Why Did the Heatwave in Antarctica Surprise Scientists?

Climate scientists are concerned about the increasing frequency of unexpected events, such as the March 2022 heatwave in Antarctica. The extreme heatwave, which reached temperatures up to 40°C (72°F) above normal, was the most intense recorded anywhere in the world. A global research project led by Swiss climatologist Jonathan Wille and experts from 14 countries aimed to understand the reasons behind the event and its damage. The team published two groundbreaking papers, providing scientists with a deeper understanding of the links between the tropics and Antarctica and allowing the global community to prepare for a warmer world.

The papers describe a complex event that began half a world away from Antarctica, combining La Niña conditions, tropical heat near Indonesia, and southern African weather troughs into a late Indian Ocean tropical cyclone season.

Between late February and late March 2022, 12 tropical storms had brewed, with five storms turning into tropical cyclones. Heat and moisture from these cyclones merged, leading to a meandering jet stream transporting the air across the planet to Antarctica. This jet stream also blocked the eastward passage of a high pressure system, causing the most intense atmospheric river ever observed over East Antarctica.

The Conger Ice Shelf collapsed due to a heatwave in March, which caused most inland temperatures to stay below zero. The heatwave affected 3.3 million square kilometers in East Antarctica, an area about the size of India. The impacts included widespread rain and surface melt along coastal areas, but inland, tropical moisture fell as snow, which offset ice loss in Antarctica for the year. This temporary reprieve from Antarctica’s contribution to global sea-level rise.

The study was made possible through international collaboration across Antarctica’s scientific community, demonstrating the importance of peaceful international cooperation, as a cornerstone of the Antarctic Treaty.

The extraordinary heatwave also showed how compounding weather events in the tropics can affect the vast Antarctic ice sheet. The heatwave further reduced the extent of sea ice, which was already at record lows, resulting in the lowest summer and winter sea ice ever recorded. This highlights how disturbances in one year can compound in later years.

Tropical heat can cause the collapse of unstable ice shelves, which contribute to global sea-level rise. These temperature anomalies occur in Antarctica about once a century but are more frequent under climate change. The research helps the global community plan for various scenarios, such as predicting ice melt during a heatwave, estimating sea level rise in the West Antarctic Doomsday glacier, and preparing coastal communities for sea level rise beyond current calculations. The findings can help governments prepare coastal communities for potential sea-level rise.

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