Distributions and characteristics of colored dissolved organic matter in the Western Arctic Ocean

Terrigenous dissolved organic matter (DOM) is continuously discharged by rivers into the ocean, yet its distribution and reactivity within ocean basins remain poorly defined. With high concentrations of terrestrial DOM in arctic rivers and a disproportionate share of global riverine discharge on a volume basis to the Arctic Ocean, the influence of terrigenous DOM on marine carbon budgets and the global carbon cycle can be significant. In this paper, we report the detection of terrestrial DOM using optical properties of surface waters in the Western Arctic Ocean. The distribution of absorption and fluorescence of colored dissolved organic matter (C-DOM) and dissolved organic carbon (DOC) were recorded. Mixing of C-DOM was conservative at low and mid-salinity (S>25‰), indicating a terrestrial origin for this material and the absence of strong in situ sources and sinks. However, at higher salinities (>25‰), C-DOM distribution was highly scattered due to the mixing of water masses of statistically different optical properties. Higher absorption coefficients and C-DOM and DOC concentrations reflect the higher contribution of terrigenous DOM. The region most influenced by land-derived DOM is the Mackenzie Shelf where the 3D excitation/emission matrix spectra show a strong signature of continental inputs. Furthermore, the absence of a typical marine DOM signal indicates that a terrigenous component dominated C-DOM composition throughout the entire Western Arctic Ocean.