Arctic sea ice
The image below, adapted from the Danish Meteorological Institute, shows that Arctic sea ice volume was at a record low for the time of year on April 20, 2026.
The image below, adapted from the Danish Meteorological Institute, shows that Arctic sea ice volume was at a record low for the time of year on April 20, 2026.
 |
| [ click on images to enlarge ] |
End April 2025, an Arctic sea ice maximum volume was reached of about 19,000 km³, as highlighted by the image on the right. The 2026 maximum may turn out to be even lower, about 18,000 km³.
That 18,000 km³ is an important number. The image below shows Arctic sea ice volume through April 18, 2026, with the strength of the melting between April (annual maximum, blue) and September (annual minimum, red) indicated by bars colored magenta (strong melting, 18,000 km³) and green (little melting, 15,000 km³).
A record low maximum volume was reached in April 2025. Relatively little melting took place from April 2025 to September 2025, yet a record low minimum volume was reached in September 2025. The April 2026 maximum looks set to be even lower, i.e. about 18,000 km³.
In the above image, the difference between strong melting (magenta) and little melting (green) is 3000 km³. With strong melting taking place from April 2026, this may well cause a Blue Ocean Event to occur, with virtually all Arctic sea disappearing in September 2026.
In the above image, the difference between strong melting (magenta) and little melting (green) is 3000 km³. With strong melting taking place from April 2026, this may well cause a Blue Ocean Event to occur, with virtually all Arctic sea disappearing in September 2026.
Methane threat
The image below, from an earlier post, illustrates the threat of thinning of Arctic sea ice resulting in increased ocean heat and methane eruptions. Arctic sea ice decline could strongly contribute to the temperature rise, as illustrated by the image below and also discussed in this earlier post.
 |
| [ The Buffer is gone ] |
Temperature
Recently, the 2026 SST was just short of the record high SST of 21.17°C reached in 2024. The 2026 SST has risen strongly and keeps rising, even as the average anomaly for earlier years is coming down due to the change of seasons that is causing SST to come down in the Southern Hemisphere where most of the world oceans are located.
In the Southern Hemisphere, the surface air temperature remains at a record high for the time of year, as illustrated by the image below that shows SH temperatures through April 14, 2026.
What makes the situation particularly dangerous is that an El Niño is on the way that may be very strong and that may peak in December 2026. El Niño is named after the Spanish phrase "El Niño de Navidad," meaning "the Christ Child" or "the little boy," as South American fishermen in the 1800s noticed that the unusually warm ocean waters—which reduced their fish catch—tended to peak around Christmas time.
With high SST in the Southern Ocean in December 2026, Antarctic sea ice will undergo very strong melting, threatening an Antarctic Blue Ocean Event to occur early 2027.
The higher the water's salt content, the lower its melting point. Seawater typically has a salinity of about 3.5% (35 grams of salt per liter of water). Sea ice starts melting when the temperature rises to about -2°C (28.4°F). By contrast, freshwater remains frozen as long as the temperature remains below 0°C (32°F).
A recent study led by Theo Spira finds that, in 2015, anomalously strong winds enhanced mixing across the thin Winter Water layer, entraining warm and salty subsurface waters, which broke down upper-ocean stratification. Another recent study led by Earle Wilson find that in 2015, intensified wind-driven upwelling reversed the freshening trends, releasing years of accumulated ocean heat that contributed to unprecedented sea ice loss.
An earlier post discusses a study led by Alessandro Silvano that finds how, around 2015, surface salinity in the Southern Ocean began rising sharply – just as sea ice extent started to crash. The post describes that higher temperatures come with feedbacks such as stronger wind and stronger evaporation, resulting in increased water vapor in the atmosphere. Much of the water vapor will return to the surface in the form of precipitation such as rain and snow, but part of this precipitation will fall over Antarctica, with the net result of an increase in salinity of surface of the Southern Ocean. The post also points at the danger that heat, previously stored in the deep ocean by sinking circumpolar waters, will instead remain at the surface and cause atmospheric temperatures to rise.
Could what happened in 2023 happen again? An earlier post describes how the upcoming El Niño could cause dramatic loss of Arctic sea ice and further emissions that could jointly increase global temperatures and contribute to an Antarctic sea ice decline even stronger than in 2023.
In conclusion, An Arctic Blue Ocean Event could occur in September 2026, followed by an Antarctic Blue Ocean Event in early 2027.
• Kevin Pluck - Sea ice visuals
https://seaice.visuals.earth
• Climate Reanalyzer
https://climatereanalyzer.org
• Wind-triggered Antarctic sea-ice decline preconditioned by thinning Winter - by Theo Spira et al. Waterhttps://www.nature.com/articles/s41558-026-02601-4
The world (60°S–60°N, 0–360°E) sea surface temperature (SST) was at a record high for the time of year on April 19, 2026, as illustrated by the image below.
What makes the situation particularly dangerous is that an El Niño is on the way that may be very strong and that may peak in December 2026. El Niño is named after the Spanish phrase "El Niño de Navidad," meaning "the Christ Child" or "the little boy," as South American fishermen in the 1800s noticed that the unusually warm ocean waters—which reduced their fish catch—tended to peak around Christmas time.
With high SST in the Southern Ocean in December 2026, Antarctic sea ice will undergo very strong melting, threatening an Antarctic Blue Ocean Event to occur early 2027.
Antarctic sea ice
Could an Antarctic Blue Ocean Event occur in early 2027? As illustrated by the image below, Antarctic sea ice area was only 1.09 million km² on February 22, 2023, very close to the 1 million km² threshold when a Blue Ocean Event could be called.
 |
| [ Saltier water, less sea ice - from earlier post ] |
What caused the 2023 Antarctic sea ice decline? Until 2015, rising temperatures resulted in melting of ice and enhanced precipitation that freshened the surface of the Southern Ocean, exacerbated by increasing stratification that prevented mixing. The temperature rise over the years also caused winds to be stronger, at the time causing the sea ice to spread out wider.
The higher the water's salt content, the lower its melting point. Seawater typically has a salinity of about 3.5% (35 grams of salt per liter of water). Sea ice starts melting when the temperature rises to about -2°C (28.4°F). By contrast, freshwater remains frozen as long as the temperature remains below 0°C (32°F).
A recent study led by Theo Spira finds that, in 2015, anomalously strong winds enhanced mixing across the thin Winter Water layer, entraining warm and salty subsurface waters, which broke down upper-ocean stratification. Another recent study led by Earle Wilson find that in 2015, intensified wind-driven upwelling reversed the freshening trends, releasing years of accumulated ocean heat that contributed to unprecedented sea ice loss.
An earlier post discusses a study led by Alessandro Silvano that finds how, around 2015, surface salinity in the Southern Ocean began rising sharply – just as sea ice extent started to crash. The post describes that higher temperatures come with feedbacks such as stronger wind and stronger evaporation, resulting in increased water vapor in the atmosphere. Much of the water vapor will return to the surface in the form of precipitation such as rain and snow, but part of this precipitation will fall over Antarctica, with the net result of an increase in salinity of surface of the Southern Ocean. The post also points at the danger that heat, previously stored in the deep ocean by sinking circumpolar waters, will instead remain at the surface and cause atmospheric temperatures to rise.
Could what happened in 2023 happen again? An earlier post describes how the upcoming El Niño could cause dramatic loss of Arctic sea ice and further emissions that could jointly increase global temperatures and contribute to an Antarctic sea ice decline even stronger than in 2023.
Conclusion
In conclusion, An Arctic Blue Ocean Event could occur in September 2026, followed by an Antarctic Blue Ocean Event in early 2027.
Climate Emergency Declaration
The feedbacks map below is adapted from an image by Peter Carter, Climate Emergency Institute.
 |
| [ click on images to enlarge ] |
The situation is dire and unacceptably dangerous, and the precautionary principle necessitates rapid, comprehensive and effective action to reduce the damage and to improve the outlook, where needed in combination with a Climate Emergency Declaration, as described in posts such as in this 2022 post and this 2025 post, and as discussed in the Climate Plan group.
Links
• Danish Meteorological Institute - Arctic sea ice volume and thickness
https://ocean.dmi.dk/arctic/icethickness/thk.uk.php
https://ocean.dmi.dk/arctic/icethickness/thk.uk.php
• Kevin Pluck - Sea ice visuals
https://seaice.visuals.earth
• Climate Reanalyzer
https://climatereanalyzer.org
• Wind-triggered Antarctic sea-ice decline preconditioned by thinning Winter - by Theo Spira et al. Waterhttps://www.nature.com/articles/s41558-026-02601-4
discussed on facebook at:
https://www.facebook.com/groups/arcticnews/posts/10164023607639679
• Recent extremes in Antarctic sea ice extent modulated by ocean heat ventilation - by Earle Wilson et al. https://www.pnas.org/doi/10.1073/pnas.2530832123
discussed on facebook at:
https://www.facebook.com/groups/arcticnews/posts/10164149040674679
• Peter Carter - Climate Emergency Institute
https://www.climateemergencyinstitute.com
https://www.facebook.com/groups/arcticnews/posts/10164023607639679
• Recent extremes in Antarctic sea ice extent modulated by ocean heat ventilation - by Earle Wilson et al. https://www.pnas.org/doi/10.1073/pnas.2530832123
discussed on facebook at:
https://www.facebook.com/groups/arcticnews/posts/10164149040674679
• Peter Carter - Climate Emergency Institute
https://www.climateemergencyinstitute.com
• Climate Plan
https://arctic-news.blogspot.com/p/climateplan.html
https://arctic-news.blogspot.com/p/climateplan.html
• Climate Emergency Declaration
https://arctic-news.blogspot.com/p/climate-emergency-declaration.html
https://arctic-news.blogspot.com/p/climate-emergency-declaration.html
