Wednesday, September 24, 2025

Focus on Antarctica

The Antarctic sea ice area was 1.27 million km² below the 1981-2010 mean on September 23, 2025, a deviation from 1981-2010 of -3.05σ, as illustrated by the image below.


This is far below what the Antarctic sea ice area was in 1981-2010. If the situation gets worse over the next few months, an Antarctic Blue Ocean Event may well occur early 2026. In 2023, the Antarctic sea ice was very close to a Blue Ocean Event, with an area of only 1.09 million km² left on February 22, 2023, a deviation of -3.03σ, as illustrated by the image below.

[ image from earlier post, click to enlarge ]
The image below shows the Antarctic sea ice thickness on September 23, 2025. 


The image below shows the Antarctic sea ice concentration on September 23, 2025. 


Earth's energy imbalance

Temperatures keep rising as Earth's energy imbalance keeps rising, which results from a combination of high (and rising) levels of pollution (including concentrations of greenhouse gases, other gases and warming aerosols) and loss of Earth's albedo (reflectivity). Furthermore, rising temperatures come with feedbacks that can speed up acceleration of the temperature rise. 

The image below, by Eliot Jacobson, shows Earth's Energy Imbalance through July 2025 (12-month running mean). 


Albedo loss over the years is illustrated by the graph below, by Eliot Jacobson (based on data through July 2025, 36-month running average). 


Albedo loss results from a decrease in cooling aerosols and from certain feedbacks that are kicking in with increasing ferocity as temperatures rise, including less lower clouds and decline of the snow and ice cover. With the temperature rise also come further feedbacks such as more water vapor in the atmosphere and more extreme weather events that can cause deforestation and associated reductions in cooling aerosols, as illustrated by the Danger Diagram below. 


Many feedbacks are self-amplifying and can also amplify other feedbacks, further speeding up acceleration of the temperature rise, as illustrated by the image below. 

[ from earlier post ]
El Niño 2026 prospect

Furthermore, a new El Niño may emerge soon. El Niño-Southern Oscillation (ENSO) is a climate pattern that fluctuates from El Niño to La Niña conditions and back. El Niño raises temperatures, whereas La Niña suppresses temperatures. This year, there have been neutral to borderline La Niña conditions, as illustrated by the image below, which shows the rises and falls of the sea surface temperature in Niño 3.4, an area in the Pacific (inset) that is critical to the development of El Niño. 


On September 27, 2025, the temperature reached an anomaly in this area of -0.67°C versus 1991-2020. The inset on the above image shows the Niño 3.4 area and the sea surface temperature anomaly versus 1991-2020 that day. The low temperatures in Niño 3.4 over the past few months indicate that La Niña conditions will likely dominate in the remainder of 2025, which implies suppression of the 2025 global temperatures.

A strong La Niña could spell bad news for Antarctic sea ice. A recent study led by Shaoyin Wang shows that the triple-dip La Niña event during 2021–2023 played a major role in record low February Antarctic sea ice extent reached in 2022 and 2023, while the Antarctic ice sheet experienced a transient mass gain rebound.

As also described in earlier posts such as this one and this one, more water evaporates from the Southern Ocean and part of it falls on the Antarctic ice sheet, thickening the snow layer. As a result, the Southern Ocean surface is getting more salty. Saltier surface waters sink more readily, allowing heat from the deep to rise, which can melt Antarctic sea ice from below, even during winter, making it harder for ice to reform. This vertical circulation also draws up more salt from deeper layers, reinforcing the cycle.

[ image from earlier post ]
On the other hand, a new El Niño may emerge soon. The image on the right, adapted from ECMWF, shows an ENSO forecast for developments in Niño3.4 through August 2026, indicating that the next El Niño may emerge in 2026 and grow in strength in the course of 2026.

In conclusion, an Antarctic Blue Ocean Event may occur early 2026 and this could be followed by an Arctic Blue Ocean Event later in 2026, in particular if a strong El Niño will emerge in the course of 2026 and further feedbacks are triggered, such as seafloor methane eruptions. 

Why a Blue Ocean Event is so dangerous

[ from earlier post ]
PIOMAS estimates that 16,400 km³ of ice is lost every year (1979-2010 average) from April to September, consuming an amount of energy of 5 x 10²¹ Joules (the image on the right shows calculations, click on this link or on the image to enlarge).

Once the latent heat buffer is lost, further heat must go elsewhere. During the phase change from ice to water, the temperature doesn't rise, i.e. all the energy goes into the process of changing ice into water. Once all ice has melted, further heat will raise the temperature of the water. The amount of energy that is consumed in the process of melting the ice is as much as it takes to heat an equivalent mass of water from zero°C to 80°C. 


Decline of the snow and ice cover comes with numerous feedbacks, the loss of the latent heat buffer (feedback #14 on the feedbacks page) is only one of them. Further feedbacks include the loss of albedo (feedback #1), increases in emissions (feedback #2), loss of emissivity (feedback #23), while there are also changes to the Jet Stream (feedback #14) and changes to clouds and water vapor (feedback #20), and there are mechanisms and circumstances aggravating the danger, such as the slowdown of AMOC and further changes to ocean currents.

[ The Buffer is gone, from Accelerating Temperature Rise ]
Sea ice constitutes a buffer that previously consumed much incoming ocean heat (left); as sea ice thins, the buffer disappears while more heat also enters the Arctic Ocean (right). Further heat entering the Arctic Ocean from the Atlantic Ocean and the Pacific Ocean threatens to destabilize sediments that contain methane, causing eruption of huge amounts of methane.

Eruption of methane from the seafloor of the Arctic Ocean (feedback #16) is one of the most dangerous feedbacks. As the seafloor of the Arctic Ocean heats up, heat can penetrate sediments and cause destabilization of hydrates, resulting in eruption of methane. As the seas in the Arctic Ocean can be very shallow, the methane can erupt with force in the form of plumes, with little opportunity for the methane to get decomposed in the water. Furthermore, there is very little hydroxyl in the air over the Arctic, which extends the lifetime of methane over the Arctic.

Ominously, the sea surface temperature anomaly versus 1951-1980 in the north mid latitudes (inset) reached a record monthly high of 1.657°C in August 2025, as illustrated by the image below.


Meanwhile, the Arctic sea ice remains at a record low daily volume, as it has been for more than a year.  

The methane danger is also illustrated by the image below, adapted from an image issued by NOAA September 29, 2025, showing hourly methane averages recorded at the Barrow Atmospheric Baseline Observatory (BRW), a NOAA facility located near Utqiaġvik (formerly Barrow), Alaska, at 71.32 degrees North. 


The image below shows methane concentrations as high as 2622 parts per billion (ppb) recorded by the NOAA 20 satellite on September 30, 2025 am, at 399.1 mb. Note the high methane concentrations over the Arctic, over Antarctica and over the Antarctic sea ice.


Climate Emergency Declaration

UN secretary-general António Guterres recently spoke about the need for “a credible global response plan to get us on track” regarding the international goal of limiting the global temperature rise. “The science demands action, the law commands it,” Guterres said, in reference to a recent international court of justice ruling. “The economics compel it and people are calling for it.” 

What could be added is that 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 this 2022 post and this one and as discussed in the Climate Plan group.


Links

• Kevin Pluck - Sea ice visuals
https://seaice.visuals.earth

• University of Bremen - sea ice concentration and thickness
https://seaice.uni-bremen.de/start

• NOAA - Global Monitoring Laboratory - Data Visualisation - flask and station methane measurements
https://gml.noaa.gov/dv/iadv

• Record high increase in carbon dioxide
https://arctic-news.blogspot.com/2025/04/record-high-increase-in-carbon-dioxide.html

• Double Blue Ocean Event 2026?
https://arctic-news.blogspot.com/2025/09/double-blue-ocean-event-2026.html

• Strong impact of the rare three-year La Niña event on Antarctic surface climate changes in 2021–2023 - by Shaoyin Wang et al.
https://www.nature.com/articles/s41612-025-01066-0

• Extreme Heat Risk
https://arctic-news.blogspot.com/2025/08/extreme-heat-risk.html

• Saltier water, less sea ice 




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