Near-surface eddy dynamics in the Southern Ocean revealed by drifter observations
Marilisa Trani, Pierpaolo Falco, Enrico Zambianchi
University of Siena, Siena, Italy
(Abstract received 08/14/2009 for session A)
ABSTRACT
Observations obtained from drifters represent a very useful dataset to analyse eddy components of the velocity field because they may describe turbulence at different scales while providing a synoptic coverage of the investigated area. In the Southern Ocean the eddy field plays a central role in the dynamical and thermodynamical balance of the circulation. Estimates of the eddy heat and momentum fluxes are carried out in this work using data from WOCE-SVP drifters along their pathways approximately south of 40°S from 1995 to 2007. Variance ellipses, EKE, momentum and heat fluxes have been calculated using the pseudoeulerian method. Results show patterns in good agreement with those present in literature, although there are some quantitative differences. A rearrangement of the data has been carried out using isolines of constant absolute dynamic height as bin limits. This has been done in order to have bins which separate areas with similar dynamical characteristics.
Maxima of the eddy momentum flux are observed near the major topographic features where the mean field there is consistently deviated to the north (south) with a positive (negative) value of the flux. Sea Suface temperature variability is higher at lower latitudes, in particular in the Agulhas retroflection and off the east coast of south America at the Brazil-Malvinas confluence where water masses with strongly contrasting characteristics meet each other. Distributions of vertically integrated eddy heat transports are also presented and discussed.
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