Pore fluid compositions and inferred fluid flow patterns at the Haima cold seeps of the South China Sea

Polygonal faults were identified from three-dimensional (3D) seismic data in the middle-late Miocene marine sequences of the South China Sea. Polygonal faults in the study area are normal faults with fault lengths ranging from 100 to 1500 m, fault spaces ranging from 40 to 800 m, and throws ranging from 10 to 40 m. Gas hydrate was inferred from the seismic polarity, the reflection strength, and the temperature-pressure equilibrium computation results. Gas hydrates located in the sediments above the polygonal faults layer. Polygonal faults can act as pathways for the migration of fluid flow, which can supply hydrocarbons for the formation of gas hydrates.

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KONDISI OSEANOGRAFI DI SELAT MATAK KABUPATEN KEPULAUAN ANAMBAS MELALUI MODEL HIDRODINAMIKA

Jurnal Air Indonesia ◽

10.29122/jai.v7i2.2416 ◽

2018 ◽

Vol 7 (2) ◽

Author(s):

Agung Riyadi ◽

Nusa Idaman Said ◽

Matih Santos

Keyword(s):

South China Sea ◽

Flow Velocity ◽

South China ◽

High Tide ◽

Maximum Flow ◽

Flow Patterns ◽

The South China Sea ◽

The South ◽

The West ◽

China Sea

This paper describes some of the general condition of the oceanographic parameters in the Strait Matak, Anambas Archipelago. The data flow is obtained by direct measurement by using a current meter types RCM-7. Simulation models using Mike 21. Mike flow pattern is divided into two seasons, namely west season (January) and the east season (August) and flow patterns ahead of the tide when the season is generally moving west to wards the south, it demonstrates the role of strong tidal influence the movement of waterin the study area. Flow velocity in the strait just before the tide on the west season reaches 1m/s. Flow patterns at high tide on the west season looks still moving toward sthe south. The maximum flow velocity in the strait when the tide reaches 0.32 m/s, while the average speed in the area of the model is 0.12 m/s. Low tide towards the current pattern is still moving towards the south, it reinforces the notion that in addition to tidal windsare also very significant role in moving the flow, in this case that the current is moving toward the south. Flow velocity just before low tide reaches 0.85 m/s. Flow patterns at low tide shows the differences in the three previous conditions, the current in the strait to move out to the north toward the South China Sea. In condition slow tide, the tida lmore dominantly than the wind, this proved to even though the wind toward the south, the currents inthestraitis moving toward snorth along the tidal flow leading to the South China Sea. Flow velocity is quite varied location of modeling; flow velocity at low tide reaches 0.5m/s, with the average 0.15 m/s. Keywords: current and direction, wind, tide, model.

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Methane Source and Turnover in the Shallow Sediments to the West of Haima Cold Seeps on the Northwestern Slope of the South China Sea

Geofluids ◽

10.1155/2019/1010824 ◽

2019 ◽

Vol 2019 ◽

pp. 1-18 ◽

Cited By ~ 3

Author(s):

Junxi Feng ◽

Shengxiong Yang ◽

Hongbin Wang ◽

Jinqiang Liang ◽

Yunxin Fang ◽

...

Keyword(s):

Steady State ◽

South China Sea ◽

South China ◽

Methane Flux ◽

The South China Sea ◽

Cold Seeps ◽

The South ◽

The West ◽

China Sea ◽

Methane Fluxes

The Haima cold seeps are active cold seep areas that were recently discovered on the northwestern slope of the South China Sea (SCS). Three piston cores (CL30, CL44, and CL47) were collected within an area characterized by bottom simulating reflectors to the west of Haima cold seeps. Porewater profiles of the three cores exhibit typical kink-type feature, which is attributed to elevated methane flux (CL30) and bubble irrigation (CL44 and CL47). By simulating the porewater profiles of SO42-, CH4, PO43-, Ca2+, Mg2+, and dissolved inorganic carbon (DIC) in CL44 and CL47 using a steady-state reaction-transport model, we estimated that the dissolved SO42- was predominantly consumed by anaerobic oxidation of methane (AOM) at rates of 74.3 mmol m−2 yr−1 in CL44 and 85.0 mmol m−2 yr−1 in CL47. The relatively high AOM rates were sustained by free gas dissolution rather than local methanogenesis. Based on the diffusive Ba2+ fluxes and the excess barium contents in the sediments slightly above the current SMTZ, we estimated that methane fluxes at core CL44 and CL47 have persisted for ca. 3 kyr and 0.8-1.6 kyr, respectively. The non-steady-state modeling for CL30 predicted that a recent increase in upward dissolved methane flux was initiated ca. 85 yr ago. However, the required time for the formation of the barium front above the SMTZ at this core is much longer (ca. 2.2-4.2 kyr), which suggests that the depth of SMTZ possibly has fluctuated due to episodic changes in methane flux. Furthermore, using the model-derived fractions of different DIC sources and the δ13CDIC mass balance calculation, we estimated that the δ13C values of the external methane in cores CL30, CL44, and CL47 are -74.1‰, -75.4‰, and -66.7‰, respectively, indicating the microbial origin of methane. Our results suggest that methane seepage in the broader area surrounding the Haima cold seeps probably has persisted at least hundreds to thousands of years with changing methane fluxes.

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Corrigendum to “Vertical shifts of particle-attached and free-living prokaryotes in the water column above the cold seeps of the South China Sea” [Mar. Pollut. Bull. Volume 156, July 2020, 111,230]

Marine Pollution Bulletin ◽

10.1016/j.marpolbul.2020.111472 ◽

2020 ◽

Vol 158 ◽

pp. 111472

Author(s):

Yue Zhang ◽

Hongmei Jing ◽

Xiaotong Peng

Keyword(s):

South China Sea ◽

Water Column ◽

South China ◽

The South China Sea ◽

Cold Seeps ◽

The South ◽

Free Living ◽

China Sea

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Synoptic Flow Patterns and Large-Scale Characteristics Associated with Rapidly Intensifying Tropical Cyclones in the South China Sea

Monthly Weather Review ◽

10.1175/mwr-d-13-00338.1 ◽

2015 ◽

Vol 143 (1) ◽

pp. 64-87 ◽

Cited By ~ 23

Author(s):

Xiaomin Chen ◽

Yuqing Wang ◽

Kun Zhao

Keyword(s):

Environmental Factors ◽

South China Sea ◽

Tropical Cyclones ◽

South China ◽

Surface Wind ◽

Flow Patterns ◽

The South China Sea ◽

Intensity Change ◽

The South ◽

China Sea

Abstract The typical synoptic flow patterns and environmental factors that favor the rapid intensification (RI) of tropical cyclones (TCs) in the South China Sea (SCS) have been identified based on all TCs formed in the SCS between 1981 and 2011. The quantity RI is defined as the 24-h increase in maximum sustained surface wind speed by 15 m s−1 as in previous studies, which is close to the 95th percentile of 24-h intensity change of all SCS samples excluding those after landfall. There are 4.9% (2.3%) of tropical depressions (tropical storms) that experienced RI. No typhoons satisfied the RI threshold. Six low-level synoptic flow patterns favoring RI have been identified based on 18 RI cases. In the monsoon season very few TCs experience RI due to large vertical wind shear (VWS). Most RI cases occurred in the postmonsoon season when the midlatitude troughs often penetrated into the SCS whereas the southwesterly monsoon flow is still strong in the southern SCS. Compared with those of non-RI cases, the mean initial conditions of RI cases include weak VWS and relatively strong forcing from midlatitude troughs. Several criteria of significant environmental factors for RI are statistically identified based on all TC samples. It is found that 16 non-RI TCs fitted in the RI flow patterns but only two of them satisfy all the criteria, suggesting that a combination of the synoptic flow pattern and the environmental factors can be used to predict RI in the SCS. In addition, two RI cases involving TC–trough interaction are analyzed.

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