Despite their relative recentness in the minds of polar scientists, atmospheric rivers have quickly become crucial element of Antarctic meteorological and climatological discussions. The idea behind this workshop is to gather this budding interest and see where our research currently stands. Since just 2014, atmospheric rivers have been identified as a sub-tropical link to the Antarctic continent and create extreme atmospheric conditions that are largely consequential to surface melt, snowfall, and ice-shelf stability. Still, as more researchers from various backgrounds have entered the atmospheric river fray, the scientific questions have grown to include representation of atmospheric rivers in model simulations, retrieving the atmospheric river signal isotopic signature from ice cores and direct measurements, and understanding their meteorological origins.

The goal from this workshop is to aggregate the current state of knowledge, promote the discussion around Antarctic atmospheric rivers, and explore future collaborations for projects. And then find time for a nice walk in the French Alpes afterwards. 

This will be a hybrid workshop with physical attendance on the Institut des Géosciences de l'Environnement (IGE) on the Université Grenoble Alpes campus. Details for remote attendance will be provided at a later date. If you have any questions on registration or anything else, feel free to email Jonathan Wille at jonathan.wille@univ-grenoble-alpes.fr

Abstract submission deadline: May 23

Atmospheric river chemistry and paleoclimatology

An understanding of long-term AR frequency and intensity is essential to define the natural variability of ARs in Antarctica. However, there is currently no record of Antarctic AR activity beyond the satellite. It would be helpful to retrieve ARs from ice cores, but this remains difficult and elusive. For AR retrieval in this manner, the air masses associated with ARs must have large anomalies in their chemical signatures and represent a large contribution to annual accumulation totals. In other words, ARs must be associated with both 1) large amounts of precipitation and 2) large isotopic or chemical anomalies and 3) finally, the signal must be preserved in firn and ice. Several studies have found that the atmospheric water vapor during an AR event can have a largely anomalous isotopic composition. ARs are also associated with long-range transport of dust and biological particles. However, the potential link of intercontinental transport of moisture and natural aerosols on Antarctic air composition is not well studied. The post-depositional processes and long-term preservation of the signal in the archive are still unknown. This session aims to clarify the state of knowledge the AR signal in isotopic and chemical measurements and snow/ice accumulation records with the objective of analyzing the potential value of firn and ice cores to study past AR activity.

Atmospheric river dynamics

Atmospheric rivers occurrences are highly variable but are concentrated during atmospheric circulation patterns that favor strong meridional moisture transport. Strong atmospheric ridges/blocks are required for AR landfalls in Antarctica. Blocking over the downstream part of the circulation acts to channel meridional advection of heat and moisture from lower latitudes to Antarctica. Deep convection and anomalously warm SSTs appear to initiate Rossby wave propagation towards Antarctica and set up moisture transport corridor. However, little is known on the dynamical processes controlling the generation, life, and demise of ARs, and what type of large-scale climate situation is more likely to develop ARs. This session aims to discuss the state-of-the-art modeling results and observations that shed more light on the dynamics around atmospheric rivers.

Atmospheric river impacts in the Antarctic

The ARs carry large amounts of heat and moisture from the Southern Ocean, which not only impact the Antarctic coast, but can also penetrate deep into the continent. We observe that ARs cause surface melting from increased downward longwave radiation and foehn wind enhancement. Meanwhile, sea-ice displacement and ocean swell generation act as additional stresses on the Antarctic Peninsula ice shelves that lead to their destabilization. However, strong ARs are known to control the most intense precipitation events and the interannual variability of accumulation over large areas of Antarctica. A single AR could simultaneously contribute positively and negatively to the Antarctic SMB by causing both heavy snowfall and melting in different affected regions. In addition, there are possible biological impacts over the Southern Ocean and Antarctic coastal regions that have yet to be explored. This session aims to describe all potential impacts of ARs the Antarctic and how these impacts might vary in the future.

Atmospheric river detection and simulation

Like most regions of the world, AR analysis over the Antarctic is heavily influenced by the method of AR detection. As recently highlighted by a recent study from Atmospheric River Tracking Method Intercomparison Project (ARTMIP), regional and global AR detection algorithms can detect rivers at very different rates.  These differences in AR detection methods make the study of future AR changes over Antarctic even more difficult. Changes in AR behavior will depend on future changes in the large-scale climate variability that controls AR frequency and how AR intensity will react to increased moisture with global warming. Most future AR projections are based on AR detection that relies on thresholds based on moisture transport values in the historical period. This session aims to disucss the uncertainty in various AR detection methods applied to various model products, and evaluating the associated uncertainty in assessing past, present, and future AR activity. Idealized simulations and experiments of Antarctic AR activity are also welcome.