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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2019-16
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-16
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 23 Jan 2019

Submitted as: research article | 23 Jan 2019

Review status
This discussion paper is a preprint. It has been under review for the journal Biogeosciences (BG). The revised manuscript was not accepted.

Drivers of 21st Century carbon cycle variability in the North Atlantic Ocean

Matthew P. Couldrey1,a, Kevin I. C. Oliver1, Andrew Yool2, Paul R. Halloran3, and Eric P. Achterberg1,4 Matthew P. Couldrey et al.
  • 1Ocean and Earth Science, University of Southampton, National Oceanography Centre, Southampton, UK
  • 2National Oceanography Centre, Southampton, UK
  • 3Geography, College of Life and Environmental Sciences, University of Exeter, UK
  • 4GEOMAR Helmholtz-Zentrum für Ozeanforschung, Kiel, Germany
  • anow at: Department of Meteorology, University of Reading, Reading, UK

Abstract. The North Atlantic carbon sink is a prominent component of global climate, storing large amounts of atmospheric carbon dioxide (CO2), but this basin’s CO2 uptake variability presents challenges for future climate prediction. A comprehensive mechanistic understanding of the processes that give rise to year-to-year (interannual) and decade-to-decade (decadal) variability in the North Atlantic’s dissolved inorganic carbon (DIC) inventory is lacking. Here, we numerically simulate the oceanic response to human-induced (anthropogenic) climate change from the industrial era to the year 2100. The model distinguishes how different physical, chemical, and biological processes modify the basin’s DIC inventory; the saturation, soft tissue, and carbonate pumps, anthropogenic emissions, and other processes causing air-sea disequilibria. There are four ‘natural’ pools (saturation, soft tissue, carbonate, and disequilibrium), and an ‘anthropogenic’ pool. Interannual variability of the North Atlantic DIC inventory arises primarily due to temperature- and alkalinity-induced changes in carbon solubility (saturation concentrations). A mixture of saturation and anthropogenic drivers cause decadal variability. Multidecadal variability results from the opposing effects of saturation versus soft tissue carbon, and anthropogenic carbon uptake. By the year 2100, the North Atlantic gains 66 Pg (1 Pg = 1015 grams) of anthropogenic carbon, and the natural carbon pools collectively decline by 4.8 Pg. The first order controls on interannual variability of the North Atlantic carbon sink size are therefore largely physical, and the biological pump emerges as an important driver of change on multidecadal timescales. Further work should identify specifically which physical processes underlie the interannual saturation-dominated DIC variability documented here.

Matthew P. Couldrey et al.
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Interactive discussion
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Matthew P. Couldrey et al.
Matthew P. Couldrey et al.
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Short summary
Determining how much carbon dioxide (CO2) the oceans absorb is key to predicting human-caused climate change. A computer model of the ocean shows how the North Atlantic will change up to the end of the century. Year-to-year variations are mostly caused by changes in ocean temperature and seawater chemistry, altering CO2 solubility. By 2100, human emissions cause the biggest changes. The near term changes are physically driven, which may be more predictable than biological changes.
Determining how much carbon dioxide (CO2) the oceans absorb is key to predicting human-caused...
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