Climate: Stronger El Niño would warm Antarctic shelf ocean

Projected increases in the amplitude of recurring climate pattern El Niño may lead to warming of Antarctic shelf ocean water, which may accelerate melting of stationary ice shelves and sheets but slow floating sea ice reduction. The findings are published in Nature Climate Change.

The El Niño Southern Oscillation (ENSO) centred in the tropical Pacific is a key driver of climate variability around the world, as both its warm phase, El Niño, and its colder phase, La Niña, influence weather conditions, even in remote regions. Climate change is expected to increase the magnitude of this climate pattern, making both El Niño and La Niña events stronger. This increase in ENSO variability may slow down the warming of the mid-latitude Southern Ocean, but it is unclear how the variability would affect warming closer to Antarctica.

Wenju Cai and colleagues focused on the effects that increased ENSO variability would have on warming near the Antarctic shelf ocean, finding in climate models that an increase in ENSO variability leads to reduced warming near surface but accelerated warming of deeper waters.  Models with increased ENSO variability show a reduced upwelling of deeper, warmer waters, leading to the slower warming of surface water. These models show reduced melting of floating sea ice, but the accelerated warming of deeper waters can interact with ice shelves and sheets and could result in more melting of these ice masses.

As these models do not contain a detailed ice sheet model, the magnitude of this effect on overall ice loss is not yet clear.