The North Brazil Current Rings Experiment: Data Analysis and Synthesis

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ABSTRACTPI/Institution: Johns / RSMAS Proposal No: OCE-0241430During 1998-2000 a team of conducted the North Brazil Current Rings Experiment (NBCRE). This program obtained the first comprehensive observations of the North Brazil Current (NBC) retroflection, the NBC ring formation process, and the physical structure and properties of NBC rings as they translate northwestward along the western boundary. The goal of the NBCRE is to understand the process of NBC ring generation and to quantify the role of NBC rings in cross-equatorial and cross-gyre transport within the Atlantic meridional overturning circulation (MOC). This proposal requests support for analysis and synthesis of the data collected during NBCRE program. The remaining analysis and synthesis tasks have been organized among the principal investigators and this proposal requests support for the Miami PI's to complete the synthesis of the shipboard ADCP data and CTD/LADCP station data collected on four cruises to the region as well as data from current meter moorings and inverted echo sounders deployed in the area of NBC ring formation. Results from satellite altimetry and surface drifters and floats available in the region (including some launched by our WHOI colleagues as part of the project), and model results from MICOM simulations, will be also be included in the collaborative analysis. The specific objectives of this proposal are to: document the 3-D structure of the NBC retroflection and the large- scale western boundary current system observed during the four research cruises, provide a thorough description of the temporal variability of the NBC retroflection and the physical processes involved in the separation of rings from the retroflection, including upstream NBC variability and possible remote influences, and determine the physical structure and watermass properties of the rings after separation from the NBC and the volume of South Atlantic water they trap and transport northward into the subtropical North Atlantic. Once completed, this synthesis will provide a vastly improved understanding of the phenomenology of NBC ring shedding and the significance of these features to the North Atlantic circulation. In addition to increasing our physical knowledge of the rings, the synthesis will serve as a baseline for future model evaluations and model-based process studies in the region.