Interannual Variability of Fluorescent Dissolved Organic Matter Composition in the Canada Basin, Arctic Ocean From 2007 to 2017

Abstract

AbstractThe interannual variability in fluorescent dissolved organic matter (FDOM) was assessed in the Pacific‐ and Atlantic‐derived halocline, and Atlantic waters (AWs) of the Canada Basin during late summer/early fall expeditions in 2007–2017. Fluorescence spectroscopy excitation‐emission matrices coupled with parallel factor analysis were used to validate a seven‐component model. During the 11 years, humic‐like intensities increased by 0.0002–0.0006 r.u. (Raman unit) (p < 0.05) with greater annual rates of change in shallower waters (i.e., Pacific summer water) than in deeper waters (i.e., AWs). No significant temporal trends were observed for protein‐like intensities in any water layer (p > 0.05) due to the labile nature of these components. The increases in humic‐like fluorescence intensities were likely the results of changes in Bering Strait inflow and its modification over the Chukchi Shelf and/or the accumulation of freshwater under anticyclonic wind forcing in the Beaufort gyre. This 11‐year late summer/early fall survey shows the first evidence of changes in FDOM composition in the halocline of the Arctic Ocean basin.