by Franco, Bárbara Cristie

Abstract (Summary)
The outflow of cold, dense water from the Weddell Sea into the ocean basins tothe north plays a key role in balancing the global heat budget. We estimate thegeostrophic flow patterns in the northwestern Weddell Sea during the BrazilianDOVETAIL 2000 and 2001 austral summer cruises, using box inverse methods appliedto hydrographic data. The analysis is focused on the variations of the deep Weddell Seaoutflow into the Scotia Sea within boxes that bound the main deep gaps over the SouthScotia Ridge. To determine the geostrophic volume transports, in each box mass, saltand heat are conserved within layers that are not in contact with the atmosphere anddefined by neutral surfaces. Implementing the inverse model and using propertyanomaly equations weighted by the flow estimate uncertainty our results are consistentwith those reported in the literature. A new bottom triangle extrapolation method isintroduced, which improves the estimated property fluxes through hydrographicsections. During the austral summer of 2000 the Weddell Sea Deep Water (WSDW)transports 0.01 ± 0.01, 1.15 ± 0.32 and 1.03 ± 0.23 Sv (1Sv = 106 m3.s-1, > 0 isnorthward) over the Philip Passage, Orkney Passage and Bruce Passage, respectively.After extrapolation within bottom triangles these transports are 0.12 ± 0.03, 3.46 ± 1.81and 1.20 ± 2.15 Sv. The hydrographic data reveal distinct oceanographic conditionsover the Philip Passage region with evidence of mesoscale meanders, warmer and saltierWarm Deep Water (WDW) and colder WSDW observed in 2001. In spite of theproperties differences observed the WSDW transport does not present a significantvariation between 2000 and 2001. The WSDW transports 0.012 ± 0.001 Sv and 0.113 ±0.002 Sv when extrapolating in the bottom triangles. The circulation derived from theinversion in the austral summer of 2001 suggests a sharp weakening of the barotropiccyclonic flow in the Powell Basin. The observed weakening may be due to northerlyand northeasterly winds associated to an atmospheric low pressure center located westof the Antarctic Peninsula.
Bibliographical Information:

Advisor:Alberto Ricardo Piola; Carlos Alberto Eiras Garcia; Ricardo Matano; Maurício Magalhães Mata

School:Fundação Universidade Federal do Rio Grande

School Location:Brazil

Source Type:Master's Thesis

Keywords:oceanografia fisica noroeste do mar de weddell água profunda variação fluxo profundo método inverso


Date of Publication:05/02/2006

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