Phinney, D. A.. Bigelow Laboratory for Ocean Sciences, dphinney@bigelow.org
Yentsch, C. A.. Bigelow Laboratory for Ocean Sciences, csyentsch@bigelow.org

 
PARTITIONED ABSORPTION IN CASE 2 WATERS OF THE GULF OF MAINE - EFFECT OF TOTAL SUSPENDED SOLIDS AND GELBSTOFF ON REMOTE SENSING REFLECTANCE
 
Measurements of multispectral remote sensing reflectance and partitioned absorption by particles, phytoplankton, detritus and gelbstoff (CDOM or yellow substances) were measured using a surface reflectance buoy, absorption meter and spectrophotometric methods on eleven cruises throughout the Gulf of Maine and Georges Bank since 1995. Our goal has been to improve the definition of Case 1 and Case 2 waters based on mass units of the three major groups of absorbing compounds such that appropriate algorithms can be applied to remote sensing data and, hence, improve the accuracy of pigment retrievals in Case 2 waters. The cruises were sponsored by the Regional Marine Research Program for the Gulf of Maine, NOAA's Coastal Oceans Program, DEPSCoR and NASA's SeaWiFS Project, and combined, provide excellent seasonal and regional coverage. Companion measurements of chlorophyll, total suspended solids (TSS) and hydrographic parameters are included in the dataset. Absorption coefficients (total non-water, particulate and gelbstoff) measured by the absorption meter compared well with spectrophotometric measurements obtained by the filter pad technique and 0.2 micron filtered samples in 10cm cuvettes. Band ratios of remote sensing reflectance as a function of pigment concentrations to 6 ug/L fell into two groups: 1) offshore Case 1 waters where TSS was <1 mg/L and gelbstoff absorption at 412nm was 0.1 to 1 (m-1) and 2) coastal Case 2 waters where TSS was >1 mg/L and ay412 was 0.3 to 3 (m-1). The more important determinant was TSS concentration, due to the increase in scattering compared to absorption at these stations. While TSS concentrations did not covary with pigment concentrations, TSS did covary with ay412 such that the problem of competitive absorption in the blue wavelength region by three groups of compounds may be reduced to two groups in Case 2 waters of the Gulf of Maine, greatly simplifying remote sensing algorithms in this region.
 
Day: Thursday, Feb. 4
Time: 04:00 - 04:15pm
Location: Sweeney Center
 
Code: CS61TH0400S