Climate change: Atmospheric extremes add to Antarctic ice shelf vulnerabilities

Sixty percent of iceberg calving events — that form new icebergs — around the Antarctic Peninsula Larsen ice shelves between 2000 and 2020, were triggered by extreme atmospheric conditions. The findings, published in Communications Earth & Environment, suggest that under future warming projections, the same processes may put the Larsen C ice shelf at-risk of collapse.

Ice shelf collapse events in Antarctica are thought to accelerate continental ice loss, which contributes to rising sea-levels. Atmospheric rivers are narrow bands of high moisture, that move through the atmosphere like a river. These streams originate in the subtropics or mid-latitudes, and can cause heatwaves, sea ice melting and ocean swell waves, which can lead to iceberg calving and ice shelf collapse. In recent decades, the Larsen A and Larsen B ice shelves on the Antarctic Peninsula have both collapsed dramatically, in 1995 and 2002, respectively. These events have been linked to ice surface melting and stress associated with ocean waves from storms.

To determine the impact of atmospheric rivers on ice shelves in Antarctica, Jonathan Wille and colleagues identified 21 ice shelf calving and collapse events on the Larsen ice shelves between 2000 and 2020. Using a detection algorithm for atmospheric rivers, the authors found that 13 of the 21 calving and collapse events were preceded by a landfall of strong atmospheric rivers within 5 days of the event.

The authors argue that future ice-sheet stability models need to include short-term extremes in atmospheric behaviour, and not rely solely on average conditions.