Atmospheric rivers (ARs) are extreme hydrological events that have strong impacts on the Antarctic surface mass balance (SMB), through both snow accumulation and surface melt due to heating and rain. To estimate their impacts on future SMB, we study Antarctic ARs in an ensemble of 21st century simulations. While the number of detected ARs increases continuously when using a constant detection threshold based on historical moisture fluxes, it remains stable with an adaptive threshold evolving with the rising background moisture. However, ARs penetrate further into Antarctica following a wave number 3 pattern. In addition, the intensity of Antarctic ARs, measured by moisture fluxes, is simulated to increase following the Clausius-Clapeyron relation. The opposing SMB impacts become larger, with both increasing snowfall, and coastal surface melt and rainfall. Yet, their overall influence on the SMB is dominated by increased snow accumulation.

During atmospheric river (AR) landfalls on the Antarctic ice sheet, the high waviness of the circumpolar polar jet stream allows for sub-tropical air masses to be advected towards the Antarctic coastline. These rare but high-impact AR events are highly consequential for the Antarctic mass balance; yet little is known about the various atmospheric dynamical components determining their life cycle. By using an AR detection algorithm to retrieve AR landfalls at Dumont d’Urville and non-AR analogues based on 700 hPa geopotential height, we examined what makes AR landfalls unique and studied the complete life cycle of ARs to affect Dumont d’Urville. ARs form in the mid-latitudes/sub-tropics in areas of high surface evaporation, likely in response to tropical deep convection anomalies. These convection anomalies likely lead to Rossby wave trains that help amplify the upper-tropospheric flow pattern. As the AR approaches Antarctica, condensation of isentropically lifted moisture causes latent heat release that – in conjunction with poleward warm air advection – induces geopotential height rises and anticyclonic upper-level potential vorticity tendencies downstream. As evidenced by a blocking index, these tendencies lead to enhanced ridging/blocking that persist beyond the AR landfall time, sustaining warm air advection onto the ice sheet. Finally, we demonstrate a connection between tropopause polar vortices and mid-latitude cyclogenesis in an AR case study. Overall, the non-AR analogues reveal that the amplified jet pattern observed during AR landfalls is a result of enhanced poleward moisture transport and associated diabatic heating which is likely impossible to replicate without strong moisture transport.

Aerosols play a key role in polar climate, and are affected by long-range transport from the mid-latitudes, both in the Arctic and Antarctic. This work investigates poleward extreme transport events of aerosols, referred to as aerosol rivers (AeR), leveraging the concept of atmospheric rivers (AR) which signal extreme transport of moisture. Using reanalysis data, we build a detection catalog of polar AeRs for black carbon, dust, sea salt and organic carbon aerosols, for the period 1980–2022. First, we describe the detection algorithm, discuss its sensitivity, and evaluate its validity. Then, we present several extreme transport case studies, in the Arctic and in the Antarctic, illustrating the complementarity between ARs and AeRs. Despite similarities in transport pathways during co-occurring AR/AeR events, vertical profiles differ depending on the species, and large-scale transport patterns show that moisture and aerosols do not necessarily originate from the same areas. The complementarity between AR and AeR is also evidenced by their long-term characteristics in terms of spatial distribution, seasonality and trends. AeR detection, as a complement to AR, can have several important applications for better understanding polar climate and its connections to the mid-latitudes.