What’s El Niño got to do with it?
In our new research, we untangle how Antarctic snow accumulation varies due to the influence of El Niño events. El Niño describes the warming of ocean surface temperatures in the central and eastern tropical Pacific Ocean, leading to a shift in weather patterns and circulation across the Pacific and in Australia and Antarctica.
El Niño events can be classified as different types or ‘flavours’, defined by the location of the warmest sea surface temperatures in the tropical Pacific, either in the central equatorial Pacific –called “Central Pacific El Niño” – or the eastern equatorial Pacific — called “Eastern Pacific El Niño”.
Schematic of Central Pacific and Eastern Pacific El Niño idealised sea surface temperature and atmospheric conditions. Figure from Fruend et al (2019) The Conversation
El Niño causes changes in Antarctic temperature and precipitation, driven by changes in atmospheric circulation, which bring warm, moisture-laden air over the continent. El Niño conditions also enhance the ocean-driven melting of glaciers, such as Thwaites Glacier, as more relatively warm water reaches underneath the ice shelf and melts the glacier. Recent research has established that a prolonged extreme El Niño event is likely to have caused the onset of Thwaites glacier retreat, which currently contributes 4% of global sea level rise.
How Central Pacific El Niño and Eastern Pacific El Niño events impact the Antarctic Ice Sheet differently is a crucial question because El Niño type, frequency and intensity are all projected to change in a warming climate. Importantly, no previous studies have considered how different El Niño types influence Antarctic snow accumulation.
Our research shows West Antarctic snow accumulation increases are more widespread during Central Pacific El Niño events than during Eastern Pacific El Niño events. We show that Central Pacific El Niño events impact West Antarctica earlier in the yearly cycle than Eastern Pacific El Niño, and these accumulation impacts last longer throughout both austral winter and spring.
Map of Antarctic surface mass gain (accumulation increases) in green, surface mass loss (accumulation decreases) in pink during Central Pacific El Niño (top row) and Eastern Pacific El Niño (bottom row), during austral winter (left column) and spring (right column). Stipples show 5% significance.