Quantifying Radiometric Sensitivity to Ranges of CDOM Absorption, Spectral Slope and Phytoplankton Composition in Arctic and sub-Arctic Waters

Optical constituents in Arctic and sub-Arctic environments are highly variable on seasonal, annual, and spatial scales. Absorption due to phytoplankton (a_phy) can vary due to both bloom state and community composition, while absorption due to colored dissolved organic matter (CDOM, a_g) can account for up to two-thirds of non-water light absorption at 440 nm. The impacts of chlorophyll-specific phytoplankton absorption relative to varying phytoplankton composition and varying spectral slope of CDOM (S_g) on the retrieval of a_g from remote sensing reflectance (R_rs) is not well understood in Arctic and sub-Arctic environments. In this study, radiative transfer modeling is utilized to explore sensitivity of R_rs(λ) to ranges of a_g, S_g and a_phy affiliated with specific phytoplankton assemblages and bloom conditions. We focus on quantifying detection improvements of a_g and S_g with anticipated expanded spectral and signal-to-noise capabilities of the PACE mission as well as thresholds of detection for heritage (SeaWiFS), current (MODIS, VIIRS) and future (PACE) sensor capabilities. Particular focus will be given to investigating changes in S_g and its impact on light availability for phytoplankton as it relates to rapid changes currently observed and anticipated in the Arctic and sub-Arctic environment.