The contribution of the surface temperature inversion to Antarctic warming

Abstract. Antarctica is expected to warm faster than the global average throughout the 21^st century in a phenomenon called Antarctic amplification. The polar atmosphere is unique in having a strong and persistent surface temperature inversion layer, and its changing properties can dramatically affect polar warming. In this work, we reveal mechanisms behind Antarctic amplification by quantifying the contribution of this surface temperature inversion to the region’s near-surface warming. Global climate models often miss the vertical resolution and physical processes needed to correctly simulate the intense near-surface inversion. Here, we downscale four global climate models with the regional climate model MAR (Modèle Atmosphérique Régional) to decompose the Antarctic near-surface potential temperature into the background potential temperature and the surface temperature inversion strength. From the late 20^th to the late 21^st century, we attribute 72 % of July near-surface warming over the Antarctic continent and sea ice to large-scale background warming under the Shared Socioeconomic Pathway SSP5-8.5. However, the spatial variability in this warming is driven by surface processes through their weakening of the surface temperature inversion, which explains the remaining 28 % of warming. Over the ocean, this weakening is well predicted by sea ice loss, and accounts for 41 % of the near-surface warming. By contrast, the weakening of the inversion explains 16 % of near-surface warming on the continent, where it is correlated with stronger present-day atmospheric stability, which suggests that the lapse-rate feedback contributes significantly to spatial variability in warming. The particularly strong contribution of sea ice loss to the weakening of the inversion could explain the asymmetry between Arctic and Antarctic amplification. Variability in the inversion strength could also account for discrepancies between paleoclimate proxy records.