Parallel Session 3: Elio Campitelli: ACCESS-S2 experiments suggest tropical oceans, not Antarctic sea ice, drove 2024 Southern Hemisphere stratospheric warming

ACCESS Workshop 2025 ACCESS Workshop Day 2
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ACCESS-S2 experiments suggest tropical oceans, not Antarctic sea ice, drove 2024 Southern Hemisphere stratospheric warming

Elio Campitelli


1. At seasonal and subseasonal timescales, it is thought that lower winter sea ice increases wave activity flux into the stratosphere, enhancing planetary wave 1 and 2 and weakening the polar stratospheric jet. Consistent with this view, in winter 2024 the Southern Ocean experienced low sea ice which coincided with high activity flux into the stratosphere and then a rare minor sudden stratospheric warming event.

  1. We investigate whether the low sea ice contributed to the event by running initial condition experiments with the ACCESS-S2 seasonal prediction system.

  2. The low-level atmospheric circulation though to have preconditioned the stratospheric warming event is not sensitive to Antarctic sea ice conditions but it disappears when changing tropical ocean initial conditions. This suggests that the tropical ocean and not Antarctic sea ice was the main driver of this circulation pattern.

  3. People interested in interactions between sea ice and the atmosphere.

  4. antarctic sea ice, sea ice-atmosphere interactions, atmospheric circulation, stratospheric warming


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