The conservative behavior of dissolved organic carbon in surface waters of the southern Chukchi Sea, Arctic Ocean, during early summer.

Kazuki Tanaka,Toru Hirawake,Youhei Yamashita,Yoshiko Kondo,Kenshi Kuma,Atsushi Ooki,Jun Nishioka,Nobuyuki Takesue

doi:10.1038/srep34123

Abstract

The spatial distribution of dissolved organic carbon (DOC) concentrations and the optical properties of dissolved organic matter (DOM) determined by ultraviolet-visible absorbance and fluorescence spectroscopy were measured in surface waters of the southern Chukchi Sea, western Arctic Ocean, during the early summer of 2013. Neither the DOC concentration nor the optical parameters of the DOM correlated with salinity. Principal component analysis using the DOM optical parameters clearly separated the DOM sources. A significant linear relationship was evident between the DOC and the principal component score for specific water masses, indicating that a high DOC level was related to a terrigenous source, whereas a low DOC level was related to a marine source. Relationships between the DOC and the principal component scores of the surface waters of the southern Chukchi Sea implied that the major factor controlling the distribution of DOC concentrations was the mixing of plural water masses rather than local production and degradation.

Highlights

The spatial distribution of dissolved organic carbon (DOC) concentrations and the optical properties of dissolved organic matter (DOM) determined by ultraviolet-visible absorbance and fluorescence spectroscopy were measured in surface waters of the southern Chukchi Sea, western Arctic Ocean, during the early summer of 2013
Some studies have reported a half-life of terrigenous DOC of < 3 years and < 7 years for the Siberian Shelf and the Beaufort Gyre, respectively[8,9], carbon-normalized yields of lignin phenols have indicated that 14–24% of the DOC throughout the upper Arctic Ocean is of terrestrial origin[10], implying various reactivities of terrigenous DOM
The Anadyr water (AW) was distinguished from the Bering shelf water (BSW) by temperature and salinity (Table 1; Supplementary Fig. S1; Fig. 1) because the AW can be characterized as cooler and more saline compared to the BSW23,24

Summary

Results and Discussion

Water masses in the southern Chukchi Sea. In the early summer of 2013, the warmer, less saline, lower nutrient concentration ACW23,24, known as the Eastern Chukchi Summer Water (ECSW)[20], was distributed to the north of Cape Lisburne (Table 1; Supplementary Fig. S1; Fig. 1). The relationship showed that high levels of DOC were related to terrigenous characteristics, whereas low levels of DOC were related to marine characteristics This observation implies that the major factor controlling the distributions of the DOC concentration and DOM quality in other water masses that could not be identified from the physicochemical parameters (Fig. 1) can be evaluated from the linear relationship. Intervals, indicating that a major factor controlling the distribution of the DOC concentration and DOM quality was the mixing of specific water masses, namely, the ACW, AW, BSW, PWW, and sea-ice melt water, in the surface waters of the southern Chukchi Sea during the early summer of 2013. The application of the approach used in this study to evaluate the conservativeness of DOM in other shelf regions/basins and other seasons could be helpful to clarify the dynamics of DOM in the Arctic Ocean

Methods

Author Contributions

Additional Information