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本文利用大洋环流模式POP研究RCP4.5情景下21世纪格陵兰冰川不同的融化速率对全球及区域海平面变化的影响。结果显示:当格陵兰冰川的融化速率以每年1%增加时,全球大部分海域的动力和比容海平面变化基本不变,主要是由于格陵兰冰川在低速融化时并不会导致大西洋经向翻转流减弱。当格陵兰冰川的融化速率以每年3%和每年7%增加时,动力海平面在北大西洋副极地、大西洋热带、南大西洋副热带和北冰洋海域呈现出显著的上升趋势,这是因为格陵兰冰川快速融化导致大量的淡水输入附近海域,造成该上层海洋层化加强和深对流减弱,导致大西洋经向翻转流显著减弱;与此同时,热比容海平面在北冰洋、格陵兰岛南部海域和大西洋副热带海域显著下降,而在热带大西洋和湾流海域明显上升;此时盐比容海平面的变化与热比容海平面是反相的,这是由于大量的低温低盐水的输入,造成北大西洋副极地海域变冷变淡、大西洋经向翻转流和热盐环流显著减弱,引起了太平洋向北冰洋的热通量和淡水通量减少,导致了北冰洋海水变冷变淡,同时热带大西洋滞留了更多的高温高盐水,随着湾流被带到北大西洋,北大西洋副极地海域低温低盐的海水,被风生环流输运到副热带海域。 相似文献
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从海洋动力学角度,概述了太平洋-印度洋贯穿流南海分支的主要入流和出流通道—吕宋海峡和卡里马塔海峡的研究现状。太平洋-印度洋贯穿流南海分支是太平洋、南海和印度尼西亚海域进行水体和热盐交换的传输带,对西太平洋、南海、印尼海和东印度洋的环流系统有重要影响。吕宋海峡水交换和卡里马塔海峡贯穿流都呈现冬季大夏季小的季节变化特征,对维持南海的物质、能量和动量平衡起重要作用。太平洋通过吕宋海峡向南海输运水体和热盐,并传递ENSO等气候信号,对南海的环流、水体和海洋环境都产生重要影响。卡里马塔海峡向印度尼西亚海区的水体和热盐输运对印度尼西亚贯穿流有重要意义。太平洋-印度洋贯穿流南海分支和印尼贯穿流的年际变化趋势呈反位相,两者相互调制相互影响,维持了太平洋-印度洋两大洋间的平衡关系,对全球大洋环流的结构和长期的气候变化有重要作用。 相似文献
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北太平洋经向翻转环流(NPMOC)是北太平洋所有经向翻转环流圈的总称,拥有5个环流圈结构.其中,热带环流圈(TC)、副热带环流圈(STC)和深层热带环流圈(DTC)位于北太平洋热带-副热带海域,是该海域间经向物质和能量交换的重要通道.主要运用NEMO模式对这3个经向翻转环流圈的年际变化特征和机理进行了研究.结果表明,TC、STC和DTC的经向流量都具有显著的年际变化特征:在El Nio期间,TC的南、北向流量均减弱,STC的北向流量增强、南向流量减弱,DTC的南向流量减弱;而在La Nia期间则相反.敏感性试验表明,在风应力强迫下得到的TC、STC南、北向流量和DTC南向流量的年际变化特征都很显著,并与在风应力、热通量和淡水通量共同强迫下得到的结果非常一致;而仅在热通量和淡水通量的强迫下,各分支流量的年际变化均较小.由此可见,风场驱动是引起北太平洋经向翻转环流年际变化的主要驱动因素,而热通量和淡水通量的影响却较小. 相似文献
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南印度洋绕极深层水的性质和空间分布以及南极绕极流的作用 总被引：1，自引：0，他引：1
利用世界大洋环流实验的南大洋观测温度、盐度和溶解氧资料,分析并说明了南印度洋绕极深层水的性质和空间分布特征,比较了30°E,90°E和145°E断面上温度、盐度和溶解氧的垂直分布及其异同,着重指出,在南印度洋的这3个不同经度断面上,绕极深层水和锋面的不同特征与南极绕极流越洋输运和南印度洋绕极深层水的经向运动有着密切的关系。实际上,绕极流的越洋输运是南大西洋与南印度洋之间以及南印度洋与南太平洋之间水交换的主要动力因素,对形成绕极深层水的物理性质的空间分布有着重要的作用。 相似文献
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北印度洋的经向热输送与热收支的季节与年际变化 总被引：3，自引：1，他引：3
探讨赤道以北印度洋的热量收支及变化机制。根据积分10年(1987～1996)的全球海洋模式(MOM 2 )资料,利用积分形式的热量平衡方程,系统地研究了北印度洋的经向热输送和热量收支的季节与年际变化。主要结论为:在季节尺度上,越赤道的经向热输送和赤道以北印度洋热含量变化有年循环特征,而海面净热通量呈现半年周期变化特点;在年际尺度上,热含量的变化主要由经向热输送的变化引起,其它项的影响较小;经向热输送集中在上5 0 0m ,尤其在15 0m以上;在总的经向热输送中,经向翻转环流的贡献起主要作用,涡动项的贡献比较小;某一纬度上经向热输送异常以及此纬度以北印度洋总的海面净热通量异常与此纬度上纬向积分的纬向风应力异常有很好的相关关系;还分析了10°N阿拉伯海和10°N孟加拉湾的经向热输送与越赤道的经向热输送的关系,以及海面净热通量各分量的变化特点。 相似文献
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南海南部与外海间的体积和热、盐输运及其对印尼贯穿流的贡献 总被引：11，自引：1，他引：11
根据中国近海高分辨率 ( 1 / 6°)环流模式的模拟结果 ,计算了南沙邻近海域与外海之间的海水体积、热量和盐量输运及其对印度尼西亚贯穿流的贡献。研究海域为 0°— 1 4°N的整个南海南部海域。计算得出 ,穿过研究海域流向印度尼西亚海域 ,最终流向印度洋的年平均体积、热量和盐量输运分别为 5 .2Sv( 1Sv =1× 1 0 6m3·s- 1 )、0 .5 7PW和 1 84Gg·s- 1 ,大约占印度尼西亚贯穿流相应输运量的 1 / 4。这一结果表明南海是全球大传送带这一全球海洋最主要热盐环流系统的重要通道之一。从南海流向印度尼西亚海域的通道以卡里马塔海峡为最主要 ,以下依次为巴拉巴克海峡、民都洛海峡和马六甲海峡。大的南向通量主要发生在冬、秋季 ,春末夏初总的通量向北。计算还得出输入本海区的热输运量比输出少 0 .0 64PW ,由这一结果推得 ,通过海 -气界面由大气进入海洋的年平均净热通量约为 30W·m- 2 。 相似文献
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北太平洋经向翻转环流是北太平洋所有经向翻转环流圈的总称,目前它拥有五个环流圈,即副热带环流圈(the subtropical cell,STC)、热带环流圈(the tropical cell,TC)、副极地环流圈(the subpolar cell,SPC)、深层热带环流圈(the deep tropical cell,DTC)和温跃层环流圈(the thermohaline cell,THC)。这些环流圈是北太平洋经向物质和能量交换的重要通道,它们的变化对海洋上层热盐结构和气候变化皆有重要影响。迄今,人们已对STC、TC和DTC的结构形态、变化特征与机理开展了广泛而深入的研究,并对STC的极向热输送特征也做了一些初步分析。但应指出的是,关于SPC和THC的研究仍较少,迄今尚不清楚这两个环流圈的三维结构和变异机理;而且,对北太平洋经向翻转环流的热盐输送研究尚处于起步阶段,目前对各环流圈的热盐输送特征、变化规律和变异机理仍知之甚少,这些科学问题亟待深入研究。 相似文献
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为了弄清北太平洋水入侵南海的状况,利用历史观测温-盐数据等资料对其进行了分析。结果表明:在盐度极大值层北太平洋水通过吕宋海峡的入侵整年发生,并且其入侵有很大的季节变化,冬季东北季风盛行时最强。北太平洋热带水(NPTW)入侵的季节变化与次表层地转流和南海的经向翻转环流结构有密切联系。具有盐度极小值特性的北太平洋中层水(NPIW)也通过吕宋海峡入侵南海,但其季节变化与NPTW完全反位相。冬季,由于在中层水深度北向运动的南海经向翻转环流的阻碍作用,NPIW入侵南海最弱。作者认为,北太平洋水入侵南海的机制可以基本上从南海的地转流及经向翻转环流得到解释。 相似文献
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基于该系列文章前文研究中构建的海气耦合气候模式和所揭示的北大西洋热盐环流年代际振荡机制,针对海气要素对该振荡机制的影响问题进行了重点的探讨。为细致准确的研究北大西洋海洋要素同北大西洋热盐环流年代际振荡的关系,有针对性的定义了副极地海区表层密度指数和北大西洋暖流强度指数并对模式结果进行了全面分析。分析结果表明副极地海区表层密度变化领先大西洋径向翻转环流(MOC)变化7 a,北大西洋暖流的变化领先 MOC变化4 a,格陵兰－苏格兰海脊溢流水强度(包括丹麦海峡溢流水和法鲁海峡溢流水,是北大西洋深层水的重要来源)的变化领先 MOC的变化3 a;北大西洋大气要素变化对北大西洋热盐环流年代际振荡有非常重要的调制作用,当副极地流环和北大西洋暖流(NAC)达到最强的2 a之前,高纬度地区大气为气旋式环流异常,中纬度地区大气为反气旋式环流异常,海表热通量在大西洋副极地海区是负异常,这都有利于副极地流环和NAC的加强,更多高盐度的北大西洋水进入格陵兰-冰岛-挪威海(GIN)海域,由此可以导致GIN海域表层密度上升,使水体的层结稳定性减弱,有利于深层对流的发生,同时大气变化通过风应力旋度和海表热通量也直接影响GIN海域深层水的生成,进而导致格陵兰－苏格兰海脊溢流水的强度增加。 相似文献
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The annual mean volume and heat transport sketches through the inter-basin passages and transoceanic sections have been constructed based on 1 400-year spin up results of the MOM4p1. The spin up starts from a state of rest, driven by the monthly climatological mean force from the NOAA World Ocean Atlas(1994). The volume transport sketch reveals the northward transport throughout the Pacific and southward transport at all latitudes in the Atlantic. The annual mean strength of the Pacific-Arctic-Atlantic through flow is 0.63×106 m3/s in the Bering Strait. The majority of the northward volume transport in the southern Pacific turns into the Indonesian through flow(ITF) and joins the Indian Ocean equatorial current, which subsequently flows out southward from the Mozambique Channel, with its majority superimposed on the Antarctic Circumpolar Current(ACC). This anti-cyclonic circulation around Australia has a strength of 11×106 m3/s according to the model-produced result. The atmospheric fresh water transport, known as P-E+R(precipitation minus evaporation plus runoff), constructs a complement to the horizontal volume transport of the ocean. The annual mean heat transport sketch exhibits a northward heat transport in the Atlantic and poleward heat transport in the global ocean. The surface heat flux acts as a complement to the horizontal heat transport of the ocean. The climatological volume transports describe the most important features through the inter-basin passages and in the associated basins, including: the positive P-E+R in the Arctic substantially strengthening the East Greenland Current in summer; semiannual variability of the volume transport in the Drake Passage and the southern Atlantic-Indian Ocean passage; and annual transport variability of the ITF intensifying in the boreal summer. The climatological heat transports show heat storage in July and heat deficit in January in the Arctic; heat storage in January and heat deficit in July in the Antarctic circumpolar current regime(ACCR); and intensified heat transport of the ITF in July. The volume transport of the ITF is synchronous with the volume transport through the southern Indo-Pacific sections, but the year-long southward heat transport of the ITF is out of phase with the heat transport through the equatorial Pacific, which is northward before May and southward after May. This clarifies the majority of the ITF originating from the southern Pacific Ocean. 相似文献
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利用50 a的SODA资料对1月(冬季)和7月(夏季)印度洋越赤道经向翻转环流的年际变化进行研究。通过对2类典型年份的合成分析指出:1月份正异常年对应的经向翻转环流偏强,向北的经向热输送增加;7月份正异常年对应的经向翻转环流则偏弱,向南的经向热输送减少;1月份和7月份的负异常年皆与其正异常年相反;越赤道经向翻转环流有明显的年际变化,平均周期在4 a左右;经向翻转环流的年际变化和海面风场的变化密切相关。提出了反映1月和7月此环流年际变化的几个指数。 相似文献
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Freshwater transport estimates and the global overturning circulation: Shallow, deep and throughflow components 总被引：2，自引：0，他引：2
Lynne D. Talley 《Progress in Oceanography》2008,78(4):257-303
Meridional ocean freshwater transports and convergences are calculated from absolute geostrophic velocities and Ekman transports. The freshwater transports are analyzed in terms of mass-balanced contributions from the shallow, ventilated circulation of the subtropical gyres, intermediate and deep water overturns, and Indonesian Throughflow and Bering Strait components. The following are the major conclusions:
- 1.
- Excess freshwater in high latitudes must be transported to the evaporative lower latitudes, as is well known. The calculations here show that the northern hemisphere transports most of its high latitude freshwater equatorward through North Atlantic Deep Water (NADW) formation (as in [Rahmstorf, S., 1996. On the freshwater forcing and transport of the Atlantic thermohaline circulation. Climate Dynamics 12, 799-811]), in which saline subtropical surface waters absorb the freshened Arctic and subpolar North Atlantic surface waters (0.45 ± 0.15 Sv for a 15 Sv overturn), plus a small contribution from the high latitude North Pacific through Bering Strait (0.06 ± 0.02 Sv). In the North Pacific, formation of 2.4 Sv of North Pacific Intermediate Water (NPIW) transports 0.07 ± 0.02 Sv of freshwater equatorward.In complete contrast, almost all of the 0.61 ± 0.13 Sv of freshwater gained in the Southern Ocean is transported equatorward in the upper ocean, in roughly equal magnitudes of about 0.2 Sv each in the three subtropical gyres, with a smaller contribution of <0.1 Sv from the Indonesian Throughflow loop through the Southern Ocean. The large Southern Ocean deep water formation (27 Sv) exports almost no freshwater (0.01 ± 0.03 Sv) or actually imports freshwater if deep overturns in each ocean are considered separately (−0.06 ± 0.04 Sv).This northern-southern hemisphere asymmetry is likely a consequence of the “Drake Passage” effect, which limits the southward transport of warm, saline surface waters into the Antarctic [Toggweiler, J.R., Samuels, B., 1995a. Effect of Drake Passage on the global thermohaline circulation. Deep-Sea Research I 42(4), 477-500]. The salinity contrast between the deep Atlantic, Pacific and Indian source waters and the denser new Antarctic waters is limited by their small temperature contrast, resulting in small freshwater transports. No such constraint applies to NADW formation, which draws on warm, saline subtropical surface waters .
- 2.
- The Atlantic/Arctic and Indian Oceans are net evaporative basins, hence import freshwater via ocean circulation. For the Atlantic/Arctic north of 32°S, freshwater import (0.28 ± 0.04 Sv) comes from the Pacific through Bering Strait (0.06 ± 0.02 Sv), from the Southern Ocean via the shallow gyre circulation (0.20 ± 0.02 Sv), and from three nearly canceling conversions to the NADW layer (0.02 ± 0.02 Sv): from saline Benguela Current surface water (−0.05 ± 0.01 Sv), fresh AAIW (0.06 ± 0.01 Sv) and fresh AABW/LCDW (0.01 ± 0.01 Sv). Thus, the NADW freshwater balance is nearly closed within the Atlantic/Arctic Ocean and the freshwater transport associated with export of NADW to the Southern Ocean is only a small component of the Atlantic freshwater budget.For the Indian Ocean north of 32°S, import of the required 0.37 ± 0.10 Sv of freshwater comes from the Pacific through the Indonesian Throughflow (0.23 ± 0.05 Sv) and the Southern Ocean via the shallow gyre circulation (0.18 ± 0.02 Sv), with a small export southward due to freshening of bottom waters as they upwell into deep and intermediate waters (−0.04 ± 0.03 Sv).The Pacific north of 28°S is essentially neutral with respect to freshwater, −0.04 ± 0.09 Sv. This is the nearly balancing sum of export to the Atlantic through Bering Strait (−0.07 ± 0.02 Sv), export to the Indian through the Indonesian Throughflow (−0.17 ± 0.05 Sv), a negligible export due to freshening of upwelled bottom waters (−0.03 ± 0.03 Sv), and import of 0.23 ± 0.04 Sv from the Southern Ocean via the shallow gyre circulation.
- 3.
- Bering Strait’ssmall freshwater transport of <0.1 Sv helps maintains the Atlantic-Pacific salinity difference. However, proportionally large variations in the small Bering Strait transport would only marginally impact NADW salinity, whose freshening relative to saline surface water is mainly due to air-sea/runoff fluxes in the subpolar North Atlantic and Arctic. In contrast, in the Pacific, because the total overturning rate is much smaller than in the Atlantic, Bering Strait freshwater export has proportionally much greater impact on North Pacific salinity balances, including NPIW salinity.
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The structure of the annual-mean shallow meridional overturning circulation(SMOC) in the South China Sea(SCS) and the related water movement are investigated,using simple ocean data assimilation(SODA) outputs.The distinct clockwise SMOC is present above 400 m in the SCS on the climatologically annual-mean scale,which consists of downwelling in the northern SCS,a southward subsurface branch supplying upwelling at around 10°N and a northward surface flow,with a strength of about 1×10~6 m~3/s.The formation mechanisms of its branches are studied separately.The zonal component of the annual-mean wind stress is predominantly westward and causes northward Ekman transport above 50 m.The annual-mean Ekman transport across 18°N is about 1.2×10~6 m~3/s.An annual-mean subduction rate is calculated by estimating the net volume flux entering the thermocline from the mixed layer in a Lagrangian framework.An annual subduction rate of about 0.66×10~6m~3/s is obtained between 17° and 20°N,of which 87% is due to vertical pumping and 13% is due to lateral induction.The subduction rate implies that the subdution contributes significantly to the downwelling branch.The pathways of traced parcels released at the base of the February mixed layer show that after subduction water moves southward to as far as 11°N within the western boundary current before returning northward.The velocity field at the base of mixed layer and a meridional velocity section in winter also confirm that the southward flow in the subsurface layer is mainly by strong western boundary currents.Significant upwelling mainly occurs off the Vietnam coast in the southern SCS.An upper bound for the annual-mean net upwelling rate between 10° and 15°N is 0.7×10~6m~3/s,of which a large portion is contributed by summer upwelling,with both the alongshore component of the southwest wind and its offshore increase causing great upwelling. 相似文献
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《Deep Sea Research Part I: Oceanographic Research Papers》2001,48(8):1821-1845
A reduced estimate of Agulhas Current transport provides the motivation to examine the sensitivity of Indian Ocean circulation and meridional heat transport to the strength of the western boundary current. The new transport estimate is 70 Sv, much smaller than the previous value of 85 Sv. Consideration of three case studies for a large, medium and small Agulhas Current transport demonstrate that the divergence of heat transport over the Indian Ocean north of 32°S has a sensitivity of 0.08 PW per 10 Sv of Agulhas transport, and freshwater convergence has a sensitivity of 0.03×109 kg s−1 per 10 Sv of transport. Moreover, a smaller Agulhas Current leads to a better silica balance and a smaller meridional overturning circulation for the Indian Ocean. The mean Agulhas Current transport estimated from time-series current meter measurements is used to constrain the geostrophic transport in the western boundary region in order to re-evaluate the circulation, heat and freshwater transports across 32°S. The Indonesian Throughflow is taken to be 12 Sv at an average temperature of 18°C. The constrained circulation exhibits a vertical–meridional circulation with a net northward flow below 2000 dbar of 10.1 Sv. The heat transport divergence is estimated to be 0.66 PW, the freshwater convergence to be 0.54×109 kg s−1, and the silica convergence to be 335 kmol s−1. Meridional transports are separated into barotropic, baroclinic and horizontal components, with each component conserving mass. The barotropic component is strongly dependent on the estimated size of the Indonesian Throughflow. Surprisingly, the baroclinic component depends principally on the large-scale density distribution and is nearly invariant to the size of the overturning circulation. The horizontal heat and freshwater flux components are strongly influenced by the size of the Agulhas Current because it is warmer and saltier than the mid-ocean. The horizontal fluxes of heat and salt penetrate down to 1500 m depth, suggesting that warm and salty Red Sea Water may be involved in converting the intermediate and upper deep waters which enter the Indian Ocean from the Southern Ocean into warmer and saltier waters before they exit in the Agulhas Current. 相似文献
18.
The three-dimensional structure and the seasonal variation of the North Pacific meridional overturning circulation (NPMOC) are analyzed based on the Simple Ocean Data Assimilation data and Argo profiling float data.The NPMOC displays a multi-cell structure with four cells in the North Pacific altogether.The TC and the STC are a strong clockwise meridional cell in the low latitude ocean and a weaker clockwise meridional cell between 7°N and 18°N,respectively, while the DTC and the subpolar cell are a weaker ... 相似文献