Colin A Stedmon

and 10 more

The Arctic Ocean receives a large loading of dissolved organic matter (DOM) from its catchment and shelf sediments, which can be traced across much of the basin. This signature can be used as a tracer of water mass circulation. On the shelf seas, the combination of freshwater loading from rivers and ice formation modify water mass densities and mixing considerably. These waters are the source of the halocline layer that covers much of the Arctic ocean. Our knowledge of the origins, formation and maintenance of the halocline has mostly arisen from CTD profiles and chemical tracers such as oxygen stable isotopes and inorganic nutrients, but the halocline also contains elevated levels of DOM (DOM). Here we demonstrate how this can be used as a tracer and help improve our understanding of ocean circulation. DOM fluoresce can be measured using in-situ fluorometers and mounted on autonomous platforms these can provide high spatial resolution measurements. Here we present data derived from several Ice Tethered Profilers. The data offer a unique spatial coverage of the distribution of DOM in the surface 800m below Arctic ice. Water mass analysis using temperature, salinity and DOM fluorescence, clearly distinguishs the halocline contribution of Siberian terrestrial DOM and marine DOM from the Chuckchi shelf. The findings offer a new approach to trace the distribution of Pacific waters and its export from the Arctic Ocean. Our results indicate the potential to extend the approach to fraction freshwater contributions from, sea ice melt, riverine discharge and Pacific water.