How do extreme ENSO events affect Antarctic surface mass balance?

Abstract. Extreme El Niño-Southern Oscillation (ENSO) events have far-reaching impacts globally, yet their impacts on Antarctica are poorly understood. In particular, how extreme ENSO events influence Antarctica's mass balance remains uncertain, with few studies considering how extreme events could differ from moderate events. Here, we examine the impacts of past extreme El Niño and strong La Niña events over the period 1979–2018 on surface mass balance of Antarctica using a reanalysis-forced regional climate model. We find that Antarctic surface mass balance does not vary significantly during most of the simulated extreme events. Regional impacts differ between individual events and cannot be generalized across all extreme events. Enderby Land is an exception: significant increases in surface mass balance – approximately 32 % of the regional annual average – occur during all extreme El Niño events. Furthermore, during the 2015/16 extreme El Niño event, widespread and significant surface mass balance changes occurred across East and West Antarctic catchments. These changes are remarkable, extending outside the respective catchments' 5th and 95th probability distributions for September-November period. Our results suggest that future extreme ENSO events may continue to cause significant impacts in Antarctic surface mass balance. However, the magnitude and polarity of the potential impacts cannot be inferred from the limited information available on extremes contained in four decades of historical data. Further investigations using ice core data and large ensemble model simulations are needed to better understand the drivers of the spatial and temporal variability in this system.