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1.
A model study is conducted to examine the role of Pacific water in the dramatic retreat of arctic sea ice during summer 2007. The model generally agrees with the observations in showing considerable seasonal and interannual variability of the Pacific water inflow at Bering Strait in response to changes in atmospheric circulation. During summer 2007 anomalously strong southerly winds over the PaCific sector of the Arctic Ocean strengthen the ocean circulation and bring more Pacific water into the Arctic than the recent （2000-2006） average. The simulated summer （3 months ） 2007 mean Pacific water inflow at Bering Strait is 1.2 Sv, which is the highest in the past three decades of the simulation and is 20% higher than the recent average. Particularly, the Pacific water inflow in September 2007 is about 0.5 Sv or 50% above the 2000-2006 average. The strengthened warm Pacific water inflow carries an additional 1.0 x 1020 Joules of heat into the Arctic, enough to melt an additional 0.5 m of ice over the whole Chukchi Sea. In the model the extra summer oceanic heat brought in by the Pacific water mainly stays in the Chukchi and Beaufort region, contributing to the warming of surface waters in that region. The heat is in constant contact with the ice cover in the region in July through September. Thus the Pacific water plays a role in ice melting in the Chukchi and Beaufort region all summer long in 2007, likely contributing to up to O. 5 m per month additional ice melting in some area of that region.  相似文献   

2.
Totally 2472 grains of Radiolaria belonging to 36 Genera and 45 species are distinguished from 12 surface sediments in the Bering Sea. The distribution characteristics of Radiolaria fossils in the surface sediments are as follows: (1) From the shelf of shallow water to the upper of continental slope, there are a few Radiolaria fossils and monotonous genus and species; (2) In the lower of continental slope, Radiolaria fossils are poor in the volcanic cinders and turbidite; (3) The abundance and diversity of Radiolaria fossils are high in clay of the basin. The dominant species of Radiolaria is Spongotrochus glacialis on the continental shelf. Current, topography, water depth, and temperature etc. are key factors influencing Radiolaria distribution. The sources of sediments mainly are terrigenous, biogenic and volcanic sediments in the survey area and they are mostly from the Kamchatka peninsula in the east of Russia and the Aleutian Islands.  相似文献   

3.
In this paper, the authors used the Princeton Ocean Model (POM) to simulate the seasonal evolutions of circulation and thermal structure in the Yellow Sea. The simulated circulation showed that the Yellow Sea Warm Current (YSWC) was a compensation current of monsoon-driven current, and that in winter, the YSWC became stronger with depth, and could flow across the Bohai Strait in the north. Sensitivity and controlling tests led to the following conclusions, In winter, the direction of the Yellow Sea Coastal Current in the surface layer was controlled partly by tide instead of wind, In summer, a cyclonic horizontal gyre existed in the middle and eastern parts of the Yellow Sea below 10 m. The downwelling in upper layer and upwelling in lower layer were somehow similar to Hu et al. (1991) conceptual model. The calculated thermal structure showed an obvious northward extending YSWC tongue in winter, its position and coverage of the Yellow Sea Cold Water Mass in summer.  相似文献   

4.
For understanding more about the water exchange between the Kuroshio and the East China Sea,We studied the variability of the Kuroshio in the East China Sea(ECS) in the period of 1991 to 2008 using a three-dimensional circulation model,and calculated Kuroshio onshore volume transport in the ECS at the minimum of 0.48 Sv(1 Sv ;106 m3/s) in summer and the maximum of 1.69 Sv in winter.Based on the data of WOA05 and NCEP,The modeled result indicates that the Kuroshio transport east of Taiwan Island decreased since 2000.Lateral movements tended to be stronger at two ends of the Kuroshio in the ECS than that of the middle segment.In addition,we applied a spectral mixture model(SMM) to determine the exchange zone between the Kuroshio and the shelf water of the ECS.The result reveals a significantly negative correlation(coefficient of-0.78) between the area of exchange zone and the Kuroshio onshore transport at 200 m isobath in the ECS.This conclusion brings a new view for the water exchange between the Kuroshio and the East China Sea.Additional to annual and semi-annual signals,intra-seasonal signal of probably the Pacific origin may trigger the events of Kuroshio intrusion and exchange in the ECS.  相似文献   

5.
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6.
An MOM2 based 3-dimentional prognostic baroclinic Z-ordinate model was established to study the circulation in eastern China seas, considering the topography, inflow and outflow on the open boundary, wind stress, temperature and salinity exchange on the sea surface. The results were consistent with observation and showed that the Kuroshio intrudes in large scale into the East China Sea continental shelf East China, during which its water is exchanged ceaselessly with outer sea water along Ryukyu Island. The Tsushima Warm Current is derived from several sources, a branch of the Kuroshio, part of the Taiwan Warm Current, and Yellow Sea mixed water coming from the west of Cheju Island. The water from the west of Cheju Island contributes approximately 13% of the Isushima Warm Current total transport through the Korea Strait. The circulation in the Bohai Sea and Yellow Sea is basically cyclonic circulation, and is comprised of coastal currents and the Yellow Sea Warm Current. Besides simulation of the real circulation, numerical experiments were conducted to study the dynamic mechanism. The numerical experiments indicated that wind directly drives the East China Sea and Yellow Sea Coastal Currents, and strengthens the Korea Coastal Current and Yellow Sea Warm Current. In the no wind case, the kinetic energy of the coastal current area and main YSWC area is only 1% of that of the wind case.Numerical experiments also showed that the Tsushima Warm Current is of great importance to the formation of the Korea Coastal Current and Yellow Sea Warm Current.  相似文献   

7.
The sea ice cover in the Arctic Ocean has been reducing and hit the low record in the summer of 2007. The anomaly was extremely large in the Pacific sector. The sea level height in the Bering Sea vs. the Greenland Sea has been analyzed and compared with the current meter data through the Bering Strait. A recent peak existed as a consequence of atmospheric circulation and is considered to contribute to inflow of the Pacific Water into the Arctic Basin. The timing of the Pacific Water inflow matched with the sea ice reduction in the Pacific sector and suggests a significant increase in heat flux. This component should be included in the model prediction for answering the question when the Arctic sea ice becomes a seasonal ice cover.  相似文献   

8.
While the Antarctic Slope Current(ASC) has been intensively studied for the East Antarctica slope area and the Weddell Sea, its fate in the western Antarctic Peninsula(WAP) region remains much less known. Data from two cruises conducted near the South Shetland Islands(SSIs) and the Elephant Island(EI), one in austral summer of 2004 and one in austral winter of 2006, were analyzed to provide a broad picture of the circulation pattern over the continental slope of the surveyed area, and an insight into the dynamical balance of the circulation. The results indicate that southwestward currents are present over the upper slope in the study area, indicating the ASC in the WAP region. Near the Shackleton Gap(SG) north of the EI, the southwestward slope currents near the shelf break are characterized by a water mass colder and fresher than the ambient water, which produces cross-slope density gradients and then vertical shear of the along-slope(or along-isobath) velocity. The vertical shear is associated with a reversal of the along-slope current from northeastward at surface to southwestward in deeper layers, or a depth-intensification of the southwestward slope currents. The water mass with temperature and salinity characteristics similar to the observed cold and fresh water is also revealed on the southern slope of the Scotia Sea, suggesting that this cold and fresh water is originated from the Scotia Sea slope and flows southwestward through the SG. Over the shelf north of the SSIs, the cold and fresh water mass is also observed and originates mainly from the Bransfield Strait. In this area, vertical structure of the southwestward slope currents is associated with the onshore intrusion of the upper Circumpolar Deep Water that creates cross-slope density gradients.  相似文献   

9.
Using hydrographic data covering large areas of ocean for the period from June 21 to July 5 in 2009,we studied the circulation structure in the Luzon Strait area,examined the routes of water exchange between the South China Sea(SCS) and the Philippine Sea,and estimated the volume transport through Luzon Strait.We found that the Kuroshio axis follows a e-shaped path slightly east of 121uE in the upper layer.With an increase in depth,the Kuroshio axis became gradually farther from the island of Luzon.To study the water exchange between the Philippine Sea and the SCS,identification of inflows and outflows is necessary.We first identified which flows contributed to the water exchange through Luzon Strait,which differs from the approach taken in previous studies.We determined that the obvious water exchange is in the section of 121°E.The westward inflow from the Philippine Sea into the SCS is 6.39 Sv in volume,and mainly in the 100±500 m layer at 19.5°±20°N(accounting for 4.40 Sv),while the outflow from the SCS into the Philippine Sea is concentrated in the upper 100 m at 19°±20°N and upper 400 m at 21°±21.5°N,and below 240 m at 19°±19.5°N,accounting for 1.07,3.02 and 3.43 Sv in volume transport,respectively.  相似文献   

10.
Nitrate is considered the nutrient that limits new primary production in the southeastern Bering Sea shelf. Nitrate regenerated through biological nitrification has the potential to significantly support primary production as well. Here we use measurements of the specific rate of water column nitrification in a 1-D ecosystem model to quantify the resupply of nitrate from nitrification in the middle shelf of the southeastern Bering Sea. Model sensitivity studies reveal nitrification rate is an important control on the dominant phytoplankton functional type, and the amount of nitrate in su mer bottom waters and in the winter water column. Evaluation of nitrification using the model supports the hypothesis that increases in late-summer nitrate concentrations observed in the southeastern Bering Sea bottom waters are due to nitrification. Model results for nitrate replenishment exceed previously estimated rates of 20-30% based on observations. The results of this study indicate that nitrification, potentially the source of up to - 38% of the springtime water column nitrate, could support - 24% of the annual primary production.  相似文献   

11.
Historical hydrographic data across several sections in the South China Sea (SCS) and Taiwan Strait have been reconsidered. The year-around existence of the South China Sea Warm Current (SCSWC) along the shelf break off the Guangdong coast and the seemingly year-around southwestward current to the east of SCSWC are both evident in the data. The data also showed that the northward current in the Taiwan Strait seemed to be the extension of SCSWC. A barotropic numerical model is employed to explain some of the observed features. Reasonable simulation of the circulation in the northeast part of SCS has been found.  相似文献   

12.
A high-resolution Arctic Ocean-Finite Volume Community Ocean Model(AO-FVCOM) and observational current data from 14 mooring stations in Bering Strait and surrounding regions between 1990 and 2015 were used to study the seasonal and interannual variability of Bering Strait throughflow(BST). AO-FVCOM represented the BST with a climatological northward flux of 1.06 Sv, which was close to the observational mean of 0.94 ? 0.26 Sv. From the model results, the strongest volume flux was in summer, approximately 45% larger than that in winter. Interannual variability of BST was also indicated in the model results, and the maximum and minimum annual mean transports are in 2007 and 2012, respectively. AO-FVCOM showed larger differences from the observations in 2000, 2002, and 2015 than in other years, which may be related to the limitation of atmospheric forcing for the model. According to the driving mechanisms of BST, sea level difference(SLD) across the strait dominates the northward volume transport, and local wind is also important in forcing the seasonal variability of the BST and SLD patterns to change the BST indirectly.  相似文献   

13.
A 3.8-kin Coupled Ice-Ocean Model （C1OM） was implemented to successfully reproduce many observed phenomena in the Beaufort and Chukchi seas, including the Bering-inflow-originated coastal current that splits into three branches： Alaska Coastal Water （ACW） , Central Channel, and Herald Valley branches. Other modeled phenomena include the Beaufort Slope Current （BSC） , the Beaufort Gyre, the East Siberian Current （ ESC）, mesoscale eddies, seasonal landfast ice, sea ice ridging, shear, and deformation. Many of these downscaling processes can only be captured by using a high-resolution CIOM, nested in a global climate model. The seasonal cycles for sea ice concentration, thickness, velocity, and other variables are well reproduced with Solid validation by satellite measurements. The seasonal cycles for upper ocean dynamics and thermodynamics are also well reproduced, which include the formation of the cold saline layer due to the injection of salt during sea ice formation, the BSC, and the subsurface upwelling in winter that brings up warm, even more saline Atlantic Water along the shelfbreak and shelf along the Beaufort coast.  相似文献   

14.
Inter-annual variability of the Kuroshio water intrusion on the shelf of East China Sea (ECS) was simulated with a nested global and Northwest Pacific ocean circulation model. The model analysis reveals the influence of the variability of Kuroshio transport east of Taiwan on the intrusion to the northeast of Taiwan: high correlation (r = 0.92) with the on-shore volume flux in the lower layer (50–200 m); low correlation (r = 0.50) with the on-shore flux in the upper layer (0–50 m). Spatial distribution of correlations between volume fluxes and sea surface height suggests that inter-annual variability of the Kuroshio flux east of Taiwan and its subsurface water intruding to the shelf lag behind the sea surface height anomalies in the central Pacific at 162°E by about 14 months, and could be related to wind-forced variation in the interior North Pacific that propagates westward as Rossby waves. The intrusion of Kuroshio surface water is also influenced by local winds. The intruding Kuroshio subsurface water causes variations of temperature and salinity of bottom waters on the southern ECS shelf. The influence of the intruding Kuroshio subsurface water extends widely from the shelf slope northeast of Taiwan northward to the central ECS near the 60 m isobath, and northeastward to the region near the 90 m isobath.  相似文献   

15.
Impact of Kuroshio on the dissolved oxygen in the East China Sea region   总被引：1，自引：0，他引：1  
A marine survey was conducted from 18 May to 13 June 2014 in the East China Sea(ECS)and its adjacent Kuroshio Current to examine the spatial distribution and biogeochemical characteristics of dissolved oxygen(DO) in spring. Waters were sampled at 10-25 m intervals within 100 m depth, and at 25-500 m beyond 100 m. The depth, temperature, salinity, and density(sigma-t) were measured in situ with a conductivity-temperature-depth(CTD) sensor. DO concentrations were determined on board using traditional Winkler titration method. The results show that in the Kuroshio Current, DO content was the highest in the euphotic layer, then decreased sharply with depth to about 1 000 m, and increased with depth gradually thereafter. While in the ECS continental shelf area, DO content had high values in the coastal surface water and low values in the near-bottom water. In addition, a low-DO zone of f the Changjiang(Yangtze) River estuary was found in spring 2014, and it was formed under the combined influence of many factors, including water stratification, high primary productivity in the euphotic layers, high accumulation/sedimentation of organic matter below the euphotic layers, and mixing/transport of oceanic current waters on the shelf. Most notable among these is the Kuroshio intruded water, an oceanic current water which carried rich dissolved oxygen onto the continental shelf and alleviated the oxygen deficit phenomenon in the ECS, could impact the position, range, and intensity, thus the formation/destruction of the ECS Hypoxia Zone.  相似文献   

16.
The nonwind-driven mechanism of the winter circulation in the northern South China Sea is discussed. Linked by the Bashi Strait to the Pacific Ocean, the northern South Cnina Sea is treated as a part of the Pacific western boundary where the circulation variation (except the very thin surface layer) is closely related to that of the ocean interior and the effect of local wind might be neglected (at least for some seasons). Based on the assumption that the thick and strong westward current which flows in through the Bashi Strait can effectively prevent water exchange between the northern and southern South China Seas, the model sea only includes the northern part. Barotropic numerical experiments show that part of this westward current is deflected by the continental slope and forms the slope area NE current—the South China Sea Warm Current. Besides, the topographical flow fed by the extension of the western boundary current and the anticyclonic eddy born near the eastern boundary are also fundamental components of the South China Sea Warm Current. The reflection of the incident Rossby waves by the continental slope is found to be of significance in the intensification of the South China Sea Warm Current. Contribution No. 1362 from Institute of Oceanology, Academia  相似文献   

17.
Based on the field data obtained during cruises on the shelf of the East China Sea from 1997 to 1999, seasonal variations of coastal upwelling on the inner shelf are discussed by using cross-shelf transect profiles and horizontal distributions of chemical and hydrographic variables. Results show that the coastal upwelling was year-round, but the areas and intensities of the upwelling were quite different in season. The coastal upwelling occurred in all of the coastal areas of the region in spring and summer, but in autumn only in the area off Zhejiang Province, and in winter in the area off Fujian Prov- ince. It was the strongest in summer and the weakest in winter. Geographically, it was the strongest in the area off Zhejiang Province and the weakest in the southmost or northmost parts of the East China Sea. The estimated nutrient fluxes upward into euphotic zone through coastal upwelling were quite large, es- pecially for phosphate, which contributed significantly to primary production and improved the nutrient structure of the coastal ecosystem in the East China Sea.  相似文献   

18.
We present a three-level nested-grid ocean circulation modeling system for the Belize shelf of the western Caribbean Sea. The nested-grid system has three subcomponents： a coarse-resolution outer model of the western Caribbean Sea; an intermediate-resolution middle model of the southern Mest〉American Barrier Reef System; and a fine-resolution inner model of the Belize shelf. The two-way nesting technique based on the semi-prognostic method is used to exchange information between the three subcomponents. We discuss two applications of the nested-grid system in this study. In the first application we simulate the seasonal mean circulation in the region, with the nested system forced by monthly mean surface fluxes and boundary forcing. The model results reproduce the general circulation features on the western Caribbean Sea and mest〉scale circulation features on the Belize shelf. In the second application, we simulate the storm-induced circulation during Hurricane Mitch in 1998, with the nested-grid system forced by the combination of monthly mean forcing and idealized wind stress associated with the storm. The model results demonstrate that the storm-induced currents transport a large amount of estuarine waters from coastal regions of Honduras and Guatemala to offshore reef atolls.  相似文献   

19.
The Bering Sea circulation is derived as a variational inverse of hydrographic profiles（ temperature and salinity） , atmospheric climatologies and historical observation of ocean curents. The important result of this study is estimate of the mean climatological sea surface height （SSH） that can be used as a reference for satellite altimetry sea level anomaly data in the Bering Sea region. Numerical experiments reveal that, when combined with satellite altimetry, the obtained reference SSH effectively constrains a realistic reconstruction of the Amukta Pass circulation.  相似文献   

20.
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