Temporal and spatial variability of Chl- a and SST on the South Atlantic Bight: Revisiting with cloud-free reconstructions of MODIS satellite imagery

Abstract

Daily, cloud-free data interpolating empirical orthogonal function (DINEOF) reconstructions of sea-surface temperature (SST) and chlorophyll (Chl- a) satellite imagery are compiled into monthly mean images for a six-year period (2003–2008) and used to identify their spatial and temporal variability on the South Atlantic Bight. Monthly-mean SST has the highest variability on the inner-shelf, decreasing seaward approaching the more stable temperatures of the Gulf Stream (GS). Monthly-mean Chl- a concentrations are similarly highest on the inner shelf throughout the year and decrease cross-shelf toward the nutrient depleted open ocean. Empirical orthogonal function (EOF) analyses on SST and Chl- a show a clear seasonal cycle in their 1st mode of variability, with SST lagging behind Chl- a by approximately one month. The 1st EOF modes account for 95.8% and 46.4% variance of SST and Chl- a, respectively. Chl- a EOF mode 1 in particular shows a highly regionalized spatial pattern with values on the central SAB clearly out of phase with the southern and northern SAB. This regional difference is likely a result of shelf geometry and stratification, which modulate GS influence on the shelf. SST EOF mode 2 exhibits a seasonal cycle as well, which previous studies have shown to be a function of local wind. Chl- a EOF mode 2 is well correlated with the cumulative river transport onto the SAB, but accounts for a relatively small 10.8% of Chl- a variability.