Linkages between the circulation and distribution of dissolved organic matter in the White Sea, Arctic Ocean. (15th May 2016)

• Record Type: Journal Article
• Authors: Pavlov, Alexey K.; Stedmon, Colin A.; Semushin, Andrey V.; Martma, Tõnu; Ivanov, Boris V.; Kowalczuk, Piotr; Granskog, Mats A.
• Is Part Of: Continental shelf research. Volume 119(2016)
• Page Start: 1
• Page End: 13
• Publication Date: 2016-05-15
• Subjects: Colored dissolved organic matter -- Dissolved organic carbon -- White Sea -- Arctic Ocean -- Terrestrial runoff; Continental shelf -- Periodicals; Submarine geology -- Periodicals; 551.41
• DOI: 10.1016/j.csr.2016.03.004
• Languages: English
• ISSNs: 0278-4343

Abstract

Abstract: The White Sea is a semi-enclosed Arctic marginal sea receiving a significant loading of freshwater (225–231 km 3 yr −1 equaling an annual runoff yield of 2.5 m) and dissolved organic matter (DOM) from river run-off. We report discharge weighed values of stable oxygen isotope ratios (δ 18 O) of −14.0‰ in Northern Dvina river for the period 10 May–12 October 2012. We found a significant linear relationship between salinity (S) and δ 18 O (δ 18 O=−17.66±0.58+0.52±0.02×S; R 2 =0.96, N=162), which indicates a dominant contribution of river water to the freshwater budget and little influence of sea ice formation or melt. No apparent brine additions from sea-ice formation is evident in the White Sea deep waters as seen from a joint analysis of temperature (T), S, δ 18 O and aCDOM (350) data, confirming previous suggestions about strong tidal induced vertical mixing in winter being the likely source of the deep waters. We investigated properties and distribution of colored dissolved organic matter (CDOM) and dissolved organic carbon (DOC) in the White Sea basin and coastal areas in summer. We found contrasting DOM properties in the inflowing Barents Sea waters and White Sea waters influenced by terrestrial runoff. Values of absorption by CDOM at 350 nm ( a CDOM (350)) and DOC (exceeding 10 m −1 and 550 µmol l −1, respectively) in surface waters of the White Sea basin are higher compared to other river-influenced coastal Arctic domains. Linear relationship between S and CDOM absorption, and S and DOC (DOC=959.21±52.99–25.80±1.79×S; R 2 =0.85; N=154) concentrations suggests conservative mixing of DOM in the White Sea. The strongest linear correlation between CDOM absorption and DOC was found in the ultraviolet (DOC=56.31±2.76+9.13±0.15×aCDOM (254); R 2 =0.99; N=155), which provides an easy and robust tool to trace DOC using CDOM absorption measurements as well as remote sensing algorithms. Deviations from this linear relationship in surface waters likely indicate contribution from different rivers along the coast of the White Sea. Characteristics of CDOM further indicate that there is limited removal or change in the DOM pool before it exits to the Barents Sea. Graphical abstract: Highlights: Riverine discharge dominates freshwater budget in the White Sea. Sea ice formation does not contribute to deep waters in the White Sea basin. High terrestrial DOM signal in the White Sea contrasts marine DOM from Barents Sea. Strong linear relationship found between CDOM absorption and DOC. Terrestrial DOM signal is exported unaltered to the Barents Sea and Arctic shelf.