Insights into Water Mass Origins in the Central Arctic Ocean from
in-situ Dissolved Organic Matter Fluorescence.
The Arctic Ocean receives a large supply of dissolved organic matter
(DOM) from its catchment and shelf sediments, which can be traced across
much of the basin’s upper waters. This signature can potentially be used
as a tracer. On the shelf, the combination of river discharge and
sea-ice formation, modifies water densities and mixing considerably.
These waters are a source of the halocline layer that covers much of the
Arctic Ocean, but also contain elevated levels of DOM. Here we
demonstrate how this can be used as a supplementary tracer and
contribute to evaluating ocean circulation in the Arctic. A fraction of
the organic compounds that DOM consists of fluoresce and can be measured
using in-situ fluorometers. When deployed on autonomous platforms these
provide high temporal and spatial resolution measurements over long
periods. The results of an analysis of data derived from several Ice
Tethered Profilers (ITPs) offer a unique spatial coverage of the
distribution of DOM in the surface 800m below Arctic sea-ice. Water mass
analysis using temperature, salinity and DOM fluorescence, can clearly
distinguish between the contribution of Siberian terrestrial DOM and
marine DOM from the Chukchi shelf to the waters of the halocline. 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 separate freshwater contributions
from, sea-ice melt, riverine discharge and the Pacific Ocean.