The deep waters from the Southern Ocean at the entry to the Argentine Basin |
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| Institution: | 1. Department of Mechanical Engineering, University of Bath, Bath BA2 7AY, UK;2. Heron Island Research Station, The University of Queensland, Queensland 4680, Australia;3. Imaging and Analysis Centre, Natural History Museum, Cromwell Road, London SW7 5BD, UK;4. Department of Life Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK;5. Department of Chemistry, University of Bath, Bath BA2 7AY, UK;1. Department of Earth Science, University of Bergen, Allégaten 41, N-5007 Bergen, Norway.;2. Department of Geosciences, University of Oslo, P.O. Box 1047, Blindern, N-0316 Oslo, Norway;3. Geology Section, Department of Geosciences and Natural Resource Management, University of Copenhagen, Copenhagen, Denmark;1. IPMA, Instituto Português do Mar e da Atmosfera, Rua C do Aeroporto, 1749-077 Lisbon, Portugal;2. Centre of Oceanography, Faculty of Science, University of Lisbon, Campo Grande, 1749-016, Lisbon, Portugal;3. CIMAR/CIIMAR — Interdisciplinary Centre of Marine and Environmental Research, Porto, Portugal;4. Department of Geosciences, Environment and Spatial Planning, University of Porto, Porto, Portugal;5. Plymouth Marine Laboratory, Prospect Place, PL1 3DH Plymouth, UK |
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| Abstract: | Hydrographic data from the World Ocean Circulation Experiment (WOCE) and South Atlantic Ventilation Experiment (SAVE) in the region of transition between the Scotia Sea and the Argentine Basin are examined to determine the composition of the deep water from the Southern Ocean that enters the Atlantic, and to describe the pathways of its constituents. The deep current that flows westward against the Falkland Escarpment is formed of several superposed velocity cores that convey waters of different origins: Lower Circumpolar Deep Water (LCDW), Southeast Pacific Deep Water (SPDW), and Weddell Sea Deep Water (WSDW).Different routes followed by the WSDW upstream of, and through, the Georgia Basin, lead to distinctions between the Lower-WSDW (σ4>46.09) and the Upper-WSDW (46.04<σ4 <46.09). The Lower-WSDW flows along the South Sandwich Trench, then cyclonically in the main trough of the Georgia Basin. Although a fraction escapes northward to the Argentine Basin, a comparison of the WOCE data with those from previous programmes shows that this component had disappeared from the southwestern Argentine Basin in 1993/1994. This corroborates previous results using SAVE and pre-SAVE data. A part of the Upper-WSDW, recognizable from different θ–S characteristics, flows through the Scotia Sea, then in the Georgia Basin along the southern front of the Antarctic Circumpolar Current. Northward leakage at this front is expected to feed the Argentine Basin through the northern Georgia Basin. The SPDW is originally found to the south of the Polar Front (PF) in Drake Passage. The northward veering of this front allows this water to cross the North Scotia Ridge at Shag Rocks Passage. It proceeds northward to the Argentine Basin around the Maurice Ewing Bank. The LCDW at the Falkland Escarpment is itself subdivided in two cores, of which only the denser one eventually underrides the North Atlantic Deep Water (NADW) in the Atlantic Ocean. This fraction is from the poleward side of the PF in Drake Passage. It also crosses the North Scotia Ridge at Shag Rocks Passage, then flows over the Falkland Plateau into the Atlantic. The lighter variety, from the northern side of the PF, is thought to cross the North Scotia Ridge at a passage around 55°W. It enters the Argentine Basin in the density range of the NADW. |
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