Analyses of bio-optical variability related to physical processes on the southern New England continental shelf: July 1996--June 1997

High-resolution time series of physical and bio-optical data were obtained using moored and bottom-mounted instruments during the Coastal Mixing and Optics (CMO) experiment from July 1996--June 1997 to study the relationship between mixing and the distribution of optical properties on the southern New England continental shelf (∼70 m water depth). A previously published spectral absorption model was employed with time series of spectral absorption data to separate total absorption into absorption by water, phytoplankton, detritus, and gelbstoff. Thus, temporal variability and the vertical distributions and concentrations of each component of absorption were examined. The model was validated by comparing its results against coincident in vivo absorption coefficients derived from discrete bottle samples.; The most prominent physical and bio-optical signals observed during the experiment were associated with the seasonal variability. However, several important events interrupted the seasonal cycle. These episodic events appear to have had a great impact on biogenic and non-biogenic matter. Hurricanes Edouard and Hortense passed near the CMO site, resulting in reduced stratification of the water column, particle redistribution, and sediment resuspension. The sediment resuspension processes associated with the two hurricanes are shown to differ primarily because of the separation distances between the eyes of the hurricanes and the observational site. The sediment resuspension processes were tested using a one-dimensional turbulence closure model with a simple suspended particulate matter (SPM) module. Changing hydrographic conditions that resulted from the influence of several water mass intrusions greatly affected particle concentration on time scales of days to several weeks. The bottom boundary layer had an influence on particle movement in the water column and along the seafloor. The results suggest that there is likely considerable interannual variability in both the physics and bio-optics because of active and diverse physical forcing. This experiment also sets the context for comparing our coastal ocean results with previous open ocean findings. Important differences arise because of coastal bottom boundary layer effects, large-scale water mass intrusions, and the relatively greater role of tides on the shelf. Time scales of optical variability are thus shorter for the coastal environment.