Ice Sheet-Thermohaline Circulation Interactions in a Climate Model of Intermediate Complexity   总被引：3，自引：0，他引：3  

Zhaomin Wang  Lawrence A. Mysak 《Journal of Oceanography》2001,57(4):481-494

A vertically integrated dynamic ice sheet model is coupled to the atmosphere-ocean-sea ice-land surface climate model recently developed by Wang and Mysak (2000). The background lateral (east-west) ice sheet discharge rate used by Gallee et al. (1992) is reduced and the planetary emissivity is increased (to parameterize the cooling effect of a decrease of the atmospheric CO₂ concentration), in order to build up substantial ice sheets during a glacial period and hence set the stage for ice sheet-thermohaline circulation (THC) interactions. The following iceberg calving scheme is then introduced: when the maximum model height of the North American ice sheet reaches a critical value (2400 m), a prescribed lateral discharged rate is imposed on top of the background discharge rate for a finite time. Per a small prescribed discharge rate, repeated small iceberg calving events occur, which lead to millennial-scale climate cycles with small amplitudes. These are a crude representation of Dansgaard-Oeschger oscillations. Over one such cycle, the zonally averaged January surface air temperature (SAT) drops about 1.5°C at 72.5°N. However, a large prescribed lateral discharge rate leads to the shut down of the THC. In this case, the January SAT drops about 5°C at 72.5°N, the sea ice extent advances equatorward from 57.5° to 47.5°N and the net ice accumulation rate at the grid of maximum ice sheet height is reduced from 0.24 to 0.15 m/y. Since data strongly suggest that a collapsed THC was not a steady state during the last glacial, we restore the THC by increasing the vertical diffusivity in the North Atlantic Ocean for a finite time. The resulting climate cycles associated with conveyor-on and conveyor-off phases have much larger amplitudes; furthermore, the strong iceberg calving events lead to a larger loss of ice sheet mass and hence the period of the oscillations is longer (several thousand years). This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

科氏力对河口分汊的影响   总被引：1，自引：0，他引：1       下载免费PDF全文

金元欢  沈焕庭 《海洋科学》1993,17(4):52-56

以长江口、黄河口、珠江口、闽江口等几个分汊河口为例,分析了科氏力在河口分汊中的作用。结果表明,涨落潮流路分歧主要通过形成涨落潮冲刷槽和中央缓流区浅滩而逐渐使河口产生分汊;水面横比降则以横向环流和横向切滩两种形式,或堆积或冲刷,导致河口分汊。  相似文献   

太平洋年代际海洋变率研究进展   总被引：10，自引：1，他引：10  

王东晓  谢强  刘赟  刘钦燕  杜岩 《热带海洋学报》2003,22(1):76-83

随着“气候变率与可预报性研究”（CLIVAR计划）的实施，年代际气候变率研究已经成为国际气候研究的一个新热点，由于海洋特别是海洋次表层具有巨大的热损性，海洋环流在年代际气候变率中所起的作用已得到越来越多的重视。但迄今为止，海洋以什么方式参与到年代际气候变化中，海洋次表层在年际和年代际时间尺度上起到什么作用这些与海洋环流有关的问题仍未得到解决，而这些问题的解决将有助于建立一种完备的年代际气候变化机制的理论，文章通过对近10a来国内外在该领域内研究进展的回顾，提出了一个关于太平洋年际变化（如ENSO循环）和年代际变化（如PDO循环）相互作用的猜想，为今后在国内开展相关研究提供了一些设想。  相似文献   

Third order contribution to the wave-making resistance of a ship at finite depth of water     

Shahjada Tarafder  Md 《Ocean Engineering》2007,34(1):32-44

This paper presents a potential based boundary element method for solving a nonlinear free surface flow problem for a ship moving with a uniform speed in finite depth of water. The free surface boundary condition is linearized by the systematic method of perturbation in terms of a small parameter up to third order. The surfaces are discretized into flat quadrilateral elements and the influence coefficients are calculated by Morino's analytical formula. Dawson's upstream finite difference operator is used in order to satisfy the radiation condition. The second order solution gives better result than the first or third order solution. So the present method with the second order solution can be adopted as a powerful tool for the hydrodynamic analysis of the thin ship in finite depth of water.  相似文献   

Steady Response of a Ventilated Thermocline to Enhanced Ekman Pumping     

Atsushi Kubokawa  Shang-Ping Xie 《Journal of Oceanography》2002,58(4):565-575

The steady response of the ventilated thermocline to an increase in Ekman pumping is investigated, focusing on the effect of the mixed layer depth distribution on the subsurface density anomaly. We consider only the subtropical gyre, and the mixed layer is assumed to be deep in the northwest and shallow elsewhere with a narrow transition zone separating the deep and shallow mixed layer regions. At the intersection of this narrow transition zone and the outcrop line, low potential vorticity fluid is subducted into and ventilates the thermocline. In such a situation, an enhancement of the Ekman pumping confined to the northern subtropical gyre leads to pronounced subsurface cold anomalies in the southern subtropics, which is free of anomalous forcing. These density anomalies are much greater than those that occur when either the mixed layer depth is zonally uniform or the Ekman pumping is enhanced in the whole subtropical gyre. They are caused by anomalous changes in the trajectory of the low potential vorticity fluid in response to anomalous Sverdrup flow. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

南海季风区地域性大气环流的结构     

周发琇  张涛  高荣珍 《中国海洋大学学报(自然科学版)》2001,31(4):467-472

作者使用 NCEP/ NCAR再分析资料 ,在热带 30°S～ 30°N纬带用谐波分析方法分离出超长波之后 ,再采用环流诊断方法 ,发现南海季风区存在地域性环流系统。文中给出冬、夏季风期该系统的三维空间结构和相应的热源分布 ,讨论了该地域性环流系统对南海季风气候及其异常的作用 ,并探讨夏季风爆发北部先于南部的一种可能的气候原因。  相似文献   

南海东北部表层沉积中有孔虫的分布及其环境意义   总被引：11，自引：0，他引：11  

徐建  黄宝琦  陈荣华  张富元 《热带海洋学报》2001,20(4):6-13

为了探讨南海东北部表层沉积中有孔虫分布的规律，选取184个表层样进行分析，结果发现有孔虫的垂向分布与碳酸盐的溶解作用密切相关。在2300－2500m水深以下，浮游有孔虫丰度迅速减小，而底栖有孔虫占有孔虫全群的比值BF／（BF＋PF）以及底栖有孔虫胶结质壳类的百分含量则迅速增加，这三者随水深的变化在3400－3500m处有一明显的转变，被认为是南海东北部CCD面（碳酸盐补偿深度）所在的位置，且该研究区内碳酸盐补偿深度南部较北部深100m。浮游有孔虫水平分布除了受表层海水温度的的控制外，黑潮南海分支以及吕宋岛北端上升流区带来的富营养水体的存在也起很重要的作用。  相似文献   

A Study on the Spectral Form of Nearshore Water Waves     

Kuo Yiyu Chien Chungching Professor 《中国海洋工程》1993,(3)

- The spectral form of wind waves is investigated based on the ocean wave data observed at three nearshore stations of Taiwan. In this study, the generalized forms of Pierson-Moskowitz spectrum and JONSWAP spectrum are used to describe the local wave spectrum by selecting suitable spectral form parameters. It is shown that, at a specific site, the similarity of wave spectral form exists. Thus it is possible to use a representative spectral form for a given nearshore region to describe the wave spectrum at this nearshore. On the other hand, the effects of relative water depth on spectral form are examined. The feasibility of two spectral models in finite water depth is evaluated by using the same field wave data.  相似文献   

2021年10月山西一次罕见持续性强降水过程物理机制分析     

乔钰  赵桂香  王妍 《沙漠与绿洲气象(新疆气象)》2024,18(2)

利用气象观测资料、NCEP/NCAR 1°×1°再分析资料以及GDAS资料,对2021年10月2-7日山西持续性强降水天气过程进行分析。结果表明：稳定的乌拉尔山低槽后部冷空气扩散,中纬度短波槽东移,与副热带高压外围西南暖湿气流持续交汇,同时高低空急流耦合形成强烈上升运动,低层切变线和地面辐合线稳定维持,及低层水汽不断输送并形成辐合,为持续性强降水的发生发展提供有利动力和水汽条件。此次强降水过程分为对流性降水和稳定性降水2个阶段,2阶段水汽输送通道的源地、路径、高度均有明显差异,但水汽输送贡献率均以对流层中低层山西南侧的水汽输送占主导地位。降水开始前,对流层中上层存在对称不稳定,大气可降水量明显跃增;对流性降水阶段,干空气不断入侵,对流不稳定快速建立与释放,对流层中低层水汽辐合区与强上升气流配合,导致山西出现强对流天气。地形的阻挡、抬升及地形收缩作用,对局地极端强降水具有增幅作用。  相似文献   

山东三山岛金矿床流体包裹体特征及其地质意义   总被引：5，自引：0，他引：5  

周国发  吕古贤  邓军  申玉科  郭涛 《现代地质》2008,22(1):24-33

三山岛金矿床位于莱州市三山岛—仓上断裂带内,矿石主要为蚀变岩和含金石英脉2种类型。随着胶东金矿床研究的深入和三山岛金矿资源的不断减少,对三山岛金矿床的成矿作用及深部开发前景问题研究具有更重要的意义。针对上述问题,对三山岛金矿床2种类型矿石的成矿流体特征进行对比研究,认为代表成矿早—中期的蚀变岩型矿石形成于中温(均一温度为325～240℃)、低盐度(2.07%～6.88%)、低密度(0.720～0.868g/cm3)、酸碱性不均匀(pH=3.27～10.43)、以氟化物和氯化物为成矿物质载体的还原性流体;代表成矿中—晚期的含金石英脉型矿石形成于中—低温(均一温度为306～160℃)、低盐度(1.05%～9.73%)、低密度(0.739～0.962g/cm3)、碱性(pH=9.25～9.85)、以氯化物和硫化物为成矿物质载体的还原性流体。成矿流体性质的转变反映了成矿流体处于由比较封闭到比较开放的构造环境的转变期,且成矿流体早期以原生岩浆水为主,后期有变质水、大气降水以及海水的参与作用。三山岛金矿成矿深度为2.5～5km,根据目前的开采深度推算其深部还有一定的资源量可供开发。  相似文献