Assessment of particulate absorption properties in the southeastern Bering Sea from in-situ and remote sensing data

Particulate absorption (aP(λ)) including phytoplankton (aPHY(λ)) and non-algal particles (NAP) (a NAP(λ)) were measured in southeastern Bering Sea during a cruise in July 2008. This study analyzes the aP(λ) properties through in-situ and quasi analytical algorithm (QAA) derived ocean color satellite Medium Resolution Imaging spectrometer (MERIS) and Moderate resolution Imaging Spectroradiometer (MODIS) observations. We found that the a P(λ) and aPHY(λ) correlated well with chlorophyll-a and were lower as a function of chlorophyll-a as compared to low latitudes. The specific phytoplankton absorption (a* PHY(λ)) showed more variability in the blue as compared to the red part of the spectrum indicating pigment packaging and/or change in pigment composition. The remote sensing reflectance (Rrs(λ)) showed significant variability in spectral shape and magnitude which was consistent with the variable total absorption minus pure water absorption (aT-W(λ)) spectra observed in the study area. Simple satellite retrieved R rs(λ) ratios were related to in-situ aPHY(λ) and aDGλ) by applying an inverse power fit; Rrs(490)/Rrs(510) gave the best results for aPHY(443) and aDG(443) (R2-0.80 and 0.75) respectively. The match-ups of in-situ and MERIS retrieved a PHY(λ) and NAP plus colored dissolved organic matter (a DG(λ)) using QAA after log-transformation showed reasonable agreement with R2 of 0.71 and 0.61 and RMSE of 0.316 and 0.391 at 443 nm, respectively. Although the QAA derived aPHY(λ) and a DG(λ) from MERIS overestimated and underestimated, respectively the in-situ measurements at all wavelengths, the match-up analysis was encouraging. © 2010 Society of Photo-Optical Instrumentation Engineers.