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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 12, issue 23
Biogeosciences, 12, 6881-6896, 2015
https://doi.org/10.5194/bg-12-6881-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 12, 6881-6896, 2015
https://doi.org/10.5194/bg-12-6881-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 02 Dec 2015

Research article | 02 Dec 2015

Carbonate saturation state of surface waters in the Ross Sea and Southern Ocean: controls and implications for the onset of aragonite undersaturation

H. B. DeJong, R. B. Dunbar, D. Mucciarone, and D. A. Koweek H. B. DeJong et al.
  • Department of Earth System Science, Stanford University, Stanford, CA, USA

Abstract. Predicting when surface waters of the Ross Sea and Southern Ocean will become undersaturated with respect to biogenic carbonate minerals is challenging in part due to the lack of baseline high-resolution carbon system data. Here we present ~ 1700 surface total alkalinity measurements from the Ross Sea and along a transect between the Ross Sea and southern Chile from the austral autumn (February–March 2013). We calculate the saturation state of aragonite (ΩAr) and calcite (Ω Ca) using measured total alkalinity and pCO2. In the Ross Sea and south of the Polar Front, variability in carbonate saturation state (Ω) is mainly driven by algal photosynthesis. Freshwater dilution and calcification have minimal influence on Ω variability. We estimate an early spring surface water ΩAr value of ~ 1.2 for the Ross Sea using a total alkalinity–salinity relationship and historical pCO2 measurements. Our results suggest that the Ross Sea is not likely to become undersaturated with respect to aragonite until the year 2070.

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We calculate the carbonate saturation state of surface water from the Ross Sea and along a transect between the Ross Sea and southern Chile using ~ 1700 total alkalinity measurements. Our results suggest that variability in surface carbonate saturation state is driven by biological productivity. We argue that in the Ross Sea the aragonite saturation state of surface water during the early spring never falls below 1.2.
We calculate the carbonate saturation state of surface water from the Ross Sea and along a...
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