshausen Sea, however “slightly above average” over the Ross Sea.

In an NSIDC press launch saying the Antarctic most, Dr Ted Scambos, a senior analysis scientist on the Cooperative Institute for Research In Environmental Sciences, stated:

“The lengthening trend of lower Antarctic sea ice poses real concerns regarding stability and melting of the ice sheet. However, it may also be leading to greater snowfall over the continent, which would slow the progression of sea level rise.”

Antarctic sea ice progress

In its typical annual cycle, Antarctic sea ice grows throughout winter in direction of its annual most extent in September or October. It then melts all through the spring and summer time in direction of its March minimal.

Earlier this 12 months, Antarctic sea ice recorded its second-smallest summer time minimal on file.

At 1.98m m2, this was the fourth consecutive 12 months that Antarctic sea ice had fallen beneath 2m km2, the NSIDC famous.

In its month-to-month sea ice updates, the NSIDC reported that sea ice then grew at a “near-average pace”. During this era, sea ice “expanded rapidly” within the final areas to lose ice, together with the Ross Sea and japanese Weddell Sea, it stated.

The NSIDC defined that sea ice rebounded rapidly within the Ross Sea space as a result of ice extent had retreated “slowly” there the month earlier than – which means that the higher ocean layer didn’t have time to build up warmth which might gradual the winter freeze.

In April, “the situation in the Antarctic remained fickle”, the NSIDC stated. At the start of the month, sea ice extent neared “record-low” every day extents, however because the month progressed ice cowl expanded “fairly quickly”, it stated.

May had “below average growth” in Antarctic sea ice and noticed the fifth lowest file for Antarctic sea extent.

As June started, the the Bellingshausen Sea and japanese Queen Maud Lord areas have been “far behind” in ice re-growth, it stated, including that the Bellingshausen Sea was nearly completely ice-free as temperatures have been 6-8C above common.

In June, Antarctic sea ice was 1.28m km2 beneath the 1981-2010 baseline, with “particularly low” sea ice extent within the Bellingshausen Sea and the Indian Ocean sector, in response to the NSIDC. This was the third-lowest sea ice extent ever recorded for the month of June, it stated. 

Throughout July, Antarctic sea ice extent grew at a “slower-than-average” fee, in response to the NSIDC. By the top of the month, Antarctic sea ice extent was 1.3m km2 beneath the baseline, it famous.

Arctic soften season

In the Arctic, sea ice cowl usually reaches its excessive level in March, earlier than dropping to its September minimal on the finish of the northern-hemisphere summer time.

The 2025 Arctic sea ice winter peak was the smallest since satellite tv for pc information started. The peak, recorded on 22 March, was 1.31m km2 beneath the typical most for the 1981-2010 historic baseline.

In March, Arctic sea ice extent averaged 14.14m km2 – the bottom within the satellite tv for pc file, in response to the NSIDC. It famous that, on the time,  common air temperature was above the historic baseline throughout a lot of the Arctic area. 

Arctic sea ice extent then “changed very little” all through April, remaining “nearly constant” till the ultimate days of the month, the NSIDC reported.

It added that the ultimate days of April noticed Arctic sea ice extent drop because of ice retreat alongside the coast of the Barents Sea.

According to information, the primary cause why the April complete extent remained largely flat was because of a rise of sea ice within the northeastern Barents Seas that “offset” losses elsewhere.

Below-average air temperatures over the northern Norwegian and Barents Seas was essentially the most “notable feature” of April 2025, the NSIDC stated.

May was marked by a decline in Arctic sea ice extent at a faster-than-average tempo, the NSIDC famous,  ensuing within the seventh-lowest May extent on file. 

It added that ice loss in May was “primarily” within the Barents Sea, Bering Sea and the Sea of Okhotsk.

In June, Arctic sea ice extent averaged 10.48m km2 – the second-lowest common on file for the month, the NSIDC stated. It famous that sea ice hit record-low ranges over 20 June and 26 June and tracked at “near-record” low ranges by means of the month. The Barents and Kara Seas have been each “nearly ice-free” by the top June.

Hudson Bay ice extent was additionally “considerably below average” all through June and northern components of Baffin Bay have been practically ice-free, it stated.

By the top of July, every day sea ice extent within the Arctic had fallen to 7.66m km2 – the third lowest within the satellite tv for pc file, the NSIDC reported. It famous that, for a lot of the month, Arctic sea ice extent tracked near ranges recorded for 2012 – the 12 months by which Arctic sea ice extent reached its lowest-ever September minimal.

Throughout August, the NSIDC reported that sea ice “rapidly melted and compacted” north of Alaska within the Beaufort Sea, with sea ice extent averaging at 5.41m km2 – the seventh lowest on file. 

Dr Zack Labe – a local weather scientist at Climate Central – tells Carbon Brief that northern Siberia noticed August air temperatures greater than 5C above the 1981-2010 common, leading to “a striking amount of open water along the Atlantic side of the Arctic that would normally be ice-covered”.

At an annual minimal of 1.6m km2, this 12 months’s Arctic minimal is “pretty unremarkable”, Labe tells Carbon Brief, and “adds to the evidence of a clear slowdown in the rate of summer Arctic sea ice loss”.

However, Labe stresses that that is “not surprising” – referencing a latest examine which “clearly shows how internal variability can temporarily drive periods of slower melt in a warming climate, as well as periods of rapid melt, such as in the early 2000s”. (For extra on this analysis, learn Carbon Brief’s visitor publish).

He provides:

“It is just a matter of time earlier than summertime soften accelerates once more. This shouldn’t be a excellent news story, particularly since in lots of different months we nonetheless see a transparent downward development…

“While the past decade of summers may give the appearance of a slowdown, regional extremes such as in the Kara Sea this year underscore that the Arctic is already radically different from past decades. The driver is clear – human-caused climate change.”

Satellite change

For a long time, NSIDC has tracked sea ice utilizing information from climate satellites run by the US Navy. However, earlier this 12 months, Mongabay reported that NSIDC scientists “noticed holes in the data they were receiving”.

The article explains:

“When scientists inquired with the Department of Defense (DoD), they were told not all data were being downloaded and access to the data had been deprioritised. Soon after, the DoD said it would stop sharing…data altogether, citing military cybersecurity risks in the old systems.”

NSIDC scientist Walt Meier advised Science that whereas the US satellites “are up there and functioning…we’re not getting all the data anymore, at least regularly”.

The DoD then set a cut-off date to “cease distribution data from the Defense Meteorological Satellite Programme” on 31 July.

In June, the NSIDC announced that it will “explore switching to a different sensor” aboard a Japanese satellite tv for pc that was launched in 2012.

The solely different possibility out there to NSIDC was a “series of Chinese weather satellites, which the country is already using to produce its own record of sea ice”, Science famous. It added {that a} new US DoD climate satellite tv for pc, launched final 12 months, is “also capable of collecting similar data, but its data have not yet been made public”.

The change was accomplished by the July closing date and NSIDC reprocessed all information for 2025 to make use of the brand new information supply to make sure “consistency through the year”.