A huge vortex of ocean water surrounding Antarctica, a swirling volume 100 times larger than all the world’s rivers combined, is speeding up due to climate change.
At least, that’s the conclusion of a new study that examined the behavior of this polar ocean vortex over the past 5.3 million years, using sediment core samples from Earth’s roughest and most remote waters.
As one co-author of the new study, a geochemist at Columbia University, put it, “This is the mightiest and fastest current on Earth.”
‘It is perhaps the most important current of the Earth’s climate system.’
Sea ice plays an important role in maintaining Earth’s energy balance while helping keep the polar regions cool thanks to its ability to reflect more sunlight back to space. Pictured above, some of that same sea ice, in the water off Cuverville Island in Antarctica
That geochemist, Dr. Gisela Winckler of the Lamont-Doherty Earth Observatory in Columbia, said the new study “implies that the retreat or collapse of Antarctic ice is mechanistically linked to enhanced ACC flow.”
It is “a scenario,” she said, “that we are seeing today regarding global warming.”
Powered by persistent westerly winds, the ACC rotates clockwise around the southernmost icy continent at a speed of about 4 miles per hour, whisking about 6 billion cubic feet of water per second.
Geologists currently believe that the conditions for creating the vortex first arose after Antarctica separated from Australia 34 million years ago, during Eocene tectonic shifts.
But the vortex, scientists say, only entered its modern forest 12 to 14 million years ago.
Above is a map of simulated ocean velocities 100 meters below the surface, with the blue-gray areas showing weaker currents and the white areas showing the stronger currents of the Antarctic Circumpolar Current (ACC) vortex. The ACC behavior here is derived from the satellite ‘altimetry16’. The white stars above indicate the research team’s sediment core drilling locations
In 2021, French explorer and environmentalist Jean-Louis Etienne announced a Polar Pod that will complete two circuits around Antarctica every three years, carried by the Antarctic Circumpolar Current, for similar polar research.
About 40 scientists from a dozen countries contributed to a new study, published Wednesday in Naturesome aboard the drillship JOIDES Resolution, which was deployed to collect sediment samples from the ocean floor.
The research vessel conducted a two-month voyage in the darkness of the Antarctic winter (May to July 2019) near Point Nemo, more than 1,600 miles from the nearest piece of surface land, the Pitcairn Islands.
Waves more than 60 feet high threatened the JOIDES as the crew drilled and dredged 500 to 700 feet of sediment cores for their research into the vortex’s many millennia of activity.
Advanced X-ray techniques helped the researchers analyze the changing particle sizes of ancient deep-sea sediment.
Smaller particles, they reason, settle more during times of slower currents, while only larger particles will have the weight to fall to the ocean floor during faster ACC currents.
After years of research, the core samples revealed multiple epochs of changing ACC rate that corresponded with known shifts in Earth’s climate.
The project was then able to match this new data with previous studies of the West Antarctic Ice Sheet, providing compelling evidence that the ACC’s fast flow periods corresponded to known times when Antarctica’s glacial ice shrank.
“This ice loss can be attributed to increased heat transport southward,” says Dr. Frank Lamy, lead author of the study.
“A stronger ACC,” warned Dr. Lamy, who teaches at Germany’s Alfred Wegener Institute, “means more warm, deep water reaching the edge of the Antarctic ice shelf.”