Over a large part of Antarctica, the surface mass balance (SMB) is controlled by a few extreme events, resulting in a high natural variability of this parameter. In particular, extreme moisture intrusions linked to Southern Ocean Atmospheric Rivers (ARs) have been recently demonstrated to be major sources of both snow accumulation, heating and surface melt. Despite their key role, there is a general omission of AR variability, and more broadly of extreme events, in studies of past and future Antarctic climate and SMB. ARCA will assess the impact of ARs on the surface mass balance of Antarctica and will explore to what extent past AR activity can be recorded in ice cores. To reach this goal, ARCA is organized in 4 working packages. 1) ARCA will use recent novel numerical methodologies for identifying ARs applied to global and regional circulation models (GCMs and RCMs respectively). New algorithms will be applied to historical, present and future climate simulations. 2) ARCA will provide new field measurements of water stable isotopes and chemistry composition of snow precipitation and air masses from Adelie and Wilkes Lands, and 3) apply a regional scale modeling of water stable isotopes to interpret the signal observed in the field. 4) ARCA will finally revisit data from existing ice cores (aerosol content, e.g. sea salt, insoluble particles, water isotopes). Following this methodology, ARCA proposes to: 1) understand how natural variability and external forcings control the AR activity. 2) quantify AR moisture and heat transport towards Antarctica and their impacts on the SMB of Antarctica. 3) describe AR impact on the isotopic and aerosol contents of air masses transported through East Antarctica, 4) analyze the processes (e.g., moisture origin, sublimation of hydrometeors) producing characteristic signals in air masses during ARs, 5) estimate the induced bias in ice core records in regards to past temperature reconstructions. 6) Evaluate (qualitatively) past AR variability and the resulting bias in current estimates of past millenium climate in Antarctica. The ARCA project will deliver products that describe AR climatology and variability (occurrence maps, statistics), their atmospheric moisture signature (time-series of isotopes and aerosol content), and their impacts on Antarctic climate and SMB (through maps of induced melting and accumulation). Results will be presented for the 20th and 21st centuries, aiming in particular at projecting observationally constrained impacts of ARs on the SMB. ARCA will define a multi proxy approach to define how past AR could be retrieved in ice cores and provide a metric using water isotopic composition in ice cores to qualitatively define periods of higher and lower AR activity over the past millennium. Finally, ARCA will define the regions of Adelie and Wilkes Lands where ice cores should be drilled to best capture the AR and their influence in past climate variability. The ARCA consortium presents recognized experts from the IGE, LSCE and LOCEAN in particular in atmospheric modeling with polar-Regional Circulation Models and General Circulation Models, AR detection and estimation surface mass balance for Antarctica. The project will also rely on the broad expertise of the group in the interpretation of water isotopes and aerosol contents in air samples and ice cores.