Southeast Coastal Ocean Report 36 The temporal evolution of the low salinity feature on the SAB shelf in 2003 was documented through a combination of ocean color satellite imagery, time series measurements at the offshore Navy towers (SABSOON), and cross-shelf CTD transects conducted from the SkIO research vessel, the R/V Savannah.  The SE rivers contain relatively high concentrations of colored dissolved organic matter (CDOM; some are "blackwater" rivers).  The strong absorption by CDOM in the violet-to-blue region of the visible spectrum provides an optical signal that can be detected in ocean color satellite imagery.  Figure 4b.4 shows examples of SeaWiFS "acdm" imagery (absorption by colored detrital material at 443 nm; operationally the sum of absorption by CDOM and non-living particulate organic matter) from the winter and spring of 2003.  Based on analyses of samples from a number of cruises, seaward of the turbid coastal zone, most of the "acdm" signal appears to be contributed by CDOM.  While this cannot be considered to be a conservative tracer, the "acdm" signal does indicate the distribution of lower salinity water masses on the shelf.  Confined to the near-shore zone in winter, the area of high "acdm" expanded during spring until it extended seaward to the shelf break.    Hydrographic surveys conducted during the spring of 2003 on the Georgia shelf (most being SE transects from Wassaw Sound Georgia, adjacent to SkIO) showed a transition from a vertically mixed water column with strong cross-shelf salinity gradient in late April to a vertically stratified water column, with ~8 m thick low-salinity surface layer, across the mid-shelf in early May (Fig. 4b.5).  Time series measurements at the R2 platform (see Fig. 4b.4 for location) document the development of salinity stratification at this mid-shelf location (Fig. 4b.6).  Seasonal warming of the surface layer in late spring further strengthened mid-shelf stratification.  The vertically stratified salinity structure persisted into mid-June at the R2 platform.  For the remainder of the summer 2003, the Fig. 4b.4.  SeaWiFS "acdm" imagery from the winter-spring of 2003.  Note the color scale for estimated absorption (443 nm) is logarithmic (3-decades).  The river-derived CDOM bleaches with time on the shelf, thus the lower signal in May was likely due to a combination of signal degradation and dilution with sea water.    The location of the R2 platform is indicated by the arrow in the 31 May panel.