- Lack of atmospheric data makes it difficult to draw conclusions on the potential causes of the current sea-ice developments in the Arctic and Antarctic
- Wet snow and less sea ice in the vicinity of Svalbard: AWI experts forced to cancel their planned thickness measurements on the ice
- No major deviations: At the beginning of winter, the sea-ice extent in the Antarctic matched the level seen in April 2024 and 2025
Missing data: Currently, no temperature or atmospheric pressure data available
For nearly two months now, there has been a major gap in the sea-ice-relevant environmental data available to the Sea Ice Portal: we currently have no access to the temperature and atmospheric pressure reanalysis data from the US-based National Oceanic and Atmospheric Administration (NOAA).
Since the 1990s, the National Centers for Atmospheric Prediction (NCEP) and the National Center for Atmospheric Research (NCAR) have implemented a range of reanalysis projects to generate long-term global datasets on key atmospheric parameters; these datasets were also used by the Sea Ice Portal. Reanalyses are based on models that work similarly to weather-forecasting models and which are supplied with observational data from a range of sources. These include weather stations, ships, aircraft, radiosondes and satellites. Thanks to the consistent use of a uniform calculation model for all sources, the data is particularly well suited to long-term analyses.
In March 2026, the NCEP quit providing the dataset; since then, it hasn’t been updated. Consequently, we can no longer offer our established services regarding air temperatures, atmospheric pressures, wind speeds and sea-ice drift. We are currently exploring alternative data sources.
Moreover, the lack of up-to-date reanalysis data has direct effects on the scientific assessment of current developments: for example, we cannot now conclusively say whether or not April 2026 was markedly warmer or windier than the long-term mean in the polar regions.
The Arctic: A repeat performance of 2016
In April 2026, the Arctic sea-ice extent declined much faster than in April 2025, losing ca. 1.1 million square kilometres in the span of 30 days – from 14.10 million square kilometres on the first day of the month, to 12.97 million square kilometres on the last. The monthly mean value was 13.62 million square kilometres, the fourth-lowest for April in the time series. As such, this year’s mean April sea-ice extent lay precisely on the trend line, confirming the long-term sea-ice decline in the Arctic (Figure 1).
“In April, we had very little sea ice in the Arctic. Especially in the second half of the month, the sea-ice extent curve was clearly below the span of minima and maxima for our reference period, 1981 to 2010,” says Dr Renate Treffeisen, an atmospheric researcher at the Alfred Wegener Institute and expert at the Sea Ice Portal (Figure 2). “And in the first week of May, the situation became even more extreme. At the moment, we have the lowest amount of sea ice ever observed in the Arctic at this time of year, except for once before: the level was similarly low in April and May 2016,” the AWI expert explains.
Figure 1: The monthly mean Arctic sea-ice extent for April 2026 lies exactly on the trend line for the month, confirming the long-term decline in Arctic sea ice.
Figure 2: Development of sea-ice extent in comparison. Especially in the second half of the month, the curve for the year 2026 (sky blue line) was well below the turquoise band, which represents the span of minima and maxima in the period 1981 – 2010.
Predictions of future developments aren’t currently possible: “In the course of May, we’ll see whether, say, storms break up the sea ice or whether cooler air masses slow the sea-ice melting,” says Renate Treffeisen.
In the second half of April, there was a great deal of ice motion, at least north of the Svalbard archipelago. “In this region, the sea-ice concentration is changing on a daily basis. It would even seem that, on 23 and 24 April, the sea ice there was broken up on a large scale or even melted. Due to the lack of atmospheric data, we can’t currently make any statements on atmospheric influences. But in our map of mean sea-surface temperature deviations from the long-term mean, we can see that the surface water in the region was up to 1.5 degrees Celsius warmer than in the reference period. This additional heat could of course have contributed to the sea-ice melting observed,” she explains (Video 1).
Video 1: This series of sea-ice concentration maps for the month of April (from the region north of Svalbard) illustrates how quickly the sea-ice concentration can change within a given area. Particularly in the maps from the fourth week of April, the sudden and wide-scale decline in concentration can be clearly seen. Due to the lack of atmospheric data, unfortunately we cannot draw any conclusions as to the causes.
Figure 3: Mean Arctic sea-surface temperature anomalies in April 2026. Especially in the Arctic regional zones of the North Atlantic, the surface water was 1.5 to 2 degrees Celsius warmer than in the reference period 1971 – 2000. In the Barents Sea and the Svalbard archipelago, these higher temperatures attest to the progressive Atlantification [MF2.1]of the Arctic Ocean.
Figure 4: Difference in the mean position of the ice margin in April 2026, compared to the long-term mean for the years 2003 – 2014. Regions marked in blue had more Arctic sea ice in the fourth month of 2026 than in the reference period; those marked in red had less. The loss of ice cover in southern Svalbard, the southern Greenland Sea, the Barents Sea and Sea of Okhotsk is clearly recognisable.
Svalbard: Extremely wet snow and less sea ice
A few days ago, the team from the AWI’s aerial surveying campaign IceBird returned from their flights in the Arctic with an impression of little sea ice surrounding Svalbard, and of very little snow on its islands. “Of course, it was just a snapshot, but compared to previous years we had so little snow on Svalbard that it barely registered on our snow radar. And colleagues who had planned to supplement our flights with readings taken directly on land and the sea ice had to cancel them, as there wasn’t enough snow for them to reach the survey areas by snowmobile,” recalls AWI sea-ice physicist Luisa Wagner, who led the 2026 IceBird monitoring campaign (Figures 5 & 6).
Figure 5: Approaching the provincial capital Longyearbyen from the air, AWI sea-ice physicist Luisa Wagner and her team could see mountains with large patches of snow-free slopes – an unusual sight for the month of April. Photo: Luisa Wagner / Alfred Wegener Institute
Figure 6: Taken from the research aircraft Polar-6 while flying over Storfjorden, a body of water in southeast Svalbard. At the time, the sea ice was already quite thin, highly mobile, and had very little snow cover. Photo: Luisa Wagner / Alfred Wegener Institute
Does that mean this winter was particularly warm, with little snow in Svalbard? “We had a number of warm phases in December and January, with air temperatures above freezing. On those days, it rained instead of snowing,” reports Dr Marion Maturilli, an AWI atmospheric researcher and head of the Meteorological Observatory at the German and French Arctic research station AWIPEV, located in the research village of Ny-Ålesund on Spitsbergen, Svalbard.
In mid-April, air temperatures then climbed above 6 degrees Celsius, as Norwegian Weather Service data from Ny-Ålesund shows; at this time of year, the temperature should have normally been around minus 8 degrees Celsius. This heat, which was accompanied by ample rain, made the snow cover dwindle extremely rapidly, leaving behind very wet residual snow. In turn, the sodden ground forced Norwegian glaciologists to interrupt their snow-thickness measurements on the glaciers near Ny-Ålesund (you can read the full story here). As such, the AWI sea-ice physicists weren’t the only ones to suffer from the weather conditions.
Fortunately, a team of AWI permafrost experts had considerably better luck. Dr Julia Boike and her colleagues Moritz Rath and Dr Frederieke Miesner, who had come to Ny-Ålesund in early March 2026 for fieldwork on snow and permafrost, could clearly see evidence of the winter rainfall in the snow profiles they collected.
“There were frozen layers in the snow, some of which were so thick and hard that we broke a number of tools collecting the snow profiles. Frozen structures like this form when rain falls on the snow, it melts slightly and then refreezes,” Julia Boike explains (Figures 7, 8 & 9).
Figure 7: Master’s student Moritz Rath kneels in the snow while collecting snow profiles on Spitsbergen. In Ny-Ålesund and the vicinity, the snow cover was roughly 50 to 80 centimetres deep in March 2026[MF5.1] and even up 1.5 metres deep in areas with heavy drifting. Photo: Paul Overduin / Alfred Wegener Institute
Figure 8: Snow profile, frontal view. Here, the snow cover was 67 centimetres deep. The conspicuous square cavities are produced when researchers collect snow samples for more detailed analysis in the lab. Photo: Moritz Rath / Alfred Wegener Institute
Figure 9: Closeup of frozen layers in the snow on Spitsbergen. These structures are created when rain falls on the snow, the snow layer melts, and then refreezes. When this is followed by new snowfall, the ice layer is effectively trapped in the snow profile. Photo: Julia Boike / Alfred Wegener Institute
The Antarctic: No major deviations
In April 2026, roughly just as much new sea ice formed in the Antarctic as in the past two Aprils; the sea-ice development curves for April 2024, 2025 and 2026 are very similar. The monthly mean value was 6.35 million square kilometres, putting it in thirteenth place in the April time series (Figures 10 & 11).
“The consistency of the sea-ice development in 2024, 2025 and 2026 indicates that the sea-ice situation in the Antarctic is currently stable, without any extreme events. But we shouldn’t forget that the monthly mean values for the sea-ice extent are generally well below the trend line,” says Dr Klaus Grosfeld, an AWI climate researcher and co-founder of the Sea Ice Portal.
Figure 10: In April 2026, the sky blue annual curve for Antarctic sea-ice extent was clearly within the turquoise band of minima and maxima in the reference period 1981 – 2010 and nearly matched the curves for 2024 and 2025.
Figure 11: The time series of monthly mean values for the sea-ice extent in April supports two observations. Firstly, the sea-ice extent reached the same level for a third consecutive year. Secondly, it was often well below the trend line.
For a second consecutive month, the formation of new sea ice was sluggish, particularly in the Bellingshausen Sea, the marginal zones of the Weddell Sea, and the western Ross Sea (Figures 12 & 13). However, it’s too soon to speak of a clear trend. “Sea-ice distribution in the Antarctic is subject to substantial fluctuation, even if we’re now seeing certain patterns more often. In the Bellingshausen Sea, for example, the difference in the mean position of the ice margin in April 2026 and in April 2022, 2023 and 2025 indicates far less sea ice than the long-term mean,” Klaus Grosfeld explains.
Figure 12: Difference in the mean position of the ice margin in April 2026, compared to the long-term mean for the years 2003 – 2014. Regions marked in blue had more Antarctic sea ice in the fourth month of 2026 than in the reference period; those marked in red had less.
Figure 13: This overview demonstrates how varied the mean position of the Antarctic ice margin can be. It shows differences in the mean position of the ice margin in April for the years 2021 – 2026, always compared to the long-term mean for the years 2003 – 2014.
Emperor penguins classified as “endangered”
With the emperor penguin, one of the most prominent residents of the Antarctic sea ice is now considered an endangered species. In the course of an evaluation for the Red List of Threatened Species in April 2026, experts from the International Union for Conservation of Nature (IUCN) reclassified the largest penguins in the world – from “near threatened” to “endangered”.
According to an IUCN press release: “Climate change in Antarctica is leading to changes in sea-ice that are projected to cause the emperor penguin population to halve by the 2080s.” As the experts report, satellite images indicate that the emperor penguin population declined by roughly 10 percent from 2009 to 2018 alone – a loss of more than 20,000 adult penguins.
As the IUCN concludes, the main cause of this decline is the early break-up and loss of the sea ice. Emperor penguins are dependent on fast ice – sea ice that is “fastened” to the coastline, seafloor or grounded icebergs – as a habitat for their chicks and during moulting phases, when their feathers aren’t waterproof. When the fast ice breaks up too soon, it can have deadly consequences for the birds (Figure 14).
“[…] human-induced climate change poses the most significant threat to emperor penguins. Early sea-ice break-up in spring is already affecting colonies around the Antarctic, and further changes in sea-ice will continue to affect their breeding, feeding and moulting habitat. Emperor penguins are a sentinel species that tell us about our changing world and how well we are controlling greenhouse gas emissions that lead to climate change,” said Dr Philip Trathan, a member of the IUCN SSC Penguin Specialist Group who worked on the new emperor penguin Red List assessment.
Figure 14: Especially when moulting and when raising their young, emperor penguins need stable fast ice. If the sea-ice cover breaks up and disperses during these times, their chances of survival are slim. Photo: Reinhard Sibberns / Alfred Wegener Institute (CC-BY 4.0)
In addition, the IUCN has now changed the status of the southern elephant seal by two categories – from “least concern” to “vulnerable”. Over the past 25 years, the population of these large marine mammals has declined by more than 50 percent: from an estimated 2.2 million seals in 1999 to only 944,000 in 2025.
The IUCN experts attribute this decline, too, to climate change. The southern elephant seal chiefly feeds on the Antarctic krill. As they report: “[…] rising ocean temperatures and shrinking sea-ice are pushing krill to greater ocean depths in search of colder water, reducing the availability of food for seals.” Moreover, the survival rate for young seals during their first year of life has sunk dramatically, as there are no longer enough krill near the island South Georgia. In turn, the remaining population is ageing. That being said, other risks could also be relevant – like killer whales and leopard seals, which hunt southern elephant seals, or competition for resources with the growing population of baleen whales, which also feed on Antarctic krill.