AUTHOR=Chierici Melissa , Vernet Maria , Fransson Agneta , Børsheim Knut Yngve TITLE=Net Community Production and Carbon Exchange From Winter to Summer in the Atlantic Water Inflow to the Arctic Ocean JOURNAL=Frontiers in Marine Science VOLUME=6 YEAR=2019 URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2019.00528 DOI=10.3389/fmars.2019.00528 ISSN=2296-7745 ABSTRACT=

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.