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Climate of the Past An interactive open-access journal of the European Geosciences Union
doi:10.5194/cp-2015-167
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
14 Mar 2016
Review status
This discussion paper has been under review for the journal Climate of the Past (CP). A final paper in CP is not foreseen.
Circulation and oxygenation of the glacial South China Sea
Shuh-Ji Kao1, Tzu-Ling Chiang2, Da-Wei Li1, Yi-Chia Hsin3, Li-Wei Zheng1, Jin-Yu Terence Yang1, Shih-Chieh Hsu3, Chau-Ron Wu2, and Minhan Dai1 1State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361102, China
2Department of Earth Sciences, National Taiwan Normal University, Taipei, Taiwan
3Research Center for Environmental Changes, Academia Sinica, Taipei, Taiwan
Abstract. Degree of oxygenation in intermediate water modulates the downward transferring efficiency of primary productivity (PP) from surface water to deep water for carbon sequestration, consequently, the storage of nutrients versus the delivery and sedimentary burial fluxes of organic matter and associated biomarkers. To better decipher the PP history of the South China Sea (SCS), appreciation about the glacial-interglacial variation of the Luzon Strait (LS) throughflow, which determines the mean residence time and oxygenation of water mass in the SCS interior, is required. Based on a well-established physical model, we conducted a 3-D modeling exercise to quantify the effects of sea level drop and monsoon wind intensity on glacial circulation pattern, thus, to evaluate effects of productivity and circulation-induced oxygenation on the burial of organic matter. Under modern climatology wind conditions, a 135 m sea level drop results in a greater basin closeness and a ~ 23 % of reduction in the LS intermediate westward throughflow, consequently, an increase in the mean water residence time (from 19 to 23 year). However, when the wind intensity was doubled during glacial low, the throughflow restored largely to reach a similar residence time (18.4 years) as today regardless its closeness. Comparing with present day SCS, surface circulation pattern in glacial model exhibits (1) stronger upwellings at the west off Luzon Island and the east off Vietnam, and (2) an intensified southwestward jet current along the western boundary of the SCS basin. Superimposed hypothetically by stronger monsoon wind, the glacial SCS conditions facilitate greater primary productivity. Manganese, a redox sensitive indicator, in IMAGES core MD972142 at southeastern SCS revealed a relatively reducing environment in glacial periods. Considering the similarity in the mean water residence time between modern and glacial cases, the reducing environment of the glacial southeastern SCS was thus ascribed to a productivity-induced rather than ventilation-induced consequence.

Citation: Kao, S.-J., Chiang, T.-L., Li, D.-W., Hsin, Y.-C., Zheng, L.-W., Yang, J.-Y. T., Hsu, S.-C., Wu, C.-R., and Dai, M.: Circulation and oxygenation of the glacial South China Sea, Clim. Past Discuss., doi:10.5194/cp-2015-167, 2016.
Shuh-Ji Kao et al.
Interactive discussionStatus: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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RC1: 'Review of Kao et al.', Anonymous Referee #1, 26 Apr 2016 Printer-friendly Version 
AC1: 'Reply to Anonymous Referee#1', Shuh-Ji Kao, 15 Jun 2016 Printer-friendly Version Supplement 
 
RC2: 'Review comments', Anonymous Referee #2, 19 May 2016 Printer-friendly Version 
 
AC2: 'Reply to Anonymous Referee#2', Shuh-Ji Kao, 15 Jun 2016 Printer-friendly Version Supplement 
Shuh-Ji Kao et al.
Shuh-Ji Kao et al.

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Short summary
A 3-D model was run for the South China Sea to explore the effects of sea level drop and monsoon wind intensity on glacial patterns of circulation and ventilation. Winter northeasterly monsoon wind intensity governs the volume transport of Kuroshio intrusion through the Luzon Strait, subsequently, the water exchange rate and the mean residence time of water body of the SCS.
A 3-D model was run for the South China Sea to explore the effects of sea level drop and monsoon...
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