[1] Physical mechanisms for the summertime offshore detachment of the Changjiang Diluted Water (CDW) into the East China Sea are examined using the high-resolution, unstructured-grid, Finite-Volume Coastal Ocean Model (FVCOM). The model results suggest that isolated low salinity water lens detected west of Cheju Island can be formed by (1) a large-scale adjustment of the flow field to the Changjiang discharge and (2) the detachment of anticyclonic eddies as a result of baroclinic instability of the CDW front. Adding the Changjiang discharge intensifies the clockwise vorticity of the subsurface current (originating from the Taiwan Warm Current) flowing along the 50-m isobath and thus drives the low-salinity water in the northern coastal area of the Changjiang mouth offshore over a submerged plateau that extends toward Cheju Island. Given a model horizontal resolution of less than 1.0 km, the CDW front becomes baroclinically unstable and forms a chain of anticyclonic and cyclonic eddies. The offshore detachment of anticyclonic eddies can carry the CDW offshore. This process is enhanced under northward winds as a result of the spatially nonuniform interaction of wind-induced Ekman flow and eddy-generated frontal density currents. Characteristics of the model-predicted eddy field are consistent with previous theoretical studies of baroclinic instability of buoyancy-driven coastal density currents and existing satellite imagery. The plume stability is controlled by the horizontal Ekman number. In the Changjiang, this number is much smaller than the criterion suggested by a theoretical analysis.
Water flooding plays an important role in recovering oil from depleted petroleum reservoirs. Exactly how the microbial communities of production wells are affected by microorganisms introduced with injected water has previously not been adequately studied. Using denaturing gradient gel electrophoresis (DGGE) approach and 16S rRNA gene clone library analysis, the comparison of microbial communities is carried out between one injection water and two production waters collected from a working block of the water-flooded Gudao petroleum reservoir located in the Yellow River Delta. DGGE fingerprints showed that the similarities of the bacterial communities between the injection water and production waters were lower than between the two production waters. It was also observed that the archaeal composition among these three samples showed no significant difference. Analysis of the 16S rRNA gene clone libraries showed that the dominant groups within the injection water were Betaproteobacteria, Gammaproteobacteria and Methanomicrobia, while the dominant groups in the production waters were Gammaproteobacteria and Methanobacteria. Only 2 out of 54 bacterial operational taxonomic units (OTUs) and 5 out of 17 archaeal OTUs in the injection water were detected in the production waters, indicating that most of the microorganisms introduced by the injection water may not survive to be detected in the production waters. Additionally, there were 55.6% and 82.6% unique OTUs in the two production waters respectively, suggesting that each production well has its specific microbial composition, despite both wells being flooded with the same injection water.
18The occurrence of organophosphate ester (OPE)
A spherical coordinate version of the unstructured grid 3‐D FVCOM (finite volume coastal ocean model) has been applied to the Arctic Ocean to simulate tides with a horizontal resolution ranging from 1 km in the near‐coastal areas to 15 km in the deep ocean. By accurately resolving the irregular coastlines and bathymetry in the Arctic Ocean coastal regions, this model reproduces the diurnal (K1 and O1) and semidiurnal (M2 and S2) tidal wave dynamics and captures the complex tidal structure along the coast, particularly in the narrow straits of the Canadian Archipelago. The simulated tidal parameters (harmonic constituents of sea surface elevation and currents) agree well with the available observational data. High‐resolution meshes over the continental shelf and slope capture the detailed spatial structure of topographic trapped shelf waves, which are quite energetic along the Greenland, Siberia, and Spitsbergen continental slope and shelf break areas. Water stratification influences the vertical distribution of tidal currents but not the water transport and thus tidal elevation. The comparison with previous finite difference models suggests that horizontal resolution and geometric fitting are two prerequisites to simulate realistically the tidal energy flux in the Arctic Ocean, particularly in the Canadian Archipelago.
[1] A sea ice model was developed by converting the Community Ice Code (CICE) into an unstructured-grid, finite-volume version (named UG-CICE). The governing equations were discretized with flux forms over control volumes in the computational domain configured with nonoverlapped triangular meshes in the horizontal and solved using a second-order accurate finite-volume solver. Implementing UG-CICE into the Arctic Ocean finite-volume community ocean model provides a new unstructured-grid, MPI-parallelized model system to resolve the ice-ocean interaction dynamics that frequently occur over complex irregular coastal geometries and steep bottom slopes. UG-CICE was first validated for three benchmark test problems to ensure its capability of repeating the ice dynamics features found in CICE and then for sea ice simulation in the Arctic Ocean under climatologic forcing conditions. The model-data comparison results demonstrate that UG-CICE is robust enough to simulate the seasonal variability of the sea ice concentration, ice coverage, and ice drifting in the Arctic Ocean and adjacent coastal regions.
47 48 A high-resolution unstructured-grid global-regional nested ice-current coupled 49 FVCOM system was configured for the Arctic Ocean and used to examine the impact of 50 model resolution and geometrical fitting on the basin-coastal scale circulation and 51 transport in the pan-Arctic. With resolving steep bottom slope and irregular coastal 52 geometry, the model was capable of simulating the multi-scale circulation and its spatial 53 variability in the Arctic Basin and flow through the Bering Strait, Fram Strait and 54 Canadian Archipelago. The model-simulated annual-mean velocities were in good 55 agreement with observations within the measurement uncertainty and variability due to 56 insufficient sampling. The errors in the flow direction varied with the flow speed, larger 57 in the weak velocity zone and smaller as the velocity increased. In the upper 50-m layer, 58 the annual-mean circulation pattern was dominated by the wind-and ice-drifting-induced 59 anticyclonic circulation in the Arctic Basin and a relatively strong cyclonic slope current 60 along the edge of the continental shelf. In the deep 200-600-m layer, a relatively 61 permanent cyclonic circulation occurred along the steep bottom slope. These annual-62 mean circulations accounted for ~85% of the total kinetic energy variance. De-trending 63 the mean flow, an empirical orthogonal function (EOF) analysis showed that the semi-64 annual and seasonal variability of the sub-tidal flow was dominated by the first and 65 second modes that accounted for ~46% and ~30% of the total variance in the upper 50-m 66 layer and ~58% and 20% in the deep 200-600-m layer. Consistent with observations, the 67 AO-FVCOM-simulated cyclonic slope flow was characterized by a large positive 68 topostrophy. Sensitivity experiment results with various grid configurations suggested 69 that the currents over slopes, narrow straits and water passages featured topographic and 70 3 baroclinic frontal dynamical scales associated with bathymetric slope and internal Rossby 71 deformation radius. Over the Arctic slope, since these two scales are in the same order, 72 the along-slope current could be captured, as the cross-isobath model resolution was 73 refined to resolve the steep bottom topography. Under this condition, there is no need to 74 add Neptune forcing into the momentum equations. The accuracy of the estimation of the 75 transport through the strait and narrow water passage was affected by the model 76 resolution. In Fram Strait where the flow is characterized by strong lateral current shear 77 resulting from the Atlantic inflow and Arctic outflow, the transport estimation could have 78 a significant uncertainty due to both horizontal and vertical sampling resolutions.
Eighteen polycyclic aromatic hydrocarbons (PAHs) were measured in surficial sediments along a marine transect from the North Pacific into the Arctic Ocean. The highest average Σ 18 PAHs concentrations were observed along the continental slope of the Canada Basin in the Arctic (68.3 ± 8.5 ng g-1 dw), followed by sediments in the Chukchi Sea shelf (49.7 ± 21.2 ng g-1 dw) and Bering Sea (39.5 ± 11.3 ng g-1 dw), while the Bering Strait (16.8 ± 7.1 ng g-1 dw) and Central Arctic Ocean sediments (13.1 ± 9.6 ng g-1 dw) had relatively lower average concentrations. The use of principal components analysis with multiple linear regression (PCA/MLR) indicated that on average oil related or petrogenic sources contributed ~42% of the measured PAHs in the sediments and marked by higher concentrations of two methylnaphthalenes over the non-alkylated parent PAH, naphthalene. Wood and coal combustion contributed ~32%, and high temperature pyrogenic sources contributing ~26%. Petrogenic sources, such as oil seeps, allochthonous coal and coastally eroded material such as terrigenous sediments particularly affected the Chukchi Sea shelf and slope of the Canada Basin, while biomass and coal combustion sources appeared to have greater influence in the central Arctic Ocean, possibly due to the effects of episodic summertime forest fires.
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