Coastal upwelling in the South Atlantic Bight: A revisit of the 2003 cold event using long term observations and model hindcast solutions

Abstract

Long-term (2002–2008) buoy observations, satellite imagery, and regional ocean circulation hindcast solutions were used to investigate the South Atlantic Bight (SAB) cold event that occurred in summer 2003. Observations confirmed that SAB shelf water temperature during the event was significantly colder than their 7-year (2002–2008) mean states. The cold event consisted of 6 distinctive cold wakes, which were likely related with intra-seasonal oscillations in wind fields. The upwelling index analyses based on both in situ buoy wind and North American Regional Reanalysis (NARR) highlighted that the upwelling favorable winds in 2003 were the strongest and most persistent over the 7-year study period. The regional circulation model hindcast driven by the large scale data assimilative model, NARR surface meteorological forcing and coastal river runoff generally reproduced observed hydrodynamic variability during the event. Further model analyses revealed a close relationship between the cold bottom water intrusion and the Gulf Stream (GS) core intensity and its position relative to the shelf break. Being more intensive and shoreward located, the GS worked in concert with strong upwelling favorable wind field to produce abnormal upwelling in summer 2003.