Gulf Stream variability and a triggering mechanism of its large meander in the South Atlantic Bight

The Gulf Stream (GS) variability has an important impact on coastal circulation, shelf ecosystem, and regional weather and climate systems. Here we focus on the variability of the GS south of Cape Hatteras in the South Atlantic Bight (SAB). Statistical analysis on the 21 year satellite altimetry data reveals that the GS path in the SAB has two patterns: weakly and strongly deflected. The strongly deflected pattern is more likely to occur in winter. Over the last two decades, the largest GS offshore meander occurred in November 2009 to April 2010. Realistic ocean hindcast simulation and adjoint sensitivity analysis are used to investigate the triggering mechanisms for this extreme event. Our analyses show that a net increase of relative vorticity near the Charleston Bump was generated by strong interaction between increased GS velocity and local bathymetry, pushing the GS further offshore by virtue of conserving the potential vorticity. Quantitative vorticity analysis confirms this finding.

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