The role of the Brazil-Malvinas confluence on regional mesoscale dynamics and climate

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)

First Committee Member

Donald B. Olson - Committee Chair


Investigation of the role of the southwestern South Atlantic (SWA) on regional mesoscale dynamics and short-term climate variability in the southeastern South American (SESA) region has been conducted. The region of study, which extends roughly west of 45°W and from 25°S to 50°S, comprises part of Argentina, southern Brazil, Uruguay, and the Brazil-Malvinas Confluence extension.For the first time to our knowledge, a connection linking the mesoscale dynamics and the regional climate to the large scale flow in the SWA is established. This is also one of the most significant mid- to high-latitude climate anomaly mechanisms that have been identified to date. As a consequence of this connection, densely populated areas in the SESA region are economically affected. The local fish resources and agricultural activities are, among others, severely impacted. The compilation of our results shows that when the Brazil and Malvinas currents are relatively close to each other, the meridional time mean latitude of separation of the Brazil Current becomes totally dependent on the Malvinas upstream behavior. Variations in the distance between the two currents seem also to impact the rate of formation of warm, anticyclonic rings released into the subpolar region and the poleward extension of the Brazil Current. In terms of the Brazil-Malvinas Confluence, besides the association between ring formation and width of the Confluence, the results indicate that the coupling between Malvinas and Brazil currents can severely affect the local physical and biological dynamics upstream of the Confluence.Squared coherency computations between the Brazil and Malvinas currents, and precipitation over Uruguay show that the position of the Confluence is associated with rainfall anomalies on annual time scales. The analysis also suggests that SST anomalies of the subantarctic sector force the local climate and river discharge in the SESA region mostly on relatively long time scales. Although more data is needed to confirm these conclusions, they strongly suggest the importance of the subantarctic sector in regulating the geometry of the Confluence and the regional climate at least on ENSO time scales.


Physical Oceanography

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