Antarctica records second heatwave in 2 years: What's causing it?
Antarctica, the world's coldest continent, is currently witnessing a deep-winter heatwave for the second time in two years. Ground temperatures have been averaging 10°C above normal since mid-July, with peaks reaching 28°C higher on certain days. In East Antarctica, which constitutes two-thirds of the continent, temperatures are fluctuating between -25°C and -30°C. This is a significant increase from the usual deep-winter temperatures of -50°C to -60°C.
Weakening polar vortex: The primary cause
The unusual warming is primarily attributed to the weakening of the polar vortex, a band of cold air and low-pressure systems that encircles the Earth's poles in the stratosphere. Thomas Bracegirdle, Deputy Science Leader of the British Antarctic Survey's Atmosphere, Ice and Climate team said "the vortex usually remains strong and stable during winter in the southern hemisphere — keeping cold air trapped...and not letting hot air come in." "But it has been disturbed this year by large-scale atmospheric waves."
How does a weakened polar vortex impact temperatures
The disturbance of the polar vortex has resulted in the release of trapped cold air and the influx of warmer air into the region. As this warmer air descends from the upper atmosphere, it raises ground temperatures. Bracegirdle highlighted that a weakened southern hemisphere vortex is a rare occurrence, expected to happen only once every two decades on average.
Other contributing factors to Antarctica's heatwave
Apart from the weakening polar vortex, other elements may also be contributing to the heatwave in Antarctica. In June, the extent of Antarctic sea ice was recorded as the second-lowest ever for that time of year. Sea ice plays a vital role in maintaining low temperatures in polar regions by reflecting sunlight back into space and acting as a barrier between cold air and warmer water below.
Antarctica is warming at nearly twice the global rate
According to a 2023 study, global warming is impacting Antarctica at nearly twice the rate of the rest of the world. The Intergovernmental Panel on Climate Change estimates that while Earth is warming at a rate of 0.14-0.18°C per decade, Antarctica is warming at a rate of 0.22-0.32°C per decade. The Antarctic Ice Sheet, which covers 98% of the continent and holds over 60% of the world's total freshwater, could submerge coastal cities and reshape global geography if entirely melted.
Rising temperatures could disrupt global ocean circulation system
Rising temperatures also threaten to disrupt the global ocean circulation system, which regulates climate by storing and transporting heat, carbon, nutrients, and freshwater worldwide. A 2023 study in Nature showed that melting Antarctic ice is slowing this circulation system by reducing surface water salinity and density, thereby diminishing its downward flow to the ocean's bottom. This slowdown could result in oceans absorbing less heat and CO2, exacerbating global warming and increasing the frequency and intensity of extreme weather events.
