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Net community production and carbon exchange from winter to summer in the Atlantic Water inflow to the Arctic Ocean

TitleNet community production and carbon exchange from winter to summer in the Atlantic Water inflow to the Arctic Ocean
Publication TypeJournal Article
Year of Publication2019
AuthorsChierici M., Vernet M, Fransson A., Borsheim K.Y
Date Published2019/09
Type of ArticleArticle
Accession NumberWOS:000485004900001
Keywordsamundsen; Atlantic water; Denitrification; Environmental Sciences & Ecology; export; fram strait; Fram Strait and Svalbard shelf; gulf; impact; marginal ice-zone; Marine & Freshwater Biology; nitrogen-fixation; north; ocean acidification; ocean CO2 sink; primary production; recirculation; sea ice melt water; sea-ice; variability

The eastern Fram Strait and area north of Svalbard, are influenced by the inflow of warm Atlantic water, which is high in nutrients and CO2, influencing the carbon flux into the Arctic Ocean. However, these estimates are mainly based on summer data and there is still doubt on the size of the net ocean Arctic CO2 sink. We use data on carbonate chemistry and nutrients from three cruises in 2014 in the CarbonBridge project (January, May, and August) and one in Fram Strait (August). We describe the seasonal variability and the major drivers explaining the inorganic carbon change (C-DIC) in the upper 50 m, such as photosynthesis (C-BIO), and air-sea CO2 exchange (C-EXCH). Remotely sensed data describes the evolution of the bloom and net community production. The focus area encompasses the meltwater-influenced domain (MWD) along the ice edge, the Atlantic water inflow (AWD), and the West Spitsbergen shelf (SD). The C-BIO total was 2.2 mol C m(-2) in the MWD derived from the nitrate consumption between January and May. Between January and August, the C-BIO was 3.0 mol C m(-2) in the AWD, thus C-BIO between May and August was 0.8 mol C m(-2). The ocean in our study area mainly acted as a CO2 sink throughout the period. The mean CO2 sink varied between 0.1 and 2.1 mol C m(-2) in the AWD in August. By the end of August, the AWD acted as a CO2 source of 0.7 mol C m(-2), attributed to vertical mixing of CO2-rich waters and contribution from respiratory CO2 as net community production declined. The oceanic CO2 uptake (C-EXCH) from the atmosphere had an impact on C-DIC between 5 and 36%, which is of similar magnitude as the impact of the calcium carbonate (CaCO3, C-CALC) dissolution of 6-18%. C-CALC was attributed to be caused by a combination of the sea-ice ikaite dissolution and dissolution of advected CaCO3 shells from the south. Indications of denitrification were observed, associated with sea-ice meltwater and bottom shelf processes. C-BIO played a major role (48-89%) for the impact on C-DIC.

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