Recent climate variability around the Kerguelen Islands (Southern Ocean) seen through weather regimes

• Published in: Journal of Applied Meteorology and Climatology
• Main Authors: Pohl, Benjamin, Saucède, Thomas, Pergaud, Julien, Féral, Jean-Pierre, Richard, Yves, Favier, Vincent, Verfaillie, Deborah, Krasniqi, Ylber
• Other Authors: Biogéosciences UMR 6282 (BGS), Université de Bourgogne (UB)-Centre National de la Recherche Scientifique (CNRS), Institut méditerranéen de biodiversité et d'écologie marine et continentale (IMBE), Avignon Université (AU)-Aix Marseille Université (AMU)-Institut de recherche pour le développement IRD : UMR237-Centre National de la Recherche Scientifique (CNRS), Université Grenoble Alpes (UGA), 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 )
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2021
• Subjects: Southern Ocean; Antarctic Oscillation; Climate variability; Interannual variability; Southern Oscillation; [SDU]Sciences of the Universe [physics]; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; Antarc*; Antarctic; Antarctica; Kerguelen Islands
• Online Access: https://hal.science/hal-03235508; https://hal.science/hal-03235508/document; https://hal.science/hal-03235508/file/2021_Pohl_Journal%20of%20Applied%20Meteorology%20and%20Climatology_Recent%20climate%20variability%20around%20the%20Kerguelen%20Islands%20%28Southern%20Ocean%29%20seen%20through%20weather%20regimes.pdf; https://doi.org/10.1175/JAMC-D-20-0255.1

International audience Abstract Daily weather regimes are defined around the Kerguelen Islands (Southern Ocean) based on daily 500 hPa geopotential height anomalies derived from the ERA5 ensemble reanalysis over the period 1979-2018. Ten regimes are retained as significant. Their occurrences are highly consistent across reanalysis ensemble members. Regimes show weak seasonality and non-significant long-term trends in their occurrences. Their sequences are usually short (1-3 days), with extreme persistence values above 10 days. Seasonal regime frequency is mostly driven by the phase of the Southern Annular Mode over Antarctica, mid-latitude dynamics over the Southern Ocean like the Pacific South American mode, and to a lesser extent, tropical variability, with significant but weaker relationships with El Niño Southern Oscillation. At the local scale over the Kerguelen Islands, regimes have a strong influence on measured atmospheric and oceanic variables, including minimum and maximum air temperature, mostly driven by horizontal advections, sea water temperature recorded 5 m below the surface, wind speed and sea level pressure. Relationships are weaker for precipitation amounts. Regimes also modify regional contrasts between observational sites in Kerguelen, highlighting strong exposure contrasts. The regimes allow improving our understanding of weather and climate variability and interactions in this region; they will be used in future work to assess past and projected long-term circulation changes in the southern mid-latitudes.