A modeling study of temporal and spatial pCO2 variability on the biologically active and temperature-dominated Scotian Shelf
Continental shelves are thought to be affected disproportionately by climate change and are a large contributor to global air-sea carbon dioxide (CO 2 ) fluxes. It is often reported that low-latitude shelves tend to act as net sources of CO 2 whereas mid- and high-latitude shelves act as net sinks....
| Main Authors: | , , , , |
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| Format: | Text |
| Language: | English |
| Published: |
2021
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| Subjects: | |
| Online Access: | https://doi.org/10.5194/bg-2021-48 https://bg.copernicus.org/preprints/bg-2021-48/ |
| Summary: | Continental shelves are thought to be affected disproportionately by climate change and are a large contributor to global air-sea carbon dioxide (CO 2 ) fluxes. It is often reported that low-latitude shelves tend to act as net sources of CO 2 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 CO 2 ( p CO 2 ). In contrast to the global trend, the Scotian Shelf acts as a net source. Surface p CO 2 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 p CO 2 occur nearshore associated with coastal upwelling. This effect of upwelling on p CO 2 is also in contrast to the general assumption that upwelling increases surface p CO 2 by delivering DIC-enriched water to the surface. Aside from these localized events, p CO 2 is relatively uniform across the shelf. Our model agrees with regional observations, reproduces seasonal patterns of p CO 2 , and simulates annual outgassing of CO 2 from the ocean of +1.9 ± 0.2 mol C m −2 yr −1 for the Scotian Shelf, net neutral CO 2 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. |
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