2004 LOM Workshop

Wednesday 9:00 - 9:20 a.m.

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A model study of the South Atlantic Ocean response to an anomalous heat flux forcing

Carlos Lentini, Reindert Haarsma, Edmo Campos, and Rainer Bleck
Instituto Oceanografico da Universidade de Sao Paulo
lentini@io.usp.br

ABSTRACT

An isopycnal coordinate ocean model coupled to an atmospheric model (SPEEDY-MICOM) has been used to investigate the response of this coupled system forced with anomalous heat fluxes on interannual time scales. The main focus of this work is to look for possible oceanic pathways linking the subtropical to the tropical region, as well as the role played by wave processes on propagating such anomalies. The model domain covers the area between 20N-45S and 65W-20E. The coupled model is spun up for the first 20 years before the atmospheric anomalous surface heat forcing is introduced. The ocean model is forced by heat flux anomalies imposed by the atmosphere which have the same spatial pattern of the subtropical South Atlantic dipole (Sterl and Hazeleger, 2003). SPEEDY-MICOM is forced by this dipole for 1 year. After that, the coupled system is free to evolve for the following 20 years. Ensemble means of forced and non-forced experiments are the basis of our results. Preliminary results show that advection by the mean flow and Rossby Wave dynamics are the two main ways of propagating the imposed anomalies away from its origin toward the South American east coast. Thermal subsurface anomalies are advected within the subtropical South Atlantic gyre by the mean flow, reaching the South American east coast in 4-5 years. No clear evidence of subsurface pathways linking the subtropical to the tropical region has been observed, as post-generated subsurface anomalies stayed within the subtropical gyre for the period of study. Westward propagating Rossby Waves not only introduce circulation anomalies to the mean flow, but they also seem to strongly influence the evolution of the intensity and the shape of the subsurface anomalies.

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LOM Users' Workshop, February 9-11, 2004