Characterizing CDOM Spectral Variability Across Diverse Regions and Spectral Ranges

Abstract Satellite remote sensing of colored dissolved organic matter (CDOM) has focused on CDOM absorption ( a CDOM ) at a reference wavelength, as its magnitude provides insight into the underwater light field and large‐scale biogeochemical processes. CDOM spectral slope, S CDOM , has been treated as a constant or semiconstant parameter in satellite retrievals of a CDOM despite significant regional and temporal variabilities. S CDOM and other optical metrics provide insights into CDOM composition, processing, food web dynamics, and carbon cycling. To date, much of this work relies on fluorescence techniques or a CDOM in spectral ranges unavailable to current and planned satellite sensors (e.g., <300 nm). In preparation for anticipated future hyperspectral satellite missions, we take the first step here of exploring global variability in S CDOM and fit deviations in the a CDOM spectra using the recently proposed Gaussian decomposition method. From this, we investigate if global variability in retrieved S CDOM and Gaussian components is significant and regionally distinct. We iteratively decreased the spectral range considered and analyzed the number, location, and magnitude of fitted Gaussian components to understand if a reduced spectral range impacts information obtained within a common spectral window. We compared the fitted slope from the Gaussian decomposition method to absorption‐based indices that indicate CDOM composition to determine the ability of satellite‐derived slope to inform the analysis and modeling of large‐scale biogeochemical processes. Finally, we present implications of the observed variability for remote sensing of CDOM characteristics via S CDOM .