Antarctic sea ice

It peaks (~18 × 10^6 km2) during September (comparable to the surface area of Pluto), which marks the end of austral winter, and retreats to a minimum (~3 × 10^6 km2) in February.

[4] Since the ocean off the Antarctic coast usually is much warmer than the air above it, the extent of the sea ice is largely controlled by the winds and currents that push it northwards.

[8]: 7  IPCC AR5 also concluded that the lack of data precludes determining the trend in total volume or mass of the sea ice.

Atmospheric and oceanic drivers likely have contributed to the formation of regionally varying trends in Antarctic sea-ice extent.

[14] Observed autumn and spring trends in the number of extratropical cyclones, anticyclones and blocks, which have a strong thermodynamic control through temperature advection, and a strong dynamic control through ice-drift, on sea-ice extent during the same and also during following seasons are almost everywhere around Antarctica in agreement with the observed, regionally varying, trends in sea-ice extent.

[12] Consequently, the near-surface winds steered around weather systems are thought to explain large parts of the inhomogeneous Antarctica sea-ice trends.

The 2021 IPCC AR6 report confirms the observed increasing trend in the mean Antarctic sea ice area over the period from 1979 to 2014 but assesses that there was a decline after 2014, with the least extent reached in 2017, and a following growth.

[15] The report then concludes that there is “high confidence” that there is no significant trend in the satellite observed Antarctic sea ice area from 1979 to 2020 in both winter and summer.

[T]he greatest part of this southern continent (supposing there is one), must lie within the polar circle, where the sea is so pestered with ice, that the land is thereby inaccessible.