Characterizing the South Atlantic Bight seasonal variability and cold-water event in 2003 using a daily cloud-free SST and chlorophyll analysis.

Abstract

Concurrent MODIS sea surface temperature (SST) and chlorophyll-a (Chl-a) data are used with a new technique  Data Interpolating Empirical Orthogonal Function (DINEOF) method  to produce daily, 4-km, cloud-free SST and Chl-a analyses for the South Atlantic Bight in 2003. Comparisons between SST analysis and in situ buoy temperature demonstrate DINEOF’s utility. To quantify connections between surface wind, SST and Chl-a variation, Empirical Orthogonal Function (EOF) analysis is applied to North American Regional Reanalysis winds, cloud-free DINEOF SST and Chl-a analyses. Wind EOF modes highlight upwelling winds from June to September. While the first SST mode represents seasonal heat flux variations, the second SST mode shows a direct response to upwelling winds with an abrupt drop in SST. The top two Chl-a EOF modes show less connection with wind, suggesting more subsurface Chl-a and nutrient observations are needed to quantify its relation with surface wind. An additional study is performed on a larger DINEOF SST and Chlorophyll-a dataset including 2003-2007 for an identical spatial domain. This dataset puts the 2003 cold event in the context of a long-term dataset. An analysis of the Gulf Stream summer position is performed using the 0.25 mg/m3 Chl-a contour line to define the Gulf Stream front. When compared to 2004-2007, 2003 has an anomalous offshore position.