东海与邻近海域水、热、盐通量的季节变化研究

本文基于高分辨率的区域海洋数值模式对东海及邻近海域进行温、盐、流的数值模拟,模拟结果与实测结果拟合较好。结果表明:东海与邻近海域的水交换过程具有显著的季节变化特征。从流量的角度看,台湾海峡、台湾-西表岛之间水道和西表岛-冲绳岛之间水道是外海水流入东海的3个主要水道,而冲绳岛-奄美大岛、吐噶喇海峡、大隅海峡、济州岛东部和黄东海断面是海水流出东海的水道;其年平均体积输运值分别为1.06×106 m3/s、20.49×106 m3/s、3.20×106 m3/s、-0.92×106 m3/s、-20.59×106 m3/s、-0.30×106 m3/s、-2.37×106 m3/s和-0.37×106 m3/s（向内为正）。对比发现,东海与邻近海域之间各水道的体积、热量和盐量输运均具有相似的季节变化趋势,其最大值往往出现在夏季（7月或8月）,最小值往往出现在冬季（1月或2月）。从7月到11月整个东海是流量净流出的过程,而从12月到翌年6月是流量净流入的过程,全年流量基本上保持平衡状态。东海终年存在向黄海的净输入,其体积、热量和盐量的年平均输运值分别为0.37×106 m3/s,0.027×1015 W和12.7×106 kg/s。     

舟山渔场及其邻近海域水团的季节特征

根据2001年夏季和2002年冬季两次现场调查所收集的CTD和营养盐资料,利用模糊聚类分析法,对舟山渔场及其邻近海域水团的季节特征进行了分析.结果表明,舟山渔场及其邻近海域水团的配置、分布范围、温盐特性和营养盐含量都有明显的季节特征.其中,冬季在全海域共有3个水团(江浙沿岸水、台湾暖流表层水和黄海混合水),而夏季则存在4个水团(江浙沿岸水、台湾暖流表层水、台湾暖流深层水和黄海混合水);冬季,江浙沿岸水的分布范围较小,温度偏低,盐度略高,营养盐偏高,而夏季,其分布范围较大,温度偏高,盐度偏低,营养盐偏低;冬季,台湾暖流表层水北伸最强,厚度最厚,温度最低,盐度最高,硅酸盐和硝酸盐偏高,而夏季,则北伸最弱,厚度最薄,温度最高,盐度最低,硅酸盐和硝酸盐偏低;台湾暖流深层水是一个季节性水团,它含有较丰富的营养盐;黄海混合水的分布范围和营养盐含量也都呈现出明显的季节特征.     

南海等密度面环流季节变化的数值模拟研究

In this study, we develop a variable-grid global ocean general circulation model(OGCM) with a fine grid(1/6)°covering the area from 20°S–50°N and from 99°–150°E, and use the model to investigate the isopycnal surface circulation in the South China Sea(SCS). The simulated results show four layer structures in vertical: the surface and subsurface circulation of the SCS are characterized by the monsoon driven circulation, with basin-scaled cyclonic gyre in winter and anti-cyclonic gyre in summer. The intermediate layer circulation is opposite to the upper layer, showing anti-cyclonic gyre in winter but cyclonic gyre in summer. The circulation in the deep layer is much weaker in spring and summer, with the maximum velocity speed below 0.6 cm/s. In fall and winter, the SCS deep layer circulation shows strong east boundary current along the west coast of Philippine with the velocity speed at 1.5 m/s, which flows southward in fall and northward in winter. The results have also revealed a fourlayer vertical structure of water exchange through the Luzon Strait. The dynamics of the intermediate and deep circulation are attributed to the monsoon driving and the Luzon Strait transport forcing.     

Dynamics of water exchange and salt flux in the Macuse Estuary,central Mozambique,southern Africa

The Siberian subspecies of the red knot Calidris canutus canutus spends the non-breeding season largely in West Africa (Mauritania and Guinea Bissau), where approximately half a million occurred in the 1980s. It was a rarely seen in southern Africa in the early part of the 20th century, but there were about 12 500 in the 1970s and 1980s. The main sites were Langebaan Lagoon, Berg River Estuary, Olifants River Estuary (South Africa) and Walvis Bay Lagoon (Namibia). There was a decline in the number of red knots at Langebaan Lagoon in the 1990s, to around 20% of the number that occurred there in the 1980s. Numbers remained low in the 2000s. In addition, the percentage that remained during the austral winter (the breeding season in the Arctic) declined, and there was none during the period 2001–2009. This suggested that first-year birds, which largely comprise the austral winter population, were no longer travelling to southern Africa. The decline in numbers coincided with the decline in West Africa, but it was disproportionately larger in southern Africa. The observed pattern of change is consistent with a buffer effect, whereby southern Africa represents an extension to the range to less suitable habitat (requiring a 6 000 km extension to the migration) when the population size and competition is high in the main localities in West Africa. We are probably now witnessing the gradual decline in the number of adult birds who are fixed in their use of southern Africa as their non-breeding quarters.     

赤道印度洋中部断面东西水交换的季节变化及其区域差异

采用海洋再分析资料和实测资料研究了热带印度洋中部东西水交换特征。结果表明存在两个相互独立的过程,即北印度洋过程(4°~6°N)和赤道过程(2°S-2°N)。北印度洋过程受季风影响显著,11月至翌年3月冬季风期间表现出很强的低盐水向西输送,5-9月夏季风期间则为高盐水向东输送;由于冬季风期间的输送较强,年平均表现为低盐水向西输送。赤道过程分为表层过程和次表层过程。表层赤道过程受局地风场驱动,有明显的半年周期;4-5月和10-11月的东向流将赤道西印度洋的高盐水向东输送,其余月份相反;向东的输送较强,年平均表现为净高盐水向东输送。在次表层赤道过程没有明显的季节变化,海流全年一致向东,将海盆西部的高盐水向东输送。     

On the large-scale variability of the circulation and heat state of the ocean and atmosphere in the North Atlantic

A conclusion about two extreme regimes existing in the large-scale circulation in the North Atlantic has been drawn based on an analysis of the inter-annual variability of the analogue to the Rossby index, as well as that of the heat and dynamic characteristics in separate areas of the north subtropical circulation. The former is defined by a high level of circulation both in the atmosphere and in the subtropical water circulation. In the current century this regime was realized mainly in the years pertaining to the middle and end of a 22-year solar activity cycle (a 22-year cycle). The relatively low level of atmospheric circulation and the slackened water mass transport are typical of the second regime. It dominated mainly during the years relevant to the beginning and second half of a 22-year solar activity cycle.Translated by Mikhail M. Trufanov.     

安达曼海的热收支分析及其水交换研究

The characteristics of the T/S structures, water mass exchange and deep circulation in the Andaman Sea are investigated based on the simulation from a high-resolution general circulation model(MITgcm). The results show that, below 1 000 m, the water mass is saltier, warmer and more homogeneous in the Andaman Sea than that in the Bay of Bengal, attributing to the strong vertical mixing at the depth of ～1 800 m. The water mass exchange between the Andaman Sea and the Bay of Bengal goes through three major channels, which manifests itself as follows: the northern channel(Preparis Channel) is the main passage of water mass transport from the Bay of Bengal to the Andaman Sea, whereas the Middle Channel(the south of Andaman Islands and the north of Nicobar Islands) has an opposite transport; the southern channel(Great Channel) features with a four-layer water exchange which results in the least net transport among the three channels; all the transports through the three channels have an intra-annual variation with a period of half a year. At 1 000-m depth, the entire Andaman Sea is occupied by a cyclonic circulation in January and July while by an anticyclonic one in April and October. The semiannual cycle found in both the deep circulation and water mass exchange is likely associated with the downwelling eastward-propagating Kelvin waves induced by the semiannual westerly component in the equatorial Indian Ocean during intermonsoon seasons.     

Nonlinear dynamics of the circulation variability in the western ocean

The nonlinear dynamics of the low-frequency variability of a mid-latitude ocean are studied. The mechanism of the separation of the western boundary current from the western wall, as well as the meridional displacements of the separation point and the separated eastward jet, is analyzed. A regional barotropic quasigeostrophic eddy-resolving numerical model is used for the analysis. The flow in a rectangular domain is simulated by the constant inflow and outflow of fluid through the boundaries. A regime when the nonlinearity prevails over the dissipation and the advection and β terms are of the same order of magnitude is considered, which is characteristic of the actual ocean. When the nonlinearity exceeds the threshold value, a periodic solution is obtained. The solution is determined by the nonslip boundary condition at the western wall. The solution obtained is studied in detail. The meridional displacements of the western boundary current separation point with respect to the western wall and the separated eastward jet can reach a few hundred kilometers. Their intensities and the intensity of the recirculation gyre in the western boundary current are found to oscillate with a period of about five years.     

北冰洋与邻近海区海洋-海冰模式的试算与校验

本文将目前先进的大尺度海洋、海冰模式(NEMO3.6和LIM3)应用于北大西洋–北冰洋–北太平洋(简称NAPA),并进行了试验后报模拟。所建立的模式NAPA1/4和NAPA1/12的水平分辨率分别为(1/4)°和(1/12)°经、纬度,计算范围覆盖太平洋45°N以北海区、整个北冰洋及北大西洋;其中,NAPA1/4和NAPA1/12在北大西洋的边界分别为26°N和7°N。目前,已利用NAPA1/4完成了1993–2015年的后报模拟。本文基于观测数据和已发表文献对模拟结果中的北冰洋海冰变化、环流结构以及水文特征进行了校验。结果表明,NAPA1/4能够再现北冰洋的主要热力与动力过程,可以用来分析海冰、水团、大西洋/太平洋入/出流等的季节与年际变化规律。利用NAPA1/12进行了1993–1996年的模拟计算。初步结果分析表明,提高分辨率可更为精细地刻画北冰洋的海冰、水团和环流的结构。     

Seasonal cycle of circulation in the Antarctic Peninsula and the off-shelf transport of shelf waters into southern Drake Passage and Scotia Sea

The seasonal cycle of circulation and transport in the Antarctic Peninsula shelf region is investigated using a high-resolution (∼2 km) regional model based on the Regional Oceanic Modeling System (ROMS). The model also includes a naturally occurring tracer with a strong source over the shelf (radium isotope ²²⁸Ra, t_1/2=5.8 years) to investigate the sediment Fe input and its transport. The model is spun-up for three years using climatological boundary and surface forcing and then run for the 2004–2006 period using realistic forcing. Model results suggest a persistent and coherent circulation system throughout the year consisting of several major components that converge water masses from various sources toward Elephant Island. These currents are largely in geostrophic balance, driven by surface winds, topographic steering, and large-scale forcing. Strong off-shelf transport of the Fe-rich shelf waters takes place over the northeastern shelf/slope of Elephant Island, driven by a combination of topographic steering, extension of shelf currents, and strong horizontal mixing between the ACC and shelf waters. These results are generally consistent with recent and historical observational studies. Both the shelf circulation and off-shelf transport show a significant seasonality, mainly due to the seasonal changes of surface winds and large-scale circulation. Modeled and observed distributions of ²²⁸Ra suggest that a majority of Fe-rich upper layer waters exported off-shelf around Elephant Island are carried by the shelfbreak current and the Bransfield Strait Current from the shallow sills between Gerlache Strait and Livingston Island, and northern shelf of the South Shetland Islands, where strong winter mixing supplies much of the sediment derived nutrients (including Fe) input to the surface layer.     

Seasonal variations of the ocean surface circulation in the vicinity of Palau

The surface circulation in the western equatorial Pacific Ocean is investigated with the aim of describing intra-annual variations near Palau (134°30′ E, 7°30′ N). In situ data and model output from the Ocean Surface Currents Analysis—Real-time, TRIangle Trans-Ocean buoy Network, Naval Research Laboratory Layered Ocean Model and the Joint Archive for Shipboard ADCP are examined and compared. Known major currents and eddies of the western equatorial Pacific are observed and discussed, and previously undocumented features are identified and named (Palau Eddy, Caroline Eddy, Micronesian Eddy). The circulation at Palau follows a seasonal variation aligned with that of the Asian monsoon (December–April; July–October) and is driven by the major circulation features. From December to April, currents around Palau are generally directed northward with speeds of approximately 20 cm/s, influenced by the North Equatorial Counter-Current and the Mindanao Eddy. The current direction turns slightly clockwise through this boreal winter period, due to the northern migration of the Mindanao Eddy. During April–May, the current west of Palau is reduced to 15 cm/s as the Mindanao Eddy weakens. East of Palau, a cyclonic eddy (Palau Eddy) forms producing southward flow of around 25 cm/s. The flow during the period July to September is disordered with no influence from major circulation features. The current is generally northward west of Palau and southward to the east, each with speeds on the order of 5 cm/s. During October, as the Palau Eddy reforms, the southward current to the east of Palau increases to 15 cm/s. During November, the circulation transitions to the north-directed winter regime.     

印度洋海底压强的季节和长期变化

利用2003—2015年的重力恢复和气候实验(Gravity Recovery and Climate Experiment, GRACE)卫星观测数据, 揭示了印度洋海底压强的变化特征, 并探讨了其变化机制。结果表明, 印度洋海底压强具有显著的季节变化特征, 北半球冬季在40°S以北(南), 海底压强呈负(正)异常, 夏季分布与冬季相反。印度洋区域的海底压强空间分布与Ekman输送空间分布有较好的对应关系。正压涡度方程诊断结果表明, 利用风场重构的海底压强能够较好地解释印度洋海底压强的季节和长期变化。此外, 海平面变化收支分析表明, 海底压强的变化在高纬度区域主导了海平面变化。     

Eddy-resolving ocean circulation in the Asian-Australian region inferred from an ocean reanalysis effort

The first global ocean reanalysis with focus on the Asian-Australian region was performed for the period October 1992 to June 2006. The 14-year experiment assimilated available observations of altimetric sea-level anomaly, satellite SST and quality-controlled in situ temperature and salinity profiles from a range of sources, including field surveys and the Argo float array. This study focuses on dominant circulation patterns in the South-East Asian/Australian region as simulated by an eddy-resolving and data-assimilating ocean general circulation model. New estimates of the ocean circulation are provided which are largely in agreement with the limited number of observations. Transports of key currents in the region are as follows: The total (top-to-bottom) annual mean Indonesian Throughflow transport and its standard deviation are 9.7 ± 4.4 Sv from the Pacific to the Indian Ocean with a minimum in January (6.6 Sv) and a maximum in April (12.3 Sv). The Leeuwin Current along the west coast of Australia is dominated by eddy structures with a mean southward transport of 4.1 ± 2.0 Sv at 34°S. Along the southern coast of Australia a narrow shelf edge current known as the South Australian Current advects 4.5 ± 2.6 Sv eastward at 130°E. The South Australian Current converges east of Tasmania with the eddy-rich extension of East Australian Current. At 32°S this current transports 36.8 ± 18.5 Sv southward. A dominating feature of the circulation between north-eastern Australia and Papua-New Guinea is the strong and quasi-permanent Coral Sea Gyre. This gyre is associated with the highly variable Hiri Current which runs along the south coast of Papua-New Guinea and advects 8.2 ± 19.1 Sv into the Western Pacific Ocean. All of these transport estimates are subject to strong eddy variability.     

世界大洋中绝热运动导致的纬向翻转环流和纬向热输送

Zonal overturning circulation(ZOC) and its associated zonal heat flux(ZHF) are important components of the oceanic circulation and climate system, although these conceptions have not received adequate attentions.Heaving induced by inter-annual and decadal wind stress perturbations can give rise to anomalous ZOC and ZHF.Based on a simple reduced gravity model, the anomalous ZOC and ZHF induced by idealized heaving modes in the world oceans are studied. For example, in a Pacific-like model basin intensified equatorial easterly on decadal time scales can lead to a negative ZOC with a non-negligible magnitude(–0.3×106 m3/s) and a considerable westward ZHF with an amplitude of –11.2 TW. Thus, anomalous ZOC and ZHF may consist of a major part of climate signals on decadal time scales and thus play an important role in the oceanic circulation and climate change.     

Antarctic Intermediate Water variability in the northern New Zealand region

In the region between 30°S and northern New Zealand, vertical salinity profiles through the core of the Antarctic Intermediate Water (AAIW) show a high degree of spatial and temporal variability, and this variability is much larger than that found in nearby ocean areas. Characteristic features are interleaving of salinity layers and large changes in the salinity minimum between adjacent stations. Quantifying the changes through the calculation of an intrusion index highlights the degree of variability and the importance of boundary mixing along the New Zealand slope. However, the main cause of the variability is the meeting and mixing of higher salinity AAIW, arriving from the north‐west (having travelled around the subtropical gyre) with lower salinity AAIW arriving by more direct entry from the north‐east. These waters meet in the region through the action of the meso‐scale eddy field. Present data indicate that where strong salinity interleaving occurs, the length scales are of the order of 10 km and the time scales are of the order of a few days. Resolution of the processes at work will require studies on finer scales than presently available.     

Non-uniqueness of the ocean thermohaline circulation,discontinuous auto-oscillations,and internal variability of the climatic system

Stable and unstable stationary thermohaline circulations provided by a box model comprising three ventilated masses—surface, intermediate, and deep—are discussed. The most likely states have been determined. It is shown that jump-like variations of the thermocline circulation are likely. An inference is made that long-term (10 000 years) climatic oscillations may be caused by the internal variability of the climatic system rather than by astronomical factors.     

西太平洋暖池海域上层海洋热盐含量初步研究

基于2001年1月～2014年7月期间的Argo温盐剖面资料,利用循环平稳经验正交函数（CSEOF）分解、最大熵谱分析和相关分析等方法,研究了西太平洋暖池海域上层海洋热盐含量的空间分布、季节和年际变化特征,并探讨了其影响机制。结果表明,暖池海域近表层与次表层热含量逐年变化呈反位相变化模态,同样盐含量变化趋势也不尽相同。无论热含量还是盐含量,都存在着明显的季节和年际变化。CSEOF分析表明,暖池海域热含量第一模态空间场具有显著的东—西反相位年际振荡,盐含量第一模态则呈正-负-正的三极子模态,但时间序列显示,热含量在2007年以后经过3次位相调整,而盐含量2007年以后只经过一次位相调整,且这种年际变化都与ENSO事件有关,且热含量相比于盐含量受ENSO影响更大。El Niño期间,暖池海域西部热含量减少, 东部增加,La Niña期间则相反;研究海域南北部盐含量在El Niño期间增加,中部（暖池高温中心）减少,La Niña期间则相反;进一步分析表明,热含量变化主要受到局地风场以及纬向流的影响,而盐含量变化则受淡水通量和纬向流的影响。     

菲律宾海盆深层温盐结构与环流变化特征研究

基于ECCO2 (Estimating the Circulation and Climate of the Ocean)、 GLORYS12V1 (Global Ocean Reanalysis and Simulations)、ORA-S5 (Ocean ReAnalysis)三种海洋再分析数据,对比研究了菲律宾海盆深层温盐及环流的季节和年际变化特征。结果表明:三种数据显示的海盆深层温盐季节变化特征基本一致,在3 000～4 000 m水深区域,海水呈春夏两季高温低盐而秋冬季低温高盐特性,4 000 m以下海水温盐季节变化很小;沿西边界,温度与内部有明显差异且季节变化幅度相对较大。沿西边界的输运季节变化特征表现为10月至次年4月输运向南,5—9月输运向北,并且在8月份达最大值;表明存在沿西边界的流动,即菲律宾海盆与南端西卡罗林海盆(West Caroline Basin)之间存在季节性水体交换。海盆深层海水温盐年际变化也十分显著,但不同数据显示的变化特征存在较大差异。EOF和相关分析显示,三种再分析数据的深层位温与ENSO均存在一定相关性,ECCO2的深层位温变化与ENSO的相关性最强。由于长期观测数据较少,再分析数据的结果难以验证,因此目前对年际变化特征的研究仍具有很大的不确定性。     

Seasonal variability of the Antarctic Coastal Current and its driving mechanisms in the Weddell Sea

Insight into the dynamics of the Antarctic Coastal Current (ACoC) is achieved by quantifying the contributions of its driving mechanisms to the seasonal variability of its barotropic and baroclinic components. These mechanisms are sought out in the local wind, the sea-ice concentration, wind curl of the Weddell Gyre (Sverdrup transport) and the thermohaline forcing related to warming/cooling and ice melting and freezing. These driving mechanisms induce most of the seasonal variability of both the barotropic and baroclinic components of the ACoC by deepening the pycnocline towards the coast and sharpening the baroclinic profile following thermal wind balance. The resulting coastal current has mainly a barotropic transport (82%) and a major annual cycle, which explains 37% of this component's variability (tides and other high-frequency events generate 40%). The wind contributes with 58% of the seasonal variability of the barotropic component and 23% of the baroclinic; the sea-ice concentration contributes with 8% and 18%, respectively; Sverdrup transport with 4% and 30% and the thermohaline forcing with 30% and 29%. The results of this study are obtained with analysis of fifteen CTD sections (potential density and geostrophic velocities) of RV-Polarstern obtained between 1992 and 2005, as well as composite, spectral and harmonic analyses of 9 years of time series from moored instruments (current speed and temperature), wind speed, atmospheric pressure and sea-ice concentration of satellite imagery.