After the summer minimum in the Antarctic, sea-ice growth rebounding sluggishly
On 31 March 2024, the Antarctic sea-ice extent, at 4.52 million square kilometres, reached its maximum for the month of March and has been on the rise after reaching the annual minimum on 17 February. In the first ten days of the month, the growth rate was ca. 66,000 square kilometres per day, before flagging considerably at mid-month and rallying to an average of 93,000 square kilometres per day in the final ten days. The ice extent at the end of the month was only slightly above that from 2023, a record-breaking year for minimum sea-ice extent (Figure 1).
The monthly mean sea-ice extent in March was 3.46 million square kilometres, making it the eight lowest since the beginning of continuous satellite observation. In direct comparison, that’s roughly 520,000 square kilometres more than in March 2017, the year with the lowest sea-ice extent between 1979 and 2024 (Figure 2).
Accordingly, the sea-ice cover in the Antarctic is below the long-term mean for the years 1981 – 2010 (see interactive graphic, link in the margin) for a third consecutive year. Currently, researchers can’t conclusively say whether or not this represents a permanent change in the sea-ice situation resulting from climate change, or if this development is part of natural climate fluctuations. Below-average sea-ice cover was observed in the years 2017 – 2019, though this trend was interrupted by an above-average sea-ice extent in 2021. Generally speaking, below-average sea-ice extent in comparison to the long-term trend has been observed in every month of the year since 2016 (except in the years 2020 and 2021). To date, research has not yielded a conclusive answer to the question of how the atmosphere and ocean influence sea-ice extent fluctuations in detail. However, in the past decade, extreme temperatures and changed wind patterns have contributed to substantially reduced ice extents. In March, the air temperature at 925 hPa over Central Antarctica and in broad expanses of West Antarctica was up to 6 degrees Celsius above the long-term climatological mean for the years 1971 – 2000; the Ross Sea was also characterised by significantly higher air temperatures (Figure 3).
A study conducted by Purich & Doddridge (2023) determined that atmospheric changes alone couldn’t explain the changes in the sea-ice extent. Fluctuations in temperature and salinity, and the resulting layering of the Southern Ocean, also affect sea-ice growth, as does the increasing meltwater input from melting ice shelves. Assessing the complex interplay of these factors is extremely difficult and can only be achieved by combining coupled climate models, satellite data, and in situ observations of sea-ice physics.
Sea-ice extent in the Arctic
After reaching a previous maximum on 27 February and dropping ca. 270,000 square kilometres by 2 March, the sea-ice extent in the Arctic had grown significantly by mid-March, reaching its maximum for this year – 15.19 million square kilometres – on 19 March (Figure 4). The monthly mean sea-ice extent was 14.95 million square kilometres (Figure 5), the sixteenth lowest since the beginning of satellite observation in 1979.
The ice growth period ended with nearly average sea-ice cover in Baffin Bay and the Bering Sea, above-average cover in the northern Sea of Okhotsk and Greenland Sea, and below-average cover in the Barents Sea. In the Gulf of Saint Lawrence and southern Sea of Okhotsk, the extent was significantly below average (Figure 6).
Atmospheric researchers link ice loss in the Arctic to intense El Niño events
El Niño – a weather phenomenon observed in the Equatorial Pacific that occurs roughly every four years and is triggered by changed oceanic-meteorological flow patterns, in which warm water in the eastern Pacific produces warmer weather conditions – is gradually subsiding. Since last summer, it has contributed to record high temperatures and heavy precipitation around the globe and has intensified global climate warming.
In a recently released study, Deng & Dai (2024) show that these El Niño-associated events could be intensified further by the melting Arctic sea ice. By combining climate model-based simulations and observational data, the experts determined that, due to the current interplay between the Arctic sea ice and atmosphere, the intensity of El Niño events is 12 % to 17 % lower than it would be without this interplay. Since the late 1970s, the amount of sea ice that survives at least one Arctic summer has declined by 12.2 % per decade, and forecasts indicate that the Arctic could see its first ice-free summer by 2040. Consequently, climate models predict a stronger El Niño in the decades to come as a result of global warming.
Previous research into the causes of Arctic amplification – a term that refers to the warming rates in the Arctic, which are three to four times as high as in the rest of the world – supports these findings. In 2022, Deng & Dai released a study that showed how fluctuations in Arctic sea-ice cover affected surface temperatures in the Atlantic.
The most important finding from these publications: The decline in Arctic sea ice has far-reaching effects on the global climate. These effects must be investigated further in order to fully grasp the consequences of global warming-related sea-ice loss. Further, they show that a substantial reduction in global warming is the only way to stop this vicious cycle.
Would you like to make your own visualization of the critical ice loss in the Antarctic? Then try out our new tool, which allows you to create your own animations of the sea-ice concentration for a period of your choosing!
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