Abstract
The complex nature of the North Brazil Current (NBC) has lead to various studies regarding its seasonal variations and eddy-shedding regime. Horizon Marine, Inc. has conducted operational analysis of the NBC for the past 8 years, making use of drifting buoys, satellite imagery, and ADCP data. We have validated observations made by previous studies such as references [1–5] during this time period. Energy fluctuations within the NBC Retroflection can create a closed circulation at the point of inception of the North Equatorial Counter Current (NECC). This closed circulation can spin off as it gains momentum to create a separate anticyclonic eddy, known as an NBC ring. Our observations indicate that the NBC Retroflection sheds between 5 and 8 NBC rings over the period of 1 year. These rings vary from 100 to 500 km in diameter and 70 to 200 cms1 in surface intensity. The depth of the coherent velocity structure can vary from 200m to 1000m as described in [1] and [4]. The structure and intensity of each ring varies seasonally as does its migration rate and trajectory. The energy sector offshore Trinidad and Tobago is most strongly impacted by the NBC ring influence on local oceanographie conditions, most critically the vigorous near-surface currents associated with the rings' strong vertically coherent velocity fields. The extent of this influence depends on the NBC ring proximity to the shelf break, the ring swirl velocity, and vertical variation in the ring velocity field. In this study, we quantify characteristic patterns of oceanographie variation imposed by NBC rings observed in our operational dataseis. Of central importance is determining the variations in migration patterns of NBC rings with changing seasonality.
Published Version
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