Antarctic atmospheric river climatology and impacts

• Main Author: Wille, Jonathan
• Other Authors: Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Université Grenoble Alpes 2020-., Vincent Favier, Francis Codron
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2021
• Subjects: Atmospheric rivers; Antarctica; Surface mass balance; Bilan de masse de surface; Antarctique; Rivières atmosphériques; [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; Antarctic; Antarctic Peninsula; Byrd; Dronning Maud Land; East Antarctica; Marie Byrd Land; Ross Ice Shelf; The Antarctic; West Antarctica; Antarc*; Antarctique*; Ice Shelf; Ice Shelves
• Online Access: https://theses.hal.science/tel-03276308; https://theses.hal.science/tel-03276308/document; https://theses.hal.science/tel-03276308/file/WILLE_2021_archivage.pdf

Due to the increased ability of the air to hold moisture with temperature, precipitation in Antarctica is expected to increase significantly over the next century. This process will undoubtedly lead to an increase in snow accumulation on the continent, thereby partially mitigating future sea level rise. However, recent observed trends in temperature and snow accumulation in Antarctica are insignificant and paradoxical. The role played by moisture intrusions in temperature and precipitation variability could partly explain this phenomenon. These events are known to transport warm air masses from the oceans to the Antarctic continent, but only individual and unrelated intrusion events have been described so far. In an earlier study of the Dronning Maud Land region, the description of atmospheric rivers (ARs) provided an innovative view to describe high intensity moisture intrusions. In this thesis, we develop an atmospheric river detection algorithm adapted to the polar regions, in order to create a climatology of these events at the Antarctic scale. Using the outputs of the regional climate model, MAR (Regional Atmospheric Model), we evaluate the impacts of atmospheric rivers on the melting in West Antarctic, ice-shelf stability on the Antarctic Peninsula ice shelves, and on snowfall across the Antarctic ice sheet.Atmospheric rivers are infrequent events with coastal areas of Antarctica experiencing AR conditions around only three days per year on average and this value is even lower in Antarctic interior. However, ARs control surface melting processes on West Antarctica and precipitation variability on East Antarctica. In the west, ARs entering the interior of the continent cause positive anomalies in downward longwave radiation via highly liquid-laden clouds and wind, resulting in a marked foehn effect along leeward slopes. Between 1979 and 2017, rivers were thus associated with about 40% of the summer melt on the Ross Ice Shelf (nearly 100% at higher altitudes on Marie Byrd Land) and 40-80% of the winter melt ...