Deep Western Boundary Current transport variability in the South Atlantic: preliminary results from a pilot array at 34.5° S

[摘要] The first direct estimates of the temporal variability of the absolutetransport in the Deep Western Boundary Current (DWBC) at 34.5°S inthe South Atlantic Ocean are obtained using just under one year of data froma line of four pressure-equipped inverted echo sounders. Hydrographicsections collected in 2009 and 2010 confirm, based on neutral density,temperature, salinity, and oxygen values, the presence of the DWBC, one ofthe main deep pathways of the Meridional Overturning Circulation. Both datasets indicate that the DWBC reconstitutes itself after breaking into eddiesin the western sub-tropical Atlantic near 8° S. The amplitude andspectral character of the DWBC transport variability are comparable withthose observed in the North Atlantic, where longer records exist, with theDWBC at 34.5°S exhibiting a transport standard deviation of 25 Svand variations of ∼ 40 Sv occurring within periods as short as a fewdays. There is little indication of an annual cycle in the DWBC transports,although the observational records are too short to be definitive. A MonteCarlo-style analysis using 27 yr of model output from the same location asthe observations indicates that about 48–60 months of data will be requiredto fully assess the deep transport variability. The model suggests thepresence of an annual cycle in DWBC transport, however its statisticalsignificance with even 27 yr of model output is low, suggesting thatseasonal variations in the model are weak.

[学科分类] 海洋学与技术