Oceanic Regime Shift to a Warmer Continental Shelf Adjacent to the Shackleton Ice Shelf, East Antarctica

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: Ribeiro, Natalia, Herraiz-Borreguero, Laura, Rintoul, Stephen, R, Williams, Guy, Mcmahon, Clive, R, Hindell, Mark, Guinet, Christophe
• Other Authors: Institute for Marine and Antarctic Studies Hobart (IMAS), University of Tasmania Hobart, Australia (UTAS), CSIRO Wealth from Oceans Flagship, Commonwealth Scientific and Industrial Research Organisation Canberra (CSIRO), First Institute of Oceanography Qingdao (FIO), Ministry of Natural Resources of China, IMOS Animal Tagging New South Wales, Australia, Sydney Institute of Marine Science, Centre d'Études Biologiques de Chizé - UMR 7372 (CEBC), La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2023
• Subjects: [SDE]Environmental Sciences; Antarctic; East Antarctica; Shackleton; Shackleton Ice Shelf; Antarc*; Antarctica; Ice Shelf; Ice Shelves
• Online Access: https://hal.science/hal-04308599; https://hal.science/hal-04308599/document; https://hal.science/hal-04308599/file/RJGRO128_2023.pdf; https://doi.org/10.1029/2023JC019882

International audience Abstract The long‐held view that the East Antarctic margin is isolated from warm offshore waters has been challenged by recent observations showing incursions of warm modified Circumpolar Deep Water (mCDW) reaching several East Antarctic ice shelves. However, large areas of the East Antarctic continental shelf remain poorly observed, making it challenging to determine if the supply of oceanic heat to the ice shelves is changing. Here, we use temperature and salinity profiles to the west of the Shackleton Ice Shelf (SIS; ≈100°E) spanning 60 years to assess the variability of the water masses in the context of a changing climate. We document warming and freshening of shelf waters. Prior to 1996, cold mCDW water ( θ < −1.6°C) was found below the surface mixed layer and cold Dense Shelf Water (DSW) with a salinity of >34.5 dominated the water column. After 2010, warm mCDW (≥−1.0°C) was widespread over the continental shelf and DSW with salinity over 34.5 was no longer present. The mixing ratio of glacial meltwater indicates that warm mCDW observed in 2011 caused basal melting of the SIS, possibly reducing the salinity of DSW. Increased access of warm waters to the continental shelf may have also occurred on the eastern side of the ice shelf, where glaciological evidence shows the grounding line has retreated. These observations suggest a shift occurred prior to 2011 that has increased the ocean heat supply to the continental shelf and to the SIS, increasing basal melt and reducing DSW formation.