Preprints
https://doi.org/10.5194/bg-2021-48
https://doi.org/10.5194/bg-2021-48

  25 Feb 2021

25 Feb 2021

Review status: a revised version of this preprint was accepted for the journal BG and is expected to appear here in due course.

A modeling study of temporal and spatial pCO2 variability on the biologically active and temperature-dominated Scotian Shelf

Krysten Rutherford1, Katja Fennel1, Dariia Atamanchuk1, Douglas Wallace1, and Helmuth Thomas1,2 Krysten Rutherford et al.
  • 1Department of Oceanography, Dalhousie University, 1355 Oxford Street, Halifax, Nova Scotia, B3H 4R2, Canada
  • 2Institute of Coastal Research, Helmholtz Center Geesthacht, D-215502 Geesthacht, Germany

Abstract. Continental shelves are thought to be affected disproportionately by climate change and are a large contributor to global air-sea carbon dioxide (CO2) fluxes. It is often reported that low-latitude shelves tend to act as net sources of CO2 whereas mid- and high-latitude shelves act as net sinks. Here, we combine a high-resolution regional model with surface water time-series and repeat transect observations from the Scotian Shelf, a mid-latitude region in the northwest North Atlantic, to determine what processes are driving the temporal and spatial variability of partial pressure of CO2 (pCO2). In contrast to the global trend, the Scotian Shelf acts as a net source. Surface pCO2 undergoes a strong seasonal cycle associated with both a strong biological drawdown of Dissolved Inorganic Carbon (DIC) in spring, and pronounced effects of temperature, which ranges from 0 °C in the winter to near 20 °C in the summer. Throughout the summer, events with low surface-water pCO2 occur nearshore associated with coastal upwelling. This effect of upwelling on pCO2 is also in contrast to the general assumption that upwelling increases surface pCO2 by delivering DIC-enriched water to the surface. Aside from these localized events, pCO2 is relatively uniform across the shelf. Our model agrees with regional observations, reproduces seasonal patterns of pCO2, and simulates annual outgassing of CO2 from the ocean of +1.9 ± 0.2 mol C m−2 yr−1 for the Scotian Shelf, net neutral CO2 flux of −0.09 ± 0.16 mol C m−2 yr−1 for the Gulf of Maine and uptake by the ocean of −0.88 ± 0.4 mol C m−2 yr−1 for the Grand Banks.

Krysten Rutherford et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2021-48', Anonymous Referee #1, 28 Mar 2021
  • RC2: 'Comment on bg-2021-48', Claudine Hauri, 27 Apr 2021

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2021-48', Anonymous Referee #1, 28 Mar 2021
  • RC2: 'Comment on bg-2021-48', Claudine Hauri, 27 Apr 2021

Krysten Rutherford et al.

Krysten Rutherford et al.

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Short summary
Using a regional model of the northwestern North Atlantic shelves in combination with a surface water time series and repeat transect observations, we investigate surface CO2 variability on the Scotian Shelf. The study highlights a strong seasonal cycle in shelf-wide pCO2 and spatial variability throughout the summer months driven by physical events. The simulated net flux of CO2 on the Scotian Shelf is out of the ocean, deviating from the global air-sea CO2 flux trend in continental shelves.
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