Tim Cowles, Jack Barth, Jim Richman; Oregon State University

"Mesoscale Physical and Biological Processes at the Polar Front"

We will investigate the mesoscale dynamics during two cruises of the Polar Front study (Oct. 97, Jan. 98), using an instrumented towed vehicle (SeaSoar) to resolve the physical and biological fields over horizontal spatial scales of 1150 km, with 2 m vertical resolution within the upper 400 m. Our towed instrumentation will document the vertical and horizontal scales of both physical (T, S, pressure, PAR) and biological parameters (spectral absorption, spectral beam attenuation, spectral fluorescence). The high resolution, quasisynoptic density and velocity data from these SeaSoar/ADCP surveys will be used to map the thermohaline structure within the Polar Front region, identify water mass distributions, map the properties and depth distribution of the surface mixed layer, establish the baroclinic flow shear and map the directly measured absolute velocity. High resolution vertical sections across the frontal region will be examined for evidence of subduction of water parcels. Observed mesoscale, submesoscale and finescale variations in the physical fields will be related to observed variations in the biological fields defined by the biooptical instrumentation on the SeaSoar. Time and funding permitting, we will use a profiling biooptical system during the discrete station sampling portion of each cruise to resolve finescale vertical structure. This freefall CTD package has sensors for T, S, O2, downwelling and upwelling spectral irradiance, multispectral absorption and beam attenuation, and multiexcitation spectral fluorescence. Discrete samples will be processed to determine floristic composition of phytoplankton and microzooplankton (preserved reference samples), as well as pigment composition of particulates using HPLC. We expect to interact with all investigators interested in the relationship of single station data to regional processes.