Current and projected patterns of warming and marine heatwaves in the Southern Indian Ocean

• Published in: Progress in Oceanography
• Main Authors: Azarian, Clara, Bopp, Laurent, Pietri, Alice, Sallée, Jean-Baptiste, d'Ovidio, Francesco
• Other Authors: Processus et interactions de fine échelle océanique (PROTEO), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL), Instituto del Mar del Peru (IMARPE), LEFE led by CNRS-INSU, France (projects KERTREND and KERTREND-SAT), European Project: 820989,H2020-EU.3.5.1.,COMFORT(2019)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2023
• Subjects: Global climate models; Ocean warming; Ocean extremes; Southern Indian Ocean; [SDU]Sciences of the Universe [physics]; Antarc*; Antarctic
• Online Access: https://insu.hal.science/insu-04139547; https://insu.hal.science/insu-04139547/document; https://insu.hal.science/insu-04139547/file/draft_Current_and_projected_patterns.pdf; https://doi.org/10.1016/j.pocean.2023.103036

International audience The Southern Indian Ocean (20-120°E, 70-30°S) hosts an exceptional biodiversity that contributed to the inscription of the French and Australian natural reserves on the UNESCO World Heritage List. This region is a "hot spot" for ocean heat uptake and already experiences intense marine heat waves (MHW), as evidenced in 2011/2012 over the Kerguelen Plateau. In the coming decades, this region is also expected to face supplemental anthropogenic warming, depending on future greenhouse gas emissions, with unknown consequences for its marine ecosystems. Here, we present a regional analysis of ocean warming and MHW based on the analyses of historical observations and Coupled Model Intercomparison Project Phase 6 (CMIP6) climate projections. Consistent with observations over the last decades, we find an intensification through the 21st century of surface warming and MHW over a band located between 40°S and 55°S within the Antarctic Circumpolar Current region. CMIP6 models also project much faster climate velocities (i.e. the speed and direction at which isotherms drift in the wake of climate change) in the mesopelagic (200-1000 m) than at the surface (0-200 m). Lastly, a comparison between the two Shared Socioeconomic Pathways (SSP1-2.6 and SSP2-4.5) analysed in this study shows much larger changes in the second half of the 21st century for the higher emission scenario. These results suggest that the subantarctic islands will probably be mostly affected by warming and MHW under both scenarios, although committing to SSP1-2.6 could substantially alleviate the pressure on ecosystems in the long term. This study also highlights the need to consider a tri-dimensional environment that may evolve at different paces when designing efficient conservation measures.