Challenges to validating satellite POC products

Ivona Cetinic, University of Maine, ivona.cetinic@maine.edu (Presenter)
Mary Jane Perry, University of Maine, perrymj@maine.edu
Nathan Briggs, University of Maine, nathan.m.briggs@maine.edu
Emily Kallin, University of Maine, emily.briggs@maine.edu

The co-variability of optical scattering coefficients and particulate organic carbon (POC) provides a basis for estimating POC from ocean color satellite measurements. In-water measurement of POC optical proxies has the potential to enable validation of satellite POC products on the requisite spatial and temporal scales that are now impossible to obtain with traditional, and expensive, discrete water sampling and chemical analysis methods. However a consistent measurement protocol is required to bring this potential to fruition. During the North Atlantic Bloom experiment of 2008 (NAB08), we accrued a large dataset consisting of 321 POC samples and simultaneous particulate attenuation, c_p, and particulate backscattering, b_bp, coefficients. Scrupulous attention to sampling details, use of multiple types of POC blanks and 232 actual blanks, cross-calibration of optical instruments, and parallel measurements of other biogeochemical parameters facilitated distinction between natural (i.e., particle composition) and methodological sources of variability, allowing us to constrain uncertainties in the POC proxies. We found that change in surface phytoplankton community composition was reflected in only a small change in POC/c_p , and no change in POC/b_bp. Both POC/b_bp and c_p/b_bp decreased with depth, suggesting changes in b_bp with depth, perhaps as a function of changing particle composition. From a detailed analysis of previously published POC scattering proxies, we found it difficult to separate effects of methodologies vs. particle composition on variability in these proxies. We suggest that rigorous examinations with standard protocols and in waters with a diversity of particle types are required for evaluating and validating satellite POC products.

Presentation Type:  Poster

Session:  Science in Support of Decision Making   (Wed 10:00 AM)

Associated Project(s): 

• Perry, Mary: Estimating particle size in the ocean from high-frequency variability in in-situ optics ...details
• Perry, Mary: Reducing uncertainty in the marine carbon cycle by coupling satellite and in-water robotic measurements ...details

Poster Location ID: 129