台湾海峡三维风海流的数值模拟

本文利用POM模式模拟了季风在台湾海峡引起的风海流以及三维流场结构。在冬季和夏季两种条件下，得出了季风引起的水位变化和三维流场结构。结果显示在冬季季风的作用下，海峡的东部北部发生减水而西南部产生增水；在夏季海峡北部产生增水而东南部和西南部产生减水，在科氏力的作用下，风海流表层流向偏于风向右侧。风海流在20m处形成的流场和底层流场本文也给出了模拟结果。流速的艾克曼螺线显示；该海域的流速并不随水深加大而一致减小，而是先减小至一定深度再稍微增大，然后继结衰减而零。     

Transition of Tidal Waves from the East to South China Seas over the Taiwan Strait: Influence of the Abrupt Step in the Topography

Observations of tidal waves between the East and South China Seas (ECS and SCS) over the Taiwan Strait (TS) suggest that the diurnal tides simply appear as one southward-propagating wave from the ECS to the SCS through the TS. The semidiurnal tides, however, behave differently in that they appear as a southward-propagating Kelvin wave in the western TS and a nearly standing wave in the eastern TS, and then diminish rapidly over the shallow shoal in the southern TS. A smaller-domain model, with sea-level boundary conditions derived from a larger-domain tidal model, was first used to simulate tides in the TS to an overall percentage of accuracy of about 90%. Subsequent numerical experiments and theoretical analysis revealed that the southward-propagating semidiurnal tides to be impeded and then reflected as they arrive at an abrupt, deepened step in the topography of the southern TS. This reflection enhances the amplitudes of the incident semidiurnal tides and contributes to the formation of a nearly standing wave in the eastern TS. The southward-propagating diurnal tides in the TS are connected by the diurnal tides in the northern SCS when the amplitudes of the two tide systems are comparable and their phases nearly equal at the step. This revised version was published online in July 2006 with corrections to the Cover Date.     

Optimal estimation of absolute geostrophic velocity field in vicinity of the Luzon Strait using variational data assimilation technique

A P - vector method is optimized using the variational data assimilation technique(VDAT). The absolute geostrophic velocity fields in the vicinity of the Luzon Strait (LS) are calculated, the spatial structures and seasonal variations of the absolute geostrophic velocity field are investigated. Our results show that the Kuroshio enters the South China Sea (SCS) in the south and middle of the Luzon Strait and flows out in the north, so the Kuroshio makes a slight clockwise curve in the Luzon Strait, and the curve is strong in winter and weak in summer. During the winter, a westward current appears in the surface, and locates at the west of the Luzon Strait. It is the north part of a cyclonic gyre which exits in the northeast of the SCS; an anti-cyclonic gyre occurs on the intermediate level, and it exits in the northeast of the SCS, and an eastward current exits in the southeast of the anti-cyclonic gyre.     

浙闽沿海和台湾海峡海域冬季大风风速计算方法探讨

本文利用东海区海陆大风对比试验结果及26艘船只两个月的海上航测实况资料，通过对各种风速进行海陆比值分析、差值分析和测站间对比分析。论证了据陆上大风推算该海区大风风速计算式的可靠性，从而为实时、定量地预报海区大风提供了1种方法．     

1998年8月台湾海峡温度和叶绿素a含量的垂直分布特征

根据1998年8月台湾海峡温度、盐度、叶绿素a的观测结果，讨论了调查期间叶绿素a的垂直分布特征，结果表明，夏季台湾海峡西部海域存在明显的上升流，较高的叶绿素a含量均位于低温高盐的涌升水中，叶绿素a最大值出现存在上升流区边缘、温跃层附近，台湾海峡东部海域由高温、低盐、低营养盐水占据，叶绿素a含量明显较海峡西部海域低。     

Drifter Observations of Anticyclonic Eddies near Bussol' Strait, the Kuril Islands

Hydrographic surveys and satellite imaging reveal that mesoscale anticyclonic (AC) eddies are common features of the area south of Bussol' Strait, the deepest of the Kuril straits connecting the western North Pacific and Sea of Okhotsk. To examine the velocity structure of these eddies, we deployed groups of 15-m drogued satellite-tracked surface drifters over the Kuril-Kamchatka Trench in the fall of 1990 and late summer of 1993. Drifters in both groups entered large AC eddies centered over the axis of the trench seaward of Bussol' Strait and subsequently underwent a slow northeastward translation. One drifter (Drifter 1315) deployed near the center of the “Bussol' eddy” in 1990, remained in the eddy for roughly 45 days and made five loops at successively greater distances from the eddy center. Large-amplitude (80–100 cm/s) storm-generated inertial oscillations were observed during the first two loops. The vorticity field associated with the eddy resulted in a Doppler “red-shift” of inertial frequency motions such that the “effective” inertial period of 21 hours was roughly 4 hours greater than the nominal inertial period for the drifter latitude (45°N). In 1993, a second drifter (Drifter 15371) was retained in the Bussol' eddy for about 40 days. This eddy had characteristics similar to those of the 1990 eddy but was devoid of significant high-frequency motions until the drifter's final half loop. The observed spatial scales, persistence, and slow poleward translation of the eddies suggests that they play an important role in the dynamics of the East Kamchatka and Oyashio current systems. This revised version was published online in August 2006 with corrections to the Cover Date.     

Stable carbon and nitrogen isotopes of sinking particles in the eastern bransfield strait (Antarctica)

A time-series sediment trap was deployed at 1,034 m water depth in the eastern Bransfield Strait for a complete year from December 25, 1998 to December 24, 1999. About 99% of total mass flux was trapped during an austral summer, showing distinct seasonal variation. Biogenic particles (biogenic opal, particulate organic carbon, and calcium carbonate) account for about two thirds of annual total mass flux (49.2 g m^-2), among which biogenic opal flux is the most dominant (42% of the total flux). A positive relationship (except January) between biogenic opal and total organic carbon fluxes suggests that these two variables were coupled, due to the surface-water production (mainly diatoms). The relatively low δ¹³C values of settling particles result from effects on C-fixation processes at low temperature and the high CO² availability to phytoplankton. The correspondingly low δ¹⁵N values are due to intense and steady input of nitrates into surface waters, reflecting an unlikely nitrate isotope fractionation by degree of surface-water production. The δ¹⁵N and δ¹³C values of sinking particles increased from the beginning to the end of a presumed phytoplankton bloom, except for anomalous δ¹⁵N values. Krill and the zooplankton fecal pellets, the most important carriers of sinking particles, may have contributed gradually to the increasing δ¹³C values towards the unproductive period through the biomodification of the δ¹³C values in the food web, respiring preferentially and selectively¹²C atoms. Correspondingly, the increasing δ¹⁵N values in the intermediate-water trap are likely associated with a switch in source from diatom aggregates to some remains of zooplankton, because organic matter dominated by diatom may be more liable and prone to remineralization, leading to greater isotopic alteration. In particular, the tendency for abnormally high δ¹⁵N values in February seems to be enigmatic. A specific species dominancy during the production may be suggested as a possible and speculative reason.     

积云对流参数化方案模拟我国东南沿海及台湾海峡地区降水的适用性

我国东南沿海及台湾海峡地区地形和下垫面情况复杂,积云对流活动强烈,这给该地区降水的模拟和预测带来很大困难。为探讨不同积云对流参数化方案在我国东南沿海及台湾海峡地区的适用性,选择了4种参数化方案(Anthes-Kuo方案、Arakawa-Schubert方案、Fritsch-Chappell方案和MIT-Emanuel方案),基于区域气候模式RegCM 4.0分别模拟了该地区的降水情况,并选用了与模式分辨率相当的TRMM(Tropical Rainfall Measuring Mission,0.25°×0.25°)月平均降水资料进行验证。模拟结果表明,4种方案均能大致模拟出我国东南沿海及台湾海峡地区降水的空间结构和季节变化特征。其中,Fritsch-Chappell方案和MIT-Emanuel方案均能较好地模拟出降水空间分布,包括台湾岛南部和广东沿海的降水极值中心,而MIT-Emanuel方案降水的季节和年际变化特征模拟最好,如能够基本再现夏季降水在6月和8月份的双峰结构。此外,基于各高度层假相当位温的计算结果表明,MIT-Emanuel方案模拟的对流活动强烈,产生的对流性降水较多,使得其模拟的降水量值更接近实测资料。因此,MIT-Emanuel方案可能是最适用于模拟我国东南沿海和台湾海峡地区降水的积云对流参数化方案。     

南极布兰斯菲尔德海峡及邻区地壳结构反演及构造解析

南极布兰斯菲尔德海峡及邻区是南极半岛海域火山、地震等新构造运动最活跃的地区,由于前人对资料处理解释的差异,导致盆地的构造格局仍部分存疑。本文以研究区的卫星重力数据为基础,以多道反射地震和部分岩性资料为约束,采用重震联合反演方法构建了三条横跨研究区的地壳结构剖面,并进一步研究布兰斯菲尔德海峡盆地的地壳结构。研究结果表明布兰斯菲尔德海峡盆地莫霍面深度为33—38km。菲尼克斯板块俯冲消减下沉至南设得兰岛弧之下,导致南设得兰海沟的俯冲带后撤,产生3—4km厚的岩浆混染地壳,密度为2.9g/cm³。分析认为受板块运动和弧后扩张影响,沿布兰斯菲尔德海峡盆地扩张脊分布的海底火山裂隙式喷发,并进一步导致盆地的持续性扩张。     

Basin-scale seawater lead isotopic character and its geological evolution indicated by Fe-Mn deposits in the SCS

Abstract

The geochemical characteristics and Pb isotope variations in Fe-Mn deposits collected from the South China Sea (SCS) were studied in this paper. The mineralogical and chemical composition data indicate that the deposits are almost all hydrogenetic in origin. Compared with the Fe-Mn deposits in other oceans, the SCS Fe-Mn deposits have a significantly higher Pb content because of higher material supply in addition to a lower growth rate of the deposits. Pb isotope ratios in the surface of the SCS Fe-Mn deposits are relatively uniform, with a characteristic of relatively lower ²⁰⁶Pb/²⁰⁴Pb ratio. The Pb isotopic compositions of the SCS Fe-Mn deposits are controlled by the Pacific Deep Water and local inputs, which include eolian dust from the Asian continent and weathering products from Taiwan, Luzon and SCS submarine volcanic rocks. The continuously increasing ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb ratios along the transect of nodule D581 over the past 3.5?Ma are affected by the stepwise closure of the Luzon Strait that reduced volcanic material supply and the deep current strengthen at the same time.