Record-low Antarctic sea ice can be explained by wind patterns and predicted months in advance

Amid all the changes in Earth’s climate, the stormy Southern Ocean sea ice surrounding Antarctica has long been a strange exception. Despite rising global temperatures, the maximum extent of winter sea ice remained the same or increased slightly from the late 1970s to 2015.

That started to change in 2016. After several years of decline, it reached an all-time low in 2023, more than five standard deviations below the average satellite record. The area of ​​sea ice is 2.2 million square kilometers less than the average satellite record and nearly 12 times the area of ​​Washington state. The most recent winter high recorded in September 2024 was very close to the previous year’s low.

Researchers at the University of Washington found that the record low can be explained by warm Southern Ocean conditions and wind patterns that orbited Antarctica months in advance, allowing them to predict the extent of sea ice around Antarctica more than six months in advance. Showed. . This has the potential to support regional and global weather and climate models.

The open-access study was published Nov. 20 in Communications Earth & Environmental.

“Since 2015, the total area of ​​Antarctic sea ice has decreased dramatically,” said lead author Zach Espinosa, a doctoral student in the Department of Atmospheric and Climate Sciences at Wisconsin. “State-of-the-art sea ice forecasting methods generally struggle to produce reliable forecasts with such long lead times. It has been shown to have considerable predictability.

The authors used global climate models to simulate how ocean and air temperatures, including long-term cycles such as El Niño and La Niña, affect sea ice in the Southern Ocean.

The results showed that the 2023 El Niño event will not be as important as previously thought. Rather, regional wind arching patterns and their effects on sea temperatures up to six months ahead could explain 70% of the record-low winter sea ice in 2023. .

These winds can cause ocean mixing in the Southern Ocean, pulling deeper, warmer water to the surface and suppressing sea ice growth. Winds can also push sea ice poleward toward the South Pole, preventing the sea ice edge from expanding northward, transporting heat from lower latitudes toward the poles, and generating waves that break up the sea ice. There is also.

Using the same approach for observations in 2024, researchers correctly predicted that this year would be another year of low sea ice extent in the Southern Ocean.

“Interestingly, despite how unusual winter sea ice conditions were in 2023 and 2024, our results show that they were surprisingly predictable more than six months in advance. ” said co-author Edward Blanchard Wrigglesworth. Science of Atmosphere and Climate.

Antarctic sea ice is important because it affects marine and coastal ecosystems and ocean-atmosphere interactions in the Southern Ocean. It also affects the Earth’s climate by reflecting sunlight in the southern hemisphere and influencing ice sheets and global flows.

“Antarctic sea ice significantly determines the rate of global warming and the stability of Antarctic ice,” Espinosa said. “In fact, sea ice serves to strengthen ice shelves, increasing their stability and slowing the rate of global sea level rise. This ice is also important for marine and coastal ecosystems.”

Summer has arrived in the Southern Hemisphere, but the current sea ice cover around Antarctica remains sparse and near an all-time low for this time of year.

“Our success in predicting these major sea ice loss events so far in advance demonstrates that we understand the mechanisms that cause them,” said co-author and Wisconsin Atmospheric and Climate Science Professor. Cecilia Bitts said. “Our models and methods are poised to predict future sea ice loss events.”