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The seasonal cycle of carbonate system processes in Ryder Bay, West Antarctic Peninsula

The seasonal cycle of carbonate system processes in Ryder Bay, West Antarctic Peninsula
The seasonal cycle of carbonate system processes in Ryder Bay, West Antarctic Peninsula
The carbon cycle in seasonally sea-ice covered waters remains poorly understood due to both a lack of observational data and the complexity of the system. Here we present three consecutive seasonal cycles of upper ocean dissolved inorganic carbon (DIC) and total alkalinity measurements from Ryder Bay on the West Antarctic Peninsula. We attribute the observed changes in DIC to four processes: mixing of water masses, air–sea CO2 flux, calcium carbonate precipitation/dissolution and photosynthesis/respiration. This approach enables us to resolve the main drivers of the seasonal DIC cycle and also investigate the mechanisms behind interannual variability in the carbonate system. We observe a strong, asymmetric seasonal cycle in the carbonate system, driven by physical processes and primary production. In summer, melting glacial ice and sea ice and a reduction in mixing with deeper water reduce the concentration of DIC in surface waters. The dominant process affecting the carbonate system is net photosynthesis which reduces DIC and the fugacity of CO2, making the ocean a net sink of atmospheric CO2. In winter, mixing with deeper, carbon-rich water and net heterotrophy increase surface DIC concentrations, resulting in pH as low as 7.95 and aragonite saturation states close to 1. We observe no clear seasonal cycle of calcium carbonate precipitation/dissolution but some short-lived features of the carbonate time series strongly suggest that significant precipitation of calcium carbonate does occur in the Bay. The variability observed in this study demonstrates that changes in mixing and sea-ice cover significantly affect carbon cycling in this dynamic environment. Maintaining this unique time series will allow the carbonate system in seasonally sea-ice covered waters to be better understood.
0967-0645
167–180
Legge, Oliver J.
bbf39255-199a-4fc6-86e1-2db3c4c7feb9
Bakker, Dorothee C.e.
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Meredith, Michael P.
25fd5f1c-f3ed-40a2-af59-5a7074a25fcd
Venables, Hugh J.
57810ecf-cff4-4b43-ba17-84cdbaca4e9a
Brown, Peter J.
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Jones, Elizabeth M.
cb5969b2-d139-4c67-acae-5e9405adf3a6
Johnson, Martin T.
4f5f46ef-4ee9-4399-88e2-982aed83a7ed
Legge, Oliver J.
bbf39255-199a-4fc6-86e1-2db3c4c7feb9
Bakker, Dorothee C.e.
45bd5b18-a7c0-4343-9972-c2e451bf773e
Meredith, Michael P.
25fd5f1c-f3ed-40a2-af59-5a7074a25fcd
Venables, Hugh J.
57810ecf-cff4-4b43-ba17-84cdbaca4e9a
Brown, Peter J.
8b4b4591-6932-4d1a-b528-4a8370d7dad9
Jones, Elizabeth M.
cb5969b2-d139-4c67-acae-5e9405adf3a6
Johnson, Martin T.
4f5f46ef-4ee9-4399-88e2-982aed83a7ed

Legge, Oliver J., Bakker, Dorothee C.e., Meredith, Michael P., Venables, Hugh J., Brown, Peter J., Jones, Elizabeth M. and Johnson, Martin T. (2017) The seasonal cycle of carbonate system processes in Ryder Bay, West Antarctic Peninsula. Deep Sea Research Part II: Topical Studies in Oceanography, 139, 167–180. (doi:10.1016/j.dsr2.2016.11.006).

Record type: Article

Abstract

The carbon cycle in seasonally sea-ice covered waters remains poorly understood due to both a lack of observational data and the complexity of the system. Here we present three consecutive seasonal cycles of upper ocean dissolved inorganic carbon (DIC) and total alkalinity measurements from Ryder Bay on the West Antarctic Peninsula. We attribute the observed changes in DIC to four processes: mixing of water masses, air–sea CO2 flux, calcium carbonate precipitation/dissolution and photosynthesis/respiration. This approach enables us to resolve the main drivers of the seasonal DIC cycle and also investigate the mechanisms behind interannual variability in the carbonate system. We observe a strong, asymmetric seasonal cycle in the carbonate system, driven by physical processes and primary production. In summer, melting glacial ice and sea ice and a reduction in mixing with deeper water reduce the concentration of DIC in surface waters. The dominant process affecting the carbonate system is net photosynthesis which reduces DIC and the fugacity of CO2, making the ocean a net sink of atmospheric CO2. In winter, mixing with deeper, carbon-rich water and net heterotrophy increase surface DIC concentrations, resulting in pH as low as 7.95 and aragonite saturation states close to 1. We observe no clear seasonal cycle of calcium carbonate precipitation/dissolution but some short-lived features of the carbonate time series strongly suggest that significant precipitation of calcium carbonate does occur in the Bay. The variability observed in this study demonstrates that changes in mixing and sea-ice cover significantly affect carbon cycling in this dynamic environment. Maintaining this unique time series will allow the carbonate system in seasonally sea-ice covered waters to be better understood.

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Accepted/In Press date: 15 November 2016
Published date: 1 May 2017
Organisations: National Oceanography Centre, Marine Physics and Ocean Climate

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Local EPrints ID: 406820
URI: http://eprints.soton.ac.uk/id/eprint/406820
ISSN: 0967-0645
PURE UUID: 839e56b4-2f24-4e32-be3f-eeb51bf43eed

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Date deposited: 23 Mar 2017 02:03
Last modified: 15 Mar 2024 12:53

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Contributors

Author: Oliver J. Legge
Author: Dorothee C.e. Bakker
Author: Michael P. Meredith
Author: Hugh J. Venables
Author: Peter J. Brown
Author: Elizabeth M. Jones
Author: Martin T. Johnson

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