Provenance and weathering of sediments in the deep basin of the northern South China Sea during the last 38 kyr

AbstractBoth internal solitary waves (ISWs) and mesoscale eddies are ubiquitous in the northern South China Sea (SCS). In this study, the authors examine the impacts of mesoscale eddies on the ISWs transiting the northern SCS deep basin that evolve from the steepening internal tide generated in the Luzon Strait, using in situ data collected from a specifically designed mooring array. From November 2013 to January 2014, an energetic mesoscale eddy pair consisting of one anticyclonic eddy (AE) and one cyclonic eddy (CE) propagated across the mooring array. Observations revealed that the amplitude, propagation direction, and speed of the transbasin ISWs were significantly modulated by the eddy pair. When the moorings were covered by the southern portion of the AE, the ISW amplitudes decreased by as much as 67% because of the thermocline deepening along the wave direction and the energy divergence along the wave front. When the moorings were covered by the northern portions of both eddies, the amplitude of ISWs also decreased but to a relatively smaller degree. ISWs propagated the fastest inside the southern portion of the AE, where both the thermocline deepening and eddy currents enhanced the propagation speed of ISWs. Under the influence of the AE (CE) core, ISWs propagated more northward (southward) than usual. The observational results reported here highlight the importance of resolving mesoscale eddies in circulation–internal wave coupled models to accurately predict kinematic characteristics of ISWs.

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Coupling of surface pCO2 and dissolved oxygen in the northern South China Sea: impacts of contrasting coastal processes

Biogeosciences Discussions ◽

10.5194/bgd-6-6249-2009 ◽

2009 ◽

Vol 6 (3) ◽

pp. 6249-6269 ◽

Cited By ~ 2

Author(s):

W. Zhai ◽

M. Dai ◽

W. Cai

Keyword(s):

South China Sea ◽

Dissolved Oxygen ◽

South China ◽

Coastal Upwelling ◽

Northern South China Sea ◽

River Estuary ◽

Pearl River Estuary ◽

Deep Basin ◽

Co2 Partial Pressure ◽

China Sea

Abstract. We examined the relationship between CO2 partial pressure (pCO2) and dissolved oxygen (DO) based on a cruise conducted in July 2004 to the northern South China Sea, spanning from estuarine plume, coastal upwelling and deep basin areas. Distinct relationships between pCO2 and DO saturation were identified in different regimes. In coastal upwelling areas and the Pearl River estuary, biological drawdown of pCO2 and production of O2 were simultaneously observed. The two properties were coupled with each other primarily via photosynthesis and respiration. The stoichiometric relationship of the two properties however, was quite different in these two environments due to different values of the Revelle factor. In the offshore areas, apart from the estuary and upwelling, the dynamics of pCO2 and DO were mainly influenced by air-sea exchange during water mixing. Given the fact that air-sea re-equilibration of O2 is much faster than that of CO2, the observed pCO2-DO relationship deviated from that of the theoretical prediction based on the Redfield relationship in the offshore areas.

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Coupling of surface pCO2 and dissolved oxygen in the northern South China Sea: impacts of contrasting coastal processes

Biogeosciences ◽

10.5194/bg-6-2589-2009 ◽

2009 ◽

Vol 6 (11) ◽

pp. 2589-2598 ◽

Cited By ~ 31

Author(s):

W. D. Zhai ◽

M. Dai ◽

W.-J. Cai

Keyword(s):

South China Sea ◽

Dissolved Oxygen ◽

South China ◽

Coastal Upwelling ◽

Simple Procedure ◽

Northern South China Sea ◽

River Estuary ◽

Deep Basin ◽

China Sea ◽

Spatial Coverage

Abstract. We examined the relationship between CO2 partial pressure (pCO2) and dissolved oxygen (DO) based on a cruise conducted in July 2004 to the northern South China Sea (111°–118° E 18°–23° N), spanning from estuarine plume, coastal upwelling and deep basin areas. Distinct relationships between pCO2 and DO saturation were identified in different regimes. In coastal upwelling areas and the Pearl River estuary, biological drawdown of pCO2 and production of O2 were simultaneously observed. The two properties were coupled with each other primarily via photosynthesis and respiration. The stoichiometric relationship of the two properties however, was quite different in these two environments due to different values of the Revelle factor. In the offshore areas, apart from the estuary and upwelling, the dynamics of pCO2 and DO were mainly influenced by air-sea exchange during water mixing. Given the fact that air-sea re-equilibration of O2 is much faster than that of CO2, the observed pCO2-DO relationship deviated from that of the theoretical prediction based on the Redfield relationship in the offshore areas. Although this study is subject to the limited temporal and spatial coverage of sampling, we have demonstrated a simple procedure to evaluate the community metabolic status based on a combination of high-resolution surface pCO2 and DO measurements, which may have applicability in many coastal systems with a large gradient of changes in their physical and biogeochemical conditions.

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