Coherent Seasonal Acceleration of the Weddell Sea Boundary Current System Driven by Upstream Winds

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: Le Paih, Nicolas, Hattermann, Tore, Boebel, Olaf, Kanzow, Torsten, Lüpkes, Christof, Rohardt, Gerd, Strass, Volker, Herbette, Steven
• Other Authors: Laboratoire d'Océanographie Physique et Spatiale (LOPS), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2020
• Subjects: Southern Ocean; Weddell Sea; Antarctic slope current; surface stress; flow strength; teleconnection; [SDU]Sciences of the Universe [physics]; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; Antarctic; Antarctic Peninsula; Austral; The Antarctic; Weddell; Antarc*; Ice Sheet; Ice Shelves; Sea ice
• Online Access: https://insu.hal.science/insu-03683220; https://insu.hal.science/insu-03683220/document; https://insu.hal.science/insu-03683220/file/JGR%20Oceans%20-%202020%20-%20Le%20Paih%20-%20Coherent%20Seasonal%20Acceleration%20of%20the%20Weddell%20Sea%20Boundary%20Current%20System%20Driven%20by%20Upstream.pdf; https://doi.org/10.1029/2020JC016316

International audience The Weddell Sea is of global importance in the formation of dense bottom waters associated with sea ice formation and ocean-ice sheet interaction occurring on the shelf areas. In this context, the Weddell Sea boundary current system (BCS) presents a major conduit for transporting relatively warm water to the Weddell Sea ice shelves and for exporting some modified form of Wedell Sea deep and bottom waters into the open ocean. This study investigates the downstream evolution of the structure and the seasonality of the BCS along the Weddell Sea continental slope, combining ocean data collected for the past two decades at three study locations. The interannual-mean geostrophic flow, which follows planetary potential vorticity contours, shifts from being surface intensified to bottom intensified along stream. The shift occurs due to the densification of water masses and the decreasing surface stress that occurs westward, toward the Antarctic Peninsula. A coherent along-slope seasonal acceleration of the barotropic flow exists, with maximum speed in austral autumn and minimum speed in austral summer. The barotropic flow significantly contributes to the seasonal variability in bottom velocity along the tip of the Antarctic Peninsula. Our analysis suggests that the winds on the eastern/northeastern side of the gyre determines the seasonal acceleration of the barotropic flow. In turn, they might control the export of Weddell Sea Bottom Water on seasonal time scales. The processes controlling the baroclinic seasonality of the flow need further investigation.