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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 13, issue 22
Biogeosciences, 13, 6155–6169, 2016
https://doi.org/10.5194/bg-13-6155-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 13, 6155–6169, 2016
https://doi.org/10.5194/bg-13-6155-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 22 Nov 2016

Research article | 22 Nov 2016

Seasonal variation of CaCO3 saturation state in bottom water of a biological hotspot in the Chukchi Sea, Arctic Ocean

Michiyo Yamamoto-Kawai1, Takahisa Mifune1, Takashi Kikuchi2, and Shigeto Nishino2 Michiyo Yamamoto-Kawai et al.
  • 1Tokyo University of Marine Science and Technology, Tokyo, 108-8477, Japan
  • 2Japan Agency for Marine-Earth Science and Technology, Yokosuka, 237-0061, Japan

Abstract. Distribution of calcium carbonate saturation state (Ω) was observed in the Chukchi Sea in autumn 2012 and early summer 2013. Ω in bottom water ranged from 0.3 to 2.0 for aragonite and from 0.5 to 3.2 for calcite in 2012. In 2013, Ω in bottom water was 1.1–2.8 for aragonite and 1.7–4.4 for calcite. Aragonite and calcite undersaturation was found in high productivity regions in autumn 2012 but not in early summer 2013. Comparison with other parameters has indicated that biological processes – respiration and photosynthesis – are major factors controlling the regional and temporal variability of Ω. From these ship-based observations, we have obtained empirical equations to reconstruct Ω from temperature, salinity and apparent oxygen utilization. Using 2-year-round mooring data and these equations, we have reconstructed seasonal variation of Ω in bottom water in Hope Valley, a biological hotspot in the southern Chukchi Sea. Estimated Ω was high in spring and early summer, decreased in later summer, and remained relatively low in winter. Calculations indicated a possibility that bottom water could have been undersaturated for aragonite on an intermittent basis even in the pre-industrial period, and that anthropogenic CO2 has extended the period of aragonite undersaturation to more than 2-fold longer by now.

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Seasonal variation of Ω in bottom water in Hope Valley, a biological hotspot in the southern Chukchi Sea, was reconstructed from 2-year-round mooring data of temperature, salinity and oxygen, with empirical equations derived from ship-based observations.
Seasonal variation of Ω in bottom water in Hope Valley, a biological hotspot in the southern...
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