The Yellow Sea Warm Current(YSWC) penetrates northward along the Yellow Sea Trough,and brings warm and saline water towards the Bohai Sea.The YSWC becomes much less intrusive in summer and is limited mostly in the southern trough,contrasting with a deep winter penetration well into the trough.The seasonal variability of the YSWC has prompted a debate regarding which controls the YSWC and its seasonal variability.In this article,the annual mean and seasonal variability of the YSWC was examined by using a 3-D ocean model together with several experiments.The results show that in the annual mean the YSWC is a compensating current firstly for the southward Korea Coastal Current(KCC),which is mainly caused by the Kuroshio Current(KC).The local wind-stress forcing plays an important but secondary role.However,the local monsoonal forcing plays a prominent role in modulating the seasonal variability.A deep northwestward intrusion of the YSWC in winter,for instance,is mainly due to a robustly developed China Coastal Current(CCC) which draws water along the Yellow Sea trough to feed a southward flow all the way from the Bohai Sea to the Taiwan Strait.
The Taiwan Warm Current (TWC) and the Tsushima Warm Current (TSWC) flow northward over the shelf in the East China Sea (ECS), which some previous studies regard as a Taiwan-Tsushima Warm Current (TTWC) System. But the roles of the TWC and TSWC in the formation of the TTWC system have not been clarified. This article will show that the TSWC is more important in the TTWC system. Using a three-dimensional baroclinic model, we conducted several numerical experiments to reveal the dynamic relationship between the TWC and TSWC. The results show that the TWC has little effect on the TSWC, while the TSWC has a significant effect on the TWC. A source-sink driven mechanism along isobaths may be used to explain this phenomenon. The perennial northward flow through the Tsushima Strait pumps the response over the northern shelf in the ECS that gives rise to the TWC. Although the TSWC is located at the "downstream" region, it could induce about 0.5 Sv to TWC in annual mean values.
基于国际Argo资料中心提供的从2004年1月至2007年10月的浮标剖面资料,对西北太平洋模态水的时空变化特征进行分析。结合WOA01(the World Ocean Atlas 2001)资料,选定模态水主要形成区(30°～35°N,140°～155°E)作为研究区域,利用3月份的平均资料,给出西北太平洋模态水的空间结构为:北边界位于34.5°N附近,南边界可达30°N以南,东边界位于151.5°E,西边界可达140°E以西,深度为350m以浅。通过对模态水核心区的逐月资料分析,揭示了其温度、盐度等的季节变化,并提出一种判别模态水范围的盐度判别法。结合海平面高度异常变化,初步分析了涡旋对模态水的影响,发现涡旋只能暂时改变核心区模态水的温盐结构,之后该区域模态水将基本恢复到正常状态。根据模态水2004-2007年的水文数据特点,发现在过去4a中模态水性质基本稳定,变化很小。
通过海气耦合模式CCSM3(The Community Climate System Model version 3),研究在北大西洋高纬度淡水强迫下,北太平洋冬季的海表温度SST、风场及流场的响应及其区域性差异。结果表明:淡水的注入使北太平洋整体变冷,但有部分区域异常增暖;在太平洋东部赤道两侧,SST的变化出现北负南正的偶极子型分布。阿留申低压北移的同时中纬度西风减弱,热带附近东北信风增强。黑潮和南赤道流减弱,北太平洋副热带逆流和北赤道流增强,日本海被南向流控制。风场及流场的改变共同导致了北太平洋SST异常出现复杂的空间差异:北太平洋中高纬度SST的降温主要由大气过程决定,海洋动力过程主要影响黑潮、日本海及副热带逆流区域的SST,太平洋热带地区SST异常由大气与海洋共同主导。
In this paper, we use the conductivity-temperature-depth (CTD) observation data and a three-dimensional ocean model in a seasonally-varying forcing field to study the barrier layer (BL) in the PN section in the East China Sea (ECS). The BL can be found along the PN section with obviously seasonal variability. In winter, spring and autumn, the BL occurs around the slope where the cold shelf water meets with the warm Kuroshio water. In summer, the BL can also be found in the shelf area near salinity front of the Changjiang (Yangtze) River Dilution Water (YRDW). Seasonal variations of BL in the PN section are caused by local hydrological characteristics and seasonal variations of atmospheric forcing. Strong vertical convection caused by sea surface cooling thickens the BL in winter and spring in the slope area. Due to the large discharge of Changjiang River in summer, the BL occurs extensively in the shelf region where the fresh YRDW and the salty bottom water meet and form a strong halocline above the seasonal thermocline. The formation mechanism of BL in the PN section can be explained by the vertical shear of different water masses, which is called the advection mechanism. The interannual variation of BL in summer is greatly affected by the YRDW. In the larger YRDW year (such as 1998), a shallow but much thicker BL existed on the shelf area.
Based on the Estuarine,Coastal and Ocean Modeling System with Sediments(ECOMSED) model,a 3-D hydrodynamic-transport numerical model was established for the offshore area near the Yangtze Estuary in the East China Sea.The hydrodynamic module was driven by tide and wind.Sediment module included sediment resuspension,transport and deposition of cohesive and non-cohesive sediment.The settling of cohesive sediment in the water column was modeled as a function of aggregation(flocculation) and deposition.The numerical results were compared with observation data for August,2006.It shows that the sediment concentration reduces gradually from the seashore to the offshore area.Numerical results of concentration time series in the observation stations show two peaks and two valleys,according with the observation data.It is mainly affected by tidal current.The suspended sediment concentration is related to the tidal current during a tidal cycle,and the maximum concentration appears 1h-4h after the current maximum velocity has reached.
By combining Argos drifter buoys and TOPEX/POSEIDON altimeter data, the time series of sea-surface velocity fields in the Kuroshio Current (KC) and adjacent regions are established. And the variability of the KC from the Luzon Strait to the Tokara Strait is studied based on the velocity fields. The results show that the dominant variability period varies in different segments of the KC: The primary period near the Luzon Strait and to the east of Taiwan Island is the intra-seasonal time scale; the KC on the continental shelf of the ECS is the steadiest segment without obvious periodicity, while the Tokara Strait shows the period of seasonal variability. The diverse periods are caused by the Rossby waves propagating from the interior ocean, with adjustments in topography of island chain and local wind stress.
