Scientists from around the world have focused their attention on the Maud Rise region in the Southern Ocean, where an extraordinary polynya has formed in the Antarctic ice, comparable in size to Switzerland.
Polynyas are areas where sea ice breaks or melts, exposing the underlying ocean. Although this phenomenon is known, its current magnitude and persistence are cause for concern.
Factors explaining the opening of the polynya
The formation of this hole is attributed to a combination of factors:
- Ekman transport: wind-driven currents that drag salty water into the region
- Bottom warming: salt enhances ice melting
- Extratropical storms: displace ice and weaken its structure
- Atmospheric rivers: provide surface heat, favoring the opening
These elements have created the conditions for the polynya to remain open for weeks, something unusual in the recent history of the region.
Global impacts of a local phenomenon
Although they may seem isolated events, polynyas have global repercussions. They allow heat to escape from the ocean and carbon dioxide (CO₂) to be released into the atmosphere, which can accelerate climate change.
Furthermore, they modify the global ocean circulation, which regulates the distribution of heat and carbon throughout the planet.
“The footprint of polynyas can remain in the water for years,” explained Professor Sarah Gille from the University of California in San Diego.
Deep convection and brine: keys to climatic balance
The deep convection generated by these events transports carbon-rich water to the surface, where it can release CO₂, and sends oxygenated brine to the seafloor. This brine feeds the oceanic current chain that helps regulate global climate.
Their future frequency will depend on stronger winds and stormy skies, which are already changing with global warming.
Worrying trends in Antarctic sea ice
For the first time since observations began in the 1970s, a negative trend in Southern Ocean sea ice has been recorded, starting in 2016.
The same increase in warm and salty water that generated the 2017 polynya now appears to be thinning the ice in other areas of Antarctica.
An icy frontier influencing the entire planet
Scientists will continue monitoring the coming winters. Whether the polynya returns or not, its impact is already being felt in global oceanic and climatic dynamics.
The southernmost point of the planet remains a silent thermometer, whose signals must be heeded.
