Antarctic ozone loss linked to unexpected Southern Ocean cooling from 1982 to 2005

The Southern Ocean has exhibited a puzzling trend of cooling during the late 20th and early 21st centuries, despite rising greenhouse gas levels. A new study published on July 3, 2026, in Geophysical Research Letters by researchers from Princeton University suggests that human-driven depletion of ozone over Antarctica significantly contributed to this cooling from 1982 to 2005.

Understanding the Role of Ozone Depletion

The formation of the ozone hole is primarily attributed to human-made chemicals released throughout the 20th century. This depletion cools the lower stratosphere, altering the temperature difference between polar regions and the tropics. These changes strengthen the westerly winds encircling Antarctica, pushing them closer to the continent.

According to lead researcher Shouwei Li, the loss of ozone intensifies these winds, which in turn influences ocean temperatures and sea ice formations around Antarctica. The study highlights that the cooling effect observed in the Southern Ocean is a result of complex atmospheric and oceanic interactions.

Impact of Wind Patterns on Ocean Cooling

As the westerly winds strengthen and shift poleward, they alter how ocean waters circulate. This phenomenon, known as Ekman transport, typically drives surface waters northward. The research indicates that enhanced winds, driven by ozone loss, increase this northward movement of surface waters south of 46°S latitude, effectively transporting cold water away from Antarctica.

This process cools much of the Southern Ocean surface, while other factors, such as surface heat exchange with the atmosphere, provide insufficient warming to counteract the dominant cooling effect from the winds.

Long-Term Effects on Sea Ice and Climate Models

The study reveals that ozone-driven cooling has also influenced regional sea ice expansion, particularly in the Ross Sea. This observation aligns with satellite-era data showing increases in sea ice in certain Southern Ocean areas, despite overall global declines.

However, the effects are not uniform; some regions continue to experience declines in sea ice. The researchers found that while ozone depletion contributes to these patterns, it alone cannot explain the complete changes observed. This nuanced understanding helps clarify why climate models may predict warming in the Southern Ocean, even as actual observations reveal periods of cooling.