- Data gap partly remedied: The Sea Ice Portal can once again offer monthly mean-value maps of air temperatures in the Arctic and Antarctic – now on the basis of the global atmospheric reanalysis ERA5, developed by the Europe-based Copernicus Climate Change Service.
- Sea-ice development: In May 2026, the sea-ice extent remained at low to extremely low levels in the Arctic and Antarctic alike.
- New study: The decline in Arctic sea ice has opened the door for dramatic nutrient losses in the ocean. Instead of sunlight, now the availability of nitrate is what limits the productivity of the Arctic Ocean’s ecosystems.
First of all, two pieces of good news
For two different reasons, May 2026 was an exceptionally busy month for the Sea Ice Portal team, and one full of anticipation. We all invested our blood, sweat and tears to make the portal’s first Science Story. Titled “Tracking Down the Stones”, it describes how a team of researchers applied interdisciplinary collaboration to discover a new climatic domino effect in Fram Strait. The multimedia story was released yesterday, at the same time as the corresponding article in the journal Nature. You can check them both out here.
While one part of our team focused on glaciers, icebergs, and stones in the Arctic deep sea, our data manager Dr Annekathrin Jäkel spent a great deal of time securing a new source of reliable atmospheric data from the polar regions. From now on, she will prepare ERA 5 reanalysis data from Europe’s Copernicus Climate Change Service and make it available on the Sea Ice Portal. The service provides a reanalysis dataset that includes both observational and model-based data.
“This March, the US-based NCEP/NCAR Reanalysis 1 data products, which formed the basis for our atmospheric data map products, were discontinued. We have now begun applying programming routines that employ ERA 5 reanalysis data from Europe’s Copernicus Climate Change Service. We’re very pleased that doing so will allow us to successively expand our service,” says Dr Annekathrin Jäkel, who is responsible for the data section of the AWI’s meereisportal.de website. “However, it will take a bit of time before all maps are once again consistently available, as we need to first set up the automatic download for the European data and the data updates aren’t made daily, but with a five-day delay,” the data expert adds.
Figure 1: AWI data expert Dr Annekathrin Jäkel is responsible for data flows and processing at the Sea Ice Portal.
The Arctic: Sea-ice extent at an extremely low level
The atmospheric data from the reanalysis dataset ERA5 will now help us to gain a better understanding of the sea-ice development in the Arctic. But first, let’s talk numbers: in May 2026, satellites detected a decline in Arctic sea-ice extent from 12.91 million square kilometres at the beginning of the month to 11.35 million square kilometres at its end. The curve for the year 2026 was slightly below to markedly below the span of minima and maxima in the years 1981 – 2010.
In May, the monthly mean Arctic sea-ice extent was 12.14 million square kilometres: the second-lowest May mean on record, followed closely by the figures for the years 2019 and 2020. The only lower May sea-ice extent was in 2016 (Figures 2 & 3).
Figure 2: In May 2026, the annual curve almost exactly matched the curves from May 2019 and 2020. This parallelism in sea-ice development was also reflected in the time series of mean sea-ice extents.
Figure 3: The monthly mean Arctic sea-ice extent for May 2026 lay just below the trend line and was virtually identical to the monthly mean for May 2019. Only in May 2016 was there significantly less sea ice at this time of year.
Figure 4: Difference in the mean position of the ice margin in May 2026, compared to the long-term mean for the years 2003 – 2014. Regions marked in blue had more Arctic sea ice in the fifth month of 2026 than in the reference period; those marked in red had less.
In May, the most evident sea-ice retreat compared to the long-term mean (2003 – 2014) could be seen in the northern and southeast Barents Sea, between the archipelagos Svalbard and Franz Josef Land, and in the northwest Denmark Strait, the waters between Greenland and Iceland. Satellites detected more ice compared to the long-term mean in the southern Bering Strait and the eastern margin of the ice stream that flows through Fram Strait and the Greenland Sea (Figure 4).
In the Bering Strait, the unusually low sea-surface temperatures may help to explain why more pack ice survived the month of May than e.g. in the long-term mean (Figure 4). Conversely, the remaining sea ice that had survived the spring likely melted more rapidly in the Barents Sea and between Svalbard and Franz Josef Land due to the sea-surface temperatures and air temperatures, both of which were significantly above the long-term mean (Video 1 & Figure 5).
According to meteorological monitoring data from the German-French Arctic research station AWIPEV on Spitsbergen, the daily high temperatures in Ny-Ålesund were far more often above zero than the researchers were accustomed to seeing at this time of year, particularly in the second half of the month. Moreover, as our temperature anomaly map shows, the air masses at an altitude of ca. 760 metres over Spitsbergen were on average roughly 2 to 3 degrees Celsius warmer than in May of the years 1971 – 2000 (Figure 6).
Figure 5: Mean Arctic sea-surface temperature anomalies in May 2026. Clearly recognisable: the unusually cool water temperatures in the Bering Sea and parts of the Canadian Arctic Archipelago, and up to 2 degrees Celsius higher surface temperatures in the Denmark Strait and Barents Sea.
Video 1: Changes in Arctic sea-ice concentration from 1 – 31 May 2026.
Figure 6: Mean Arctic temperature anomalies in May 2026, compared to the reference period May 1971 – 2000. (Source: see the end of this update)
The Antarctic: Essentially the same sea-ice extent as in 2024 and 2025
In terms of the sea-ice extent, roughly just as much new Antarctic sea ice formed in May 2026 as in the same month of the two previous years (Figure 7). The extent rose from 7.91 to 10.96 million square kilometres – by more than 3 million square kilometres, an area approximately the size of India.
Yet unlike in the record-low year 2023, the curve for the year 2026 was not well below the span of minima and maxima, instead consistently remaining in the bottom third of the span. Nevertheless, with a monthly mean value of 9.49 million square kilometres, the sea-ice extent in May 2026 was ca. 500,000 square kilometres below the trend line (Figure 8). As such, the sea-ice situation in the Antarctic remains tense.
Figure 7: Development of Antarctic sea-ice extent in May 2026. Especially in the first half of the month, the curve for the year 2026 (blue) nearly matched the curves from 2024 (red) and 2025 (violet).
Figure 8: Time series of mean Antarctic sea-ice extent for the month of May. The monthly mean value was at roughly the same level for a third consecutive time, though well below the trend line. In the time series of lowest monthly mean values for May, it is currently in ninth place.
Figure 9: Difference in the mean position of the ice margin in May 2026, compared to the long-term mean for the years 2003 – 2014 (left) and to the ice distribution in May 2025 (right). Regions marked in blue had more Antarctic sea ice in May 2026 than in the reference period; those marked in red had less.
Sea-ice growth was conspicuously slow in the Bellingshausen Sea, eastern Weddell Sea, and off the coast of Queen Maud Land. More ice compared to the long-term mean could only be found in the eastern marginal zones off the coast of West Antarctica and in small areas off the coast of East Antarctica (Figure 9).
In comparison to the previous year, the higher ice levels in the western Weddell Sea, the Ross Sea, and off the coast of Queen Maud Land are particularly evident. Conversely, there was significantly less sea ice off the coast of East Antarctica than in May 2025. Accordingly, the sea-ice distribution in May 2026 differed substantially from that in May 2025, making it more difficult to draw conclusions regarding the possible causes or distribution patterns.
There are, however, a few clues: according to temperature data from the Climate Reanalyzer, the air temperature anomalies at two metres over the Antarctic Peninsula and the eastern Weddell Sea were as much as 10 degrees Celsius on some days in May (Figure 10). In fact, in mid-May the temperature was up to 20 degrees Celsius above the long-term mean for the years 1991 – 2020 over Queen Maud Land (Figure 11). In other words, on that day it was only minus 10 degrees Celsius, not the usual minus 30. At this temperature, the sea’s surface still freezes, though not as quickly as at minus 30 degrees Celsius. These warm spells may have slowed the formation of new ice (Figures 10 & 11).
Needless to say, the effects of such extreme temperatures can also be seen in the mean temperature anomaly statistics. Our monthly air temperature anomaly map for May 2026 shows substantial deviations of 1 – 4 degrees Celsius compared to the reference period May 1971 – 2000, especially over the Weddell Sea and Queen Maud Land (Figure 12).
Figure 10: Air temperature anomalies at two metres above the land and sea surface on 6 May 2026. The red-coloured area over the eastern Weddell Sea represents deviations of up to 10 degrees Celsius. Graphic: Climate Reanalyzer
Figure 11: Air temperature anomalies at two metres above the land and sea surface on 14 May 2026. The red- and bright red-coloured area over Queen Maud Land represents deviations of up to 20 degrees Celsius. Graphic: Climate Reanalyzer
Figure 12: Mean Antarctic temperature anomalies in May 2026, compared to the reference period May 1971 – 2000. (Source: see the end of this update)
A new study shows: When the Arctic sea ice dwindles, the seawater’s nutrient content follows suit
In May, a new study coordinated by researchers at the University of Edinburgh caused quite a stir. According to their observational data, the extensive decline in Arctic sea ice has led to substantially lower nitrate concentrations in the Arctic Ocean. Nitrate is a plant nutrient and essential for the growth of microalgae (phytoplankton), which in turn form the basis of the Arctic food web.
For their study, the experts analysed physical and biochemical field data gathered from polar surface water in Fram Strait that flowed from the Arctic Ocean to the North Atlantic in the period 1998 – 2023. According to their findings, nitrate concentrations in Arctic water masses have steadily declined since 2009. This coincides with a dramatic decline in Arctic sea ice, which began at roughly the same time.
This loss of nitrate is caused by a process referred to by experts as “benthic denitrification”. The process is essentially as follows: due to sea-ice retreat, algal blooms form more often in Arctic waters, as the sunlight can now directly reach the surface water. The algae grow, multiply, die and then sink to the ocean’s depths. On their way to the seafloor, or once having reached it, microbes break the algae down, consuming oxygen in the process. Once the oxygen in the deep water or bottom water has been depleted, certain microbes convert the nitrate into nitrogen gas. The gas is in turn released into the atmosphere, making it unavailable to marine biotic communities. According to the authors, this denitrification is particularly pronounced in the shallow Siberian marginal seas of the Arctic Ocean.
In nutrient-poor waters, only smaller phytoplankton species grow, which are less nutritious for copepods and other species of zooplankton than the original diatoms. And if there are fewer zooplankton available, it spells trouble for fish and other predators. Consequently, this trend could impact fish stocks, seabirds, seals and whales in the North Atlantic and therefore commercial fishing, as the experts conclude.
In their view, the sea-ice retreat and attendant nitrate loss have already fundamentally transformed the Arctic Ocean. Whereas before 2009, sunlight was the limiting factor for biomass production there, it has since been supplanted by the limited availability of nitrate.
Their third main conclusion, presented in a press release to accompany the study, is equally troubling, namely: “Since the change in nutrient conditions is driven by ongoing sea ice loss, it is very unlikely the Arctic Ocean will ever revert to its previous state.” Consequently, further research is needed in order to determine the farther-reaching effects that these changes in the waters of the Arctic could have on marine organisms in other parts of the globe, including the North Atlantic.
The US Pacific coast: Rising number of grey whale deaths
Given these new insights into the changing Arctic, it’s hardly surprising that once again, an unusually large number of grey whales died on the Pacific coast of North America in the spring of 2026. On 25 May 2026, the US network NBC News reported that, in the span of three months, 21 grey whales had washed up dead on the coast of Washington. Experts attribute this unusually high mortality rate to the sea-ice decline in the Bering Sea and resultant changes in the ecosystem; the whales can no longer find enough food.
The cadavers of the dead whales appeared to be weak and malnourished. Some clearly displayed orientation problems before dying, possibly because of their poor health. As of the time of this sea-ice update’s publishing, the number of stranded whales had climbed to 30. The Cascadia Research Collective has set itself the task of documenting these strandings. You can find the list here.
Video 2: Televised news coverage from the station FOX 13 Seattle on the grey whale strandings in the state of Washington.
Information Copernicus ERA5 Daten
Guidelines: In addition to the requirements of the applicable license(s), users must: cite the CDS catalogue entry; provide clear and visible attribution to the Copernicus programme and attribute each data product used; Citing the CDS catalogue entry. Copernicus Climate Change Service (2023): ERA5 monthly averaged data on pressure levels from 1940 to present. Copernicus Climate Change Service (C3S) Climate Data Store (CDS). DOI: 10.24381/cds.6860a573 (Accessed on 08-06-2026)
Attribution
Copernicus programme: Generated using or contains modified Copernicus Climate Change Service information 08-06-2026. Neither the European Commission nor ECMWF is responsible for any use that may be made of the Copernicus information or data it contains. Citing the data: Hersbach, H., Bell, B., Berrisford, P., Biavati, G., Horányi, A., Muñoz Sabater, J., Nicolas, J., Peubey, C., Radu, R., Rozum, I., Schepers, D., Simmons, A., Soci, C., Dee, D., Thépaut, J-N. (2023): ERA5 monthly averaged data on pressure levels from 1940 to present. Copernicus Climate Change Service (C3S) Climate Data Store (CDS), DOI: 10.24381/cds.6860a573 (Accessed on 08-06-2026)