Two repeat crossings of Drake Passage in austral summer 2006: Short-term variations and evidence for considerable ventilation of intermediate and deep waters

• Published in: Deep Sea Research Part II: Topical Studies in Oceanography
• Main Authors: Provost, Christine, Renault, Alice, Barré, Nicolas, Sennéchael, Nathalie, Garçon, Véronique, Sudre, Joël, Huhn, Oliver
• Other Authors: Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), 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)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), 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)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2011
• Subjects: [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph]; [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph]; [SDE.MCG]Environmental Sciences/Global Changes; Antarctic; The Antarctic; Austral; Drake Passage; Shackleton; Barré; Shackleton Fracture Zone; Ona Basin; Yaghan Basin; Antarc*
• Online Access: https://hal.archives-ouvertes.fr/hal-00755385; https://doi.org/10.1016/J.DSR2.2011.06.009

International audience A high-resolution, full-depth, hydrographic section across Drake Passage with tracers and horizontal velocity measurements was repeated within three weeks in austral summer 2006. In-situ data (temperature, salinity, dissolved-oxygen and horizontal current velocities) are used to determine the location of the fronts and eddies of the Antarctic Circumpolar Current (ACC) inferred by Barré et al. (2011) from 7-day composite dynamic topography maps along the transect. Frontal displacements are about 40 km (2 stations) along the section. Considerable differences in properties between the two sections are observed throughout the whole water column with values as high as 0.2 °C in temperature, 0.01 in salinity, 0.03 kg m -3 in neutral density and 10 μmol kg -1 in dissolved-oxygen concentration found below a depth of 3000 m. Only part of the differences is attributable to frontal or eddy displacements along the section. The other part results from the spatial heterogeneity of water properties upstream the section and the funnelling of the flow due to the topographic constraints of the Shackleton Fracture Zone (SFZ). The considerable short-term differences in water properties in rather large-scale structures that cannot be accounted for by frontal motions along the section call for caution when interpreting differences in hydrographical properties obtained by oceanographic cruises that are years apart in terms of climatic signals.The two sections show efficient ventilation of Antarctic Intermediate Water (AAIW) by Winter Water (WW) in the Yaghan Basin, with an estimated eddy-enhanced subduction rate of over 170 m year -1 . The SFZ constitutes a barrier, causing the two Southern ACC Fronts (SACCF) branches to separate by about 400 km and creating sheltered conditions in partial isolation from the ACC, while promoting an active recirculation region in the Ona Basin. This active recirculation, marked by cyclonic eddies carrying cold, fresh and oxygenated water from south of the Southern Boundary of ...