A new database of Antarctic extreme weather events over key ice shelves and weather system drivers

There is growing evidence of the climate of Antarctica being impacted by global heating. For example, the Antarctic sea ice extent has sharply declined since around 2015 and has been at record or near record lows in most years since. This has potential to result in accelerated break up of key ice shelves, which would contribute to global sea level rise and have further impacts on local and regional climate in and around Antarctica. There have recently been some notable extreme events such as the atmospheric river event in March 2022, and exceptional melt events over the Antarctic Peninsula in the summer of 2019/20. Here, we present a new database of Antarctic meteorological extremes over a selection of key ice shelves, using simulations from four regional climate models (RCMs: RACMO2, HCLIM, MetUM and MAR), driven by the ERA5 reanalysis, examining surface temperature, precipitation, wind and surface pressure. In addition, we examine trends in the frequency of extreme events above specified thresholds, and spatial anomaly patterns over Antarctica that are commonly associated with extreme events over key ice shelves. The RCM simulations have been compared with station observations close to the ice shelves, and we developed regressions to estimate simulated values during periods when not all of the RCMs were available. The results of the database are compared with weather system drivers such as atmospheric rivers, storm tracks and blocking, as well as teleconnections such as the Southern Annular Mode, to determine links between these drivers and the occurrence of meteorological extremes over the ice shelves. Over most of the ice shelves covered, the frequency of extreme events has not shown a strong trend over the period, but there is evidence of some extremes, especially high temperature extremes, having increased in frequency since the mid-2010s over some of the ice shelves, which could be related to the sharp decline in Antarctic sea ice extent.