Antarctica’s Polar Vortex to Split, Global Impacts Expected

The Antarctic polar vortex is on the brink of a rare split, the first occurrence in over two decades, triggered by a sudden surge in stratospheric temperatures.

Should the vortex divide, it could lead to significant warming in Antarctica while potentially causing an exceptionally hot summer in Australia and South America.

Typically, the southern polar vortex, a circular wind pattern, moves clockwise and confines cold air over Antarctica during the southern hemisphere winter, maintaining internal temperatures around -80°C (-112°F).

However, this year has shown signs of instability within the vortex. In mid-July, there was a noticeable deceleration in the vortex’s wind speeds from 300 to 230 kilometers per hour, allowing colder air to descend and causing a record rise in stratospheric temperatures. This resulted in internal temperatures rising nearly 20°C (36°F) above the usual -80°C average.

Steven Keates from the UK Met Office observed a further slowdown in early August followed by another sharp temperature increase in the upper stratosphere. This displacement of the vortex from its usual position at the South Pole caused cold polar air to flow towards Australia, New Zealand, and South America, while warmer air shifted towards Antarctica, potentially leading to a heatwave.

A slower wind speed could reverse the vortex’s direction to anticlockwise, a phenomenon known as sudden stratospheric warming.

“Repeated reductions in wind speeds might heighten the likelihood of the vortex splitting and a sudden stratospheric warming event occurring this year,” Keates explained.

Simon Lee from the University of St Andrews noted that even minor disruptions to the vortex can have significant cumulative effects. “Minor warmings can set the stage for more severe events later. Given the typically small variability in the Antarctic vortex, even slight anomalies can rapidly escalate into extreme events,” he stated.