The main phosphorous sources in the Changjiang estuary

Analysis using historical data on the phosphate sources in Changjiang （Yangtze River） estuary show that phosphate was supplied equally from the east, south, west and north of the estuary. These sources include the Changjiang River, the Taiwan Warm Current （TWC）, a cyclone-type eddy, and the 32°N Upwelling, supplying different phosphates in different times, ways and intensities. The magnitude of their supplying phosphate concentration was related with the size in the order of the Changjiang River 〈 the TWC 〈 the 32°N Upwelling 〈 the cyclone-type eddy, and the duration of the supplying was： the Changjiang River 〉 the TWC 〉 the cyclone-type eddy 〉 the 32°N Upwelling. The four sources supplied a great deal of phosphate so that the phosphate concentration in the estuary was kept above 0.2 pmol/L in previous years, satisfying the phytoplankton growth. The horizontal and vertical distribution of the phosphate concentration showed that near shallow marine areas at 122°E/31°N, the TWC in low nutrient concentration became an upwelling through sea bottom and brought up nutrients from sea bottom to marine surface. In addition, horizontal distribution of phosphate concentration was consistent with that of algae： Rhizosolenia robusta, Rhizosolenia calcaravis and Skeletonema, which showed that no matter during high water or low water of Changjiang River, these species brought by the TWC became predominant species. Therefore, the authors believe that the TWC flowed from south to north along the coast and played a role in deflecting the Changjiang River flow from the southern side.     

深水沉积研究前缘问题

深水沉积研究经历了50年,争论也持续了50年。从浊流及鲍玛序列开始,随着对浊流定义的过分使用,到今天对鲍玛序列作为浊积岩相序及相关的扇模式普遍持否定态度,深水沉积研究经历了一个认识的旋回。主要问题和争论的焦点是：是否所有深水砂岩都是浊流成因,鲍玛序列能否代表浊积岩相序;是否所有的深水扇水道下方都能形成席状的、平行的、加厚的、具有丘状外形的浊积砂岩沉积;是否可以利用地震方法识别深水扇的砂岩储层。对“浊流”概念的过分使用把深水扇模式内几乎所有深水沉积都解释成浊流成因,导致了曾经为之建立模式的学者纷纷撰文抛弃原有扇模式。深水沉积研究面临着对过往认识的否定和如何建立新的理论模式。尽管浊流及相关的深水扇模式研究走向穷途末路,石油工业却从浊流理论和相关模式中获得了许多油气发现,勘探家们仍然希望通过这些模式寻找更多的油气,科学理论和应用出现了分化。对深水沉积过程和流态的认识及沉积模式的建立是当今深水沉积研究的难点,实现深水砂岩储层的有效预测是深水沉积研究的主要目的。我国深海油气勘探在即,深水沉积的科学问题同样不可逾越。     

A Review on the Currents in the South China Sea: Seasonal Circulation, South China Sea Warm Current and Kuroshio Intrusion

Researches on the currents in the South China Sea (SCS) and the interaction between the SCS and its adjacent seas are reviewed. Overall seasonal circulation in the SCS is cyclonic in winter and anticyclonic in summer with a few stable eddies. The seasonal circulation is mostly driven by monsoon winds, and is related to water exchange between the SCS and the East China Sea through the Taiwan Strait, and between the SCS and the Kuroshio through the Luzon Strait. Seasonal characteristics of the South China Sea Warm Current in the northern SCS and the Kuroshio intrusion to the SCS are summarized in terms of the interaction between the SCS and its adjacent seas.     

黄河三角洲埕岛近岸海域悬浮泥沙运动

根据1998年9月8日和1999年3月19日两次对埕北海域进行的10个站位的同步海流、悬浮泥沙观测资料，进行该海区的悬浮泥沙输运趋势分析，发现该海区含沙量较大。从整个海区来看，底层含沙量大于表层含沙量，该海区泥沙含量普遍表现为东南部的泥沙含量高于西北部的泥沙含量；由单宽输沙量的计算及有关资料分析可以得出，秋季泥沙运移趋势是由东南向到西北向，而春季泥沙的运移趋势是由东北向到西南向；含沙量是随流速的加大而增加，含沙量的峰值稍滞后于流速的峰值；该海区为冲蚀海区，悬浮泥沙产生的平均年7中刷量为2cm／a，在本海区的地形塑造中占次要地位。     

The Taiwan-Tsushima Warm Current System: Its Path and the Transformation of the Water Mass in the East China Sea

Using a temperature data set from 1961 to 1990, we estimated the monthly distribution of the vertically integrated heat content in the East China Sea. We then drew the monthly map of the horizontal heat transport, which is obtained as the difference between the vertically integrated heat content and the surface heat flux. We anticipate that its distribution pattern is determined mainly due to the advection by the ocean current if it exists stably in the East China Sea. The monthly map of the horizontal heat transport showed the existence of the Taiwan-Tsushima Warm Current System (TTWCS) at least from April to August. The T-S (temperature-salinity) analysis along the path of TTWCS indicated that the TTWCS changes its T-S property as it flows in the East China Sea forming the Tsushima Warm Current water. The end members of the Tsushima Warm Current water detected in this study are water masses in the Taiwan Strait and the Kuroshio surface layer, the fresh water from the mainland of China, and the southern tip of the Yellow Sea Cold Water extending in the northern part of the East China Sea. This revised version was published online in August 2006 with corrections to the Cover Date.     

一种计算斜坡处海流的诊断模式

本文提出一种考虑底斜效应,适合斜坡处海流诊断计算的模式,并且分别计算了日本以南黑潮区部分测线和对马暖流流源区的流速。其结果与实测符合较好。     

历史的个人化与现时性--臧棣历史书写论

步入中年的北大诗人臧棣在断裂的诗史年代返身关注"历史",但这已不是往昔的传统主流历史,而是个人化、具体化、偶然化的历史,它以现在为起点,向过去、未来不断地延伸、重演,臧棣的诗歌因此表现出浓厚的历史维度和命运维度.     

Circulation in a Southern Italy coastal basin: Modelling and field measurements

The purpose of the present work is to study the hydrodynamic aspects in the Mar Piccolo, a coastal basin located on the northern side of the Gulf of Taranto in the Ionian Sea (Italy), by means of mathematical modelling and field measurements. The latter were assessed during three surveys carried out in the spring–summer of 2002. Collected data have been utilized as input by the 3-D Princeton Ocean Model, which is a sigma coordinate, free surface ocean model which was developed in the late 1970s by Blumberg and Mellor. Simulations in baroclinic condition were forced by a homogeneous and stationary wind field, a simple tidal wave, a constant outflow and vertical stratification of temperature and salinity. A comparison was made between the mathematical modelling results and the field measurements collected during the surveys, in terms of velocity. It was observed that during small tides, when the wind effect prevails over the stratification effect, the best model results were obtained for the most superficial layer and that superficial patterns reproduced by the model are more sensitive to wind direction than to stratification. On the contrary, when the wind effect decreases or the thermohaline effect rises, best results occurred in deeper layers.     

On stochastic stability of regional ocean models to finite-amplitude perturbations of initial conditions

We consider error propagation near an unstable equilibrium state (classified as an unstable focus) for spatially uncorrelated and correlated finite-amplitude initial perturbations using short- (up to several weeks) and intermediate (up to 2 months) range forecast ensembles produced by a barotropic regional ocean model. An ensemble of initial perturbations is generated by the Latin Hypercube design strategy, and its optimal size is estimated through the Kullback–Liebler distance (the relative entropy). Although the ocean model is simple, the prediction error (PE) demonstrates non-trivial behavior similar to that existing in 3D ocean circulation models. In particular, in the limit of zero horizontal viscosity, the PE at first decays with time for all scales due to dissipation caused by non-linear bottom friction, and then grows faster than (quasi)-exponentially. Statistics of a prediction time scale (the irreversible predictability time (IPT)) quickly depart from Gaussian (the linear predictability regime) and becomes Weibullian (the non-linear predictability regime) as amplitude of initial perturbations grows. A transition from linear to non-linear predictability is clearly detected by the specific behavior of IPT variance. A new analytical formula for the model predictability horizon is introduced and applied to estimate the limit of predictability for the ocean model.     

Paleoproductivity evolution off central Chile from the Last Glacial Maximum to the Early Holocene

A geochemical and paleontological reconstruction of paleoproductivity, upwelling intensity and sea surface temperature (SST) off central Chile at 35°S (GeoB3359-3) reveals marked changes from the Last Glacial Maximum (LGM) through the Early Holocene. Surface-water productivity was determined by the interaction between the atmospheric (the Southern Westerlies) and oceanographic (the Antarctic Circumpolar Current, ACC) systems from the LGM through early Termination I (TI). The northward shift of the climate zones during the LGM brought the ACC, as the main macronutrient source, closer to the GeoB3359-3, SST lowered, and surface water productivity and accumulation rates of biogenic components enhanced. With the poleward return of the Southern Westerlies and the ACC, the subtropical high-pressure system became the dominant atmospheric component southward till 35°S during the late TI and Early Holocene and caused surface water productivity to increase through enhanced upwelling.