Diagnosing large Gulf Stream meanders in the South Atlantic Bight using adjoint sensitivity analysis

Large meanders of the Gulf Stream (GS) are often observed in the South Atlantic Bight (SAB). They lead to significant cross-shelf exchanges of heat, water, nutrients, and strongly impact regional ocean circulation and marine ecosystem. Based on 20+ years satellite sea level data and an edge detection method, we quantify the GS meanders in the SAB, and identified a large GS offshore meander in late 2009. A regional ocean model (based on ROMS) was further developed and used to hindcast this meander event. Close comparisons between simulated and observed sea level, sea surface temperature, ocean transport, and GS positions indicate the model has a good skill reproducing coastal circulation and GS meander during the study period. We further applied ROMS tangent linear adjoint tool to diagnose sensitivity of this large GS meander to local wind forcing, upstream transport, and open ocean eddy activities. Our results show that remote forcings are the dominating factors for generating and maintaining this particular large GS meander.