Global distribution and dynamics of colored dissolved and detrital organic materials

Abstract

Colored dissolved organic matter (CDOM), also referred to as gelbstoff, gilvin, or yellow matter, has long been known to be an important component of the optical properties of coastal and estuarine environments. However, an understanding of the processes regulating its global distribution and variability, its relationship to the total pool of dissolved organic carbon (DOC), and its influence on light availability remain largely unexplored. Satellite imagery from the Sea‐viewing Wide Field‐of‐view Sensor (SeaWiFS) is used to characterize the global distribution of light absorption due to colored detrital and dissolved materials (CDM). The quantity CDM is considered as it is not yet possible to differentiate CDOM and detrital particulate absorption from ocean color spectra on a routine basis. Nonetheless, analysis of an extensive field data set indicates that detrital particulates make only a small contribution to CDM. A comparison of coincident field observations of CDM with SeaWiFS retrievals shows good agreement, indicating that the present procedures perform well. To first order, the basin‐scale CDM distribution reflects patterns of wind‐driven vertical circulation of the gyres modulated by a meridional trend of increasing CDM toward higher latitudes. The global CDM distribution appears regulated by a coupling of biological, photochemical, and physical oceanographic processes all acting on a local scale, and greater than 50% of blue light absorption is controlled by CDM. Significant differences in both CDM concentration and its contribution to blue light absorption are found spatially among the major ocean basins and temporally on variety of timescales. Significant impacts of riverine discharges can be discerned, although their effects are largely localized. Basin‐scale distributions of CDM and DOC are largely unrelated, indicating that CDM is a small and highly variable fraction of the global DOC pool. This first view of the global CDM distribution opens many new doors for the quantification of global marine photoprocesses using satellite ocean color data.