An extreme high temperature event in coastal East Antarctica associated with an atmospheric river and record summer downslope winds

High surface temperatures are important in Antarctica because of their role in ice melt and sea level rise. We investigate a high temperature event in December 1989 that gave record temperatures in coastal East Antarctica between 60º and 100º E. The high temperatures were associated with a pool of warm lower tropospheric air with December temperature anomalies of >14º C that developed in two stages over the Amery Ice Shelf. Firstly, there was near-record poleward warm advection within an atmospheric river. Secondly, synoptically-driven downslope flow from the interior reached unprecedented December strength over a large area, leading to strong descent and further warming in the coastal region. The coastal easterly winds were unusually deep and strong, and the warm pool was advected westwards, giving a short period of high temperatures at coastal locations, including a surface temperature of 9.3ºC at Mawson, the second highest in its 66-year record.