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Biogeosciences An interactive open-access journal of the European Geosciences Union
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© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Reviews and syntheses 20 Sep 2018

Reviews and syntheses | 20 Sep 2018

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Biogeosciences (BG).

Carbon cycling in the North American coastal ocean: A synthesis

Katja Fennel1, Simone Alin2, Leticia Barbero3, Wiley Evans4, Timotheé Bourgeois1, Sarah Cooley5, John Dunne6, Richard A. Feely2, Jose Martin Hernandez-Ayon7, Xinping Hu8, Steven Lohrenz9, Frank Muller-Karger10, Raymond Najjar11, Lisa Robbins10, Elizabeth Shadwick12, Samantha Siedlecki13, Nadja Steiner14, Adrienne Sutton2, Daniela Turk1, Penny Vlahos13, and Zhaohui Aleck Wang15 Katja Fennel et al.
  • 1Department of Oceanography, Dalhousie University, 1355 Oxford Street, Halifax B3H 4R2, Nova Scotia, Canada
  • 2NOAA Pacific Marine Environmental Laboratory
  • 3NOAA Atlantic Oceanographic and Meteorological Laboratory
  • 4Hakai Institute
  • 5Ocean Conservancy
  • 6NOAA Geophysical Fluid Dynamics Laboratory
  • 7Autonomous University of Baja California
  • 8Texas A&M University, Corpus Christi
  • 9University of Massachusetts, Dartmouth
  • 10University of South Florida
  • 11Pennsylvania State University
  • 12Virginia Institute of Marine Science
  • 13University of Connecticut
  • 14Department of Fisheries and Oceans Canada
  • 15Woods Hole Oceanographic Institution

Abstract. A quantification of carbon fluxes in the coastal ocean and across its boundaries, specifically the air-sea, land-to-coastal-ocean and coastal-to-open-ocean interfaces, is important for assessing the current state and projecting future trends in ocean carbon uptake and coastal ocean acidification, but is currently a missing component of global carbon budgeting. This synthesis reviews recent progress in characterizing these carbon fluxes with focus on the North American coastal ocean. Several observing networks and high-resolution regional models are now available. Recent efforts have focused primarily on quantifying net air-sea exchange of carbon dioxide (CO2). Some studies have estimated other key fluxes, such as the exchange of organic and inorganic carbon between shelves and the open ocean. Available estimates of air-sea CO2 flux, informed by more than a decade of observations, indicate that the North American margins act as a net sink for atmospheric CO2. This net uptake is driven primarily by the high-latitude regions. The estimated magnitude of the net flux is 160 ± 80 Tg C/y for the North American Exclusive Economic Zone, a number that is not well constrained. The increasing concentration of inorganic carbon in coastal and open-ocean waters leads to ocean acidification. As a result conditions favouring dissolution of calcium carbonate occur regularly in subsurface coastal waters in the Arctic, which are naturally prone to low pH, and the North Pacific, where upwelling of deep, carbon-rich waters has intensified and, in combination with the uptake of anthropogenic carbon, leads to low seawater pH and aragonite saturation states during the upwelling season. Expanded monitoring and extension of existing model capabilities are required to provide more reliable coastal carbon budgets, projections of future states of the coastal ocean, and quantification of anthropogenic carbon contributions.

Katja Fennel et al.
Interactive discussion
Status: final response (author comments only)
Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Katja Fennel et al.
Katja Fennel et al.
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Short summary
We review and synthesize available information on coastal ocean carbon fluxes around North America (NA). There is overwhelming evidence, compiled and discussed here, that the NA coastal margins act as a sink. Our synthesis shows the great diversity in processes driving carbon fluxes in different coastal regions, highlights remaining gaps in observations and models, and discusses current and anticipated future trends with respect to carbon fluxes and acidification.
We review and synthesize available information on coastal ocean carbon fluxes around North...