Towards an integrated understanding of buoyancy fluxes, bio-optics, and coastal circulation: Results from the interdisciplinary PlumeCASE experiment

For two weeks during June 2015, an array of current meters and string moorings were deployed over the Louisiana continental shelf. Moored instrument deployments were supplemented with ship station sampling and towed platform (ScanFish) surveys to assess the physical, bio-optical, and biogeochemical state of our dedicated operations area during the Buoyancy Plume Modulation of Coastal Air-Sea Exchange (PlumeCASE) experiment. An anomalous wind event during the experiment provided an opportunity to contrast surface stratified/non-stratified conditions over the shelf in response to wind forcing and solar heating. During stratification, surface currents were characterized by large amplitude, diurnal cross-shelf components. In particular, the offshore moorings captured the apparent diurnal expansion and contraction of the Mississippi River Plume edge in the upper 5-meters of the water column as well as an amplified diurnal surface temperature cycle indicative of enhanced bio-optical heat trapping effects within the plume. Whereas the colder near-bottom waters bore distinct optical and biological signatures as well as substantial cross-shelf flow velocities. Thusly, we observed a 3-layered biophysical system with distinct kinematic and bio-optical properties endemic to each density transition. We also present remote sensing data and preliminary sensitivity results from an integrated air-sea-biology numerical modeling system (based on COAMPS) that collectively provide insight into our observational analysis.