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1.
This study, using laboratory experiments and scaling analysis, evaluates the influence of geothermal heating on global oceanic circulation. Upon a well-developed large-scale convective flow, an additional heat flux perturbation δF/F is employed. The increments of flow and thermal properties, including eddy diffusivity KT, flow velocity V and bottom temperature Tb, are found to be independent of the applied heat flux F. Together with the scaling analysis of convective flow at different configurations, where the flow is thermally driven in the relatively low or extremely high turbulent thermal convections or the horizontal convection, the variances of flow properties, δKT/KT and δV/V, are found to be close to 0.5% and 0.75% at δF/F=2%. This means that the small heat flux perturbation plays a negligible role in the global convective flow. However, δTb/ΔT is found to be 1.5% at δF/F=2%, which would have a significant effect in the local region. The results might provide a clue to understanding the influence of geothermal heating on global oceanic circulation. It is expected that geothermal heating will contribute less than 1% in turbulent mixing and volume flux to global oceanic circulation, so its influence can be negligible in this situation. However, when it comes to the local environment, the influence of geothermal heating cannot be ignored. For example, temperature increases of about 0.5°C with geothermal heating would have a significant effect on the physical environments within the benthic boundary layer.  相似文献   

2.
Based on hydrographic data obtained at an ice camp deployed in the Makarov Basin by the 4th Chinese Arctic Research Expedition in August of 2010, temporal variability of vertical heat flux in the upper ocean of the Makarov Basin is investigated together with its impacts on sea ice melt and evolution of heat content in the remnant of winter mixed layer(r WML). The upper ocean of the Makarov Basin under sea ice is vertically stratified. Oceanic heat flux from mixed layer(ML) to ice evolves in three stages as a response to air temperature changes, fluctuating from 12.4 W/m2 to the maximum 43.6 W/m2. The heat transferred upward from ML can support(0.7±0.3) cm/d ice melt rate on average, and daily variability of melt rate agrees well with the observed results. Downward heat flux from ML across the base of ML is much less, only 0.87 W/m2, due to enhanced stratification in the seasonal halocline under ML caused by sea ice melt, indicating that increasing solar heat entering summer ML is mainly used to melt sea ice, with a small proportion transferred downward and stored in the r WML. Heat flux from ML into r WML changes in two phases caused by abrupt air cooling with a day lag. Meanwhile, upward heat flux from Atlantic water(AW) across the base of r WML, even though obstructed by the cold halocline layer(CHL), reaches0.18 W/m2 on average with no obvious changing pattern and is also trapped by the r WML. Upward heat flux from deep AW is higher than generally supposed value near 0, as the existence of r WML enlarges the temperature gradient between surface water and CHL. Acting as a reservoir of heat transferred from both ML and AW, the increasing heat content of r WML can delay the onset of sea ice freezing.  相似文献   

3.
The mean seasonal variability of turbulent heat fluxes in the tropical Atlantic Ocean is examined using the Woods Hole Oceanographic Institution(WHOI) flux product.The most turbulent heat fluxes occur during winter seasons in the two hemispheres,whose centers are located at 10°~20°N and 5°～15°S respectively.In climatological ITCZ,the turbulent heat fluxes are the greatest from June to August,and in equatorial cold tongue the turbulent heat fluxes are the greatest from March to May.Seasonal variability of sensible heat flux is smaller than that of latent heat flux and mainly is dominated by the variations of air-sea temperature difference.In the region with larger climatological mean wind speed(air-sea humidity difference),the variations of air-sea humidity difference(wind speed) dominate the variability of latent heat flux.The characteristics of turbulent heat flux yielded from theory analysis and WHOI dataset is consistent in physics which turns out that WHOI's flux data are pretty reliable in the tropical Atlantic Ocean.  相似文献   

4.
The experiment system of 1000 m deep sea mining system is built up with the similarity theory.Sine mechanism is used to simulate mining ship to generate lateral shock excitation by ocean wave.Simulation and experiment of spherical joint connecting deep sea mining system has been done in band six marine conditions.The results indicate that the moment of spherical joint connecting deep sea mining is smaller than that of the thread connected ones,the lifting pipe of spherical joint is "flexible pipe".The flexural torque of the articulated lifting pipe system in pump and buffer is generally periodic variation with some irregularity,the value is stable on 60 N·S,and it is obviously smaller than that of the fixed lifting pipe system;The total displacement exhibits cyclic variation pattern,and the periodicity of them is longer than that of sea current.The results of experiment and simulation are basically consistent.And the analysis in the paper offers theoretical foundation of 1000 m deep sea mining system in China.  相似文献   

5.
琼东南盆地深水区构造热演化特征及其影响因素分析   总被引：5，自引：1，他引：4  
To reveal the tectonic thermal evolution and influence factors on the present heat flow distribution, based on 154 heat flow data, the present heat flow distribution features of the main tectonic units are first analyzed in detail, then the tectonic thermal evolution histories of 20 profiles are reestablished crossing the main deep-water sags with a structural, thermal and sedimentary coupled numerical model. On the basis of the present geothermal features, the Qiongdongnan Basin could be divided into three regions: the northern shelf and upper slope region with a heat flow of 50–70 m W/m2, most of the central depression zone of 70–85 m W/m2, and a NE trending high heat flow zone of 85–105 m W/m2 lying in the eastern basin. Numerical modeling shows that during the syn-rift phase, the heat flow increases generally with time, and is higher in basement high area than in its adjacent sags. At the end of the syn-rift phase, the heat flow in the deepwater sags was in a range of 60–85 m W/m2, while in the basement high area, it was in a range of 75–100 m W/m2. During the post-rift phase, the heat flow decreased gradually, and tended to be more uniform in the basement highs and sags. However, an extensive magmatism, which equivalently happened at around 5 Ma, has greatly increased the heat flow values, and the relict heat still contributes about 10–25 m W/m2 to the present surface heat flow in the central depression zone and the southern uplift zone. Further analyses suggested that the present high heat flow in the deep-water Qiongdongnan Basin is a combined result of the thermal anomaly in the upper mantle, highly thinning of the lithosphere, and the recent extensive magmatism. Other secondary factors might have affected the heat flow distribution features in some local regions. These factors include basement and seafloor topography, sediment heat generation, thermal blanketing, local magmatic injecting and hydrothermal activities related to faulting and overpressure.  相似文献   

6.
1972-2013年北欧海深层水增暖   总被引：2，自引：1，他引：1  
The warming of deep waters in the Nordic seas is identified based on observations during Chinese 5th Arctic Expedition in 2012 and historical hydrographic data. The most obvious and earliest warming occurrs in the Greenland Basin(GB) and shows a coincident accelerated trend between depths 2 000 and 3 500 m. The observations at a depth of 3 000 m in the GB reveal that the potential temperature had increased from-1.30°C in the early 1970 s to-0.93°C in 2013, with an increase of about 0.37°C(the maximum spatial deviation is 0.06°C) in the past more than 40 years. This remarkable change results in that deep waters in the center of the Lofton Basin(LB) has been colder than that in the GB since the year 2007. As for the Norwegian Basin(NB), only a slight trend of warming have been shown at a depth around 2 000 m since the early 1980 s, and the warming amplitude at deeper waters is just slightly above the maximum spatial deviation, implying no obvious trend of warming near the bottom. The water exchange rate of the Greenland Basin is estimated to be 86% for the period from 1982 to 2013, meaning that the residence time of the Greenland Sea deep water(GSDW) is about 35 years. As the weakening of deep-reaching convection is going on, the abyssal Nordic seas are playing a role of heat reservoir in the subarctic region and this may cause a positive feedback on the deep-sea warming in both the Arctic Ocean and the Nordic seas.  相似文献   

7.
引潮力对海洋环流模式的影响   总被引：2，自引：1，他引：1  
The eight main tidal constituents have been implemented in the global ocean general circulation model with approximate 1° horizontal resolution.Compared with the observation data,the patterns of the tidal amplitudes and phases had been simulated fairly well.The responses of mean circulation,temperature and salinity are further investigated in the global sense.When implementing the tidal forcing,wind-driven circulations are reduced,especially those in coastal regions.It is also found that the upper cell transport of the Atlantic meridional overturning circulation(AMOC) reduces significantly,while its deep cell transport is slightly enhanced from 9×106m3/s to 10×106 m3/s.The changes of circulations are all related to the increase of a bottom friction and a vertical viscosity due to the tidal forcing.The temperature and salinity of the model are also significantly affected by the tidal forcing through the enhanced bottom friction,mixing and the changes in mean circulation.The largest changes occur in the coastal regions,where the water is cooled and freshened.In the open ocean,the changes are divided into three layers:cooled and freshened on the surface and below 3 000 m,and warmed and salted in the middle in the open ocean.In the upper two layers,the changes are mainly caused by the enhanced mixing,as warm and salty water sinks and cold and fresh water rises;whereas in the deep layer,the enhancement of the deep overturning circulation accounts for the cold and fresh changes in the deep ocean.  相似文献   

8.
The seasonal variation of mixing layer depth(MLD) in the ocean is determined by a wind stress and a buoyance flux.A South China Sea(SCS) ocean data assimilation system is used to analyze the seasonal cycle of its MLD.It is found that the variability of MLD in the SCS is shallow in summer and deep in winter,as is the case in general.Owing to local atmosphere forcing and ocean dynamics,the seasonal variability shows a regional characteristic in the SCS.In the northern SCS,the MLD is shallow in summer and deep in winter,affected coherently by the wind stress and the buoyance flux.The variation of MLD in the west is close to that in the central SCS,influenced by the advection of strong western boundary currents.The eastern SCS presents an annual cycle,which is deep in summer and shallow in winter,primarily impacted by a heat flux on the air-sea interface.So regional characteristic needs to be cared in the analysis about the MLD of SCS.  相似文献   

9.
Heat oscillation in the upper ocean of the southern South China Sea   总被引：3，自引：0，他引：3  
Data used in this study are temperature/depth profiles taken over the upper 400 m of the ocean in the southern South China Sea (4°-14° N, 106°-120° E) for the period 1961-1973. The data are analyzed on the grid 2 (latitude) by 2 (longitude) in space and bimonthly in time. The vertically averaged temperature (TAV) over the upper 100 m of the ocean is calculated as the estimate of the heat content in the upper ocean.The TAV is cooler in the northwest region of the study area and warmer in the southeast in the annual and seasonal mean figures. The first EOF (Empirical Orthogonal Function) of anomalous TAV accounts for 41 % of the total variance for the period 1961-1973. The time function associated with it displays a significant interannual changes in the heat content, with 2-4 a oscillation period and associated with the ENSO events. During ENSO event TAV increases with the tendency of increasing towards equator along the basin. This anomalous states also exist in the water layers below 100 m depth. T  相似文献   

10.
Synoptic features in/around thermal fronts and cross-frontal heat fluxes in the southern Huanghai./Yellow Sea and East China Sea （HES） were examined using the data collected from four airborne expendable bathythermograph surveys with horizontal approxmately 35 km and vertical 1 m（from the surface to 400 m deep） spacings. Since the fronts are strongly affected by HES current system, the synoptic thermal features in/around them represent the interaction of currents with surrounding water masses. These features can not be obtained from climatological data. The identified thermal features are listed as follows ： （ 1 ） multiple boundaries of cold water, asymmetric thermocline intrusion, locally-split front by homogeneous water of approxmately 18 ℃, and mergence of the front by the Taiwan Warm Current in/around summertime southern Cheju - Changjiang/Yangtze front and Tsushima front; （2） springtime frontal eddy-like feature around Tsushima front; （3） year-round cyclonic meandering and summertime temperature-inversion at the bottom of the surface mixed layer in Cheju - Tsushima front; and （4） multistructure of Kuroshio front. In the Kuroshio front the mean variance of vertical temperature gradient is an order of degree smaller than that in other HES fronts. The southern Cheju- Changjiang front and Cheju -Tsushima front are connected with each other in the summer with comparable cross-frontal temperature gradient. However, cross-frontal heat flux and lateral eddy diffusivity are stronger in the southern Cheju - Changjiang front. The cross-frontal heat exchange is the largest in the mixing zone between the modified Huanghai Sea bottom cold water and the Tsushima Warm Current, which is attributable to enhanced thermocline intrusions.  相似文献   

11.
Below the sill depth (at about 2400 m) of the Alpha-Mendeleyev ridge complex, the waters of the Canada Basin (CB) of the Arctic Ocean are isolated, with a 14C isolation age of about 500 yr. The potential temperature θ decreases with depth to a minimum θm≈−0.524°C near 2400 m, increases with depth through an approximately 300 m thick transition layer to θh≈−0.514°C, and then remains uniform from about 2700 m to the bottom at 3200–4000 m. The salinity increases monotonically with depth through the deep θm and transition layer from about 34.952 to about 34.956 and then remains uniform in the bottom layer. A striking staircase structure, suggestive of double-diffusive convection, is observed within the transition layer. The staircase structure is observed for about 1000 km across the basin and has been persistent for more than a decade. It is characterized by 2–3 mixed layers (10–60 m thick) separated by 2–16 m thick interfaces. Standard formulae, based on temperature and salinity jumps, suggest a double-diffusive heat flux through the staircase of about 40 mW m−2, consistent with the measured geothermal heat flux of 40–60 mW m−2. This is to be expected for a scenario with no deep-water renewal at present as we also show that changes in the bottom layer are too small to account for more than a small fraction of the geothermal heat flux. On the other hand, the observed interfaces between mixed layers in the staircase are too thick to support the required double-diffusive heat flux, either by molecular conduction or by turbulent mixing, as there is no evidence of sufficiently vigorous overturns within the interfaces. It therefore seems, that while the staircase structure may be maintained by a very weak heat flux, most of the geothermal heat flux is escaping through regions of the basin near lateral boundaries, where the staircase structure is not observed. The vertical eddy diffusivity required in these near-boundary regions is O(10−3) m2 s−1. This implies Thorpe scales of order 10 m. We observe what may be Thorpe scales of this magnitude in boundary-region potential temperature profiles, but cannot tell if they are compensated by salinity. The weak stratification of the transition layer means that the large vertical mixing rate implies a local dissipation rate of only O(10−10) W kg−1, which is not ruled out by plausible energy budgets. In addition, we discuss an alternative scenario of slow, continuous renewal of the CB deep water. In this scenario, we find that some of the geothermal heat flux is required to heat the new water and vertical fluxes through the transition layer are reduced.  相似文献   

12.
Hydrographic observations from four separate expeditions to the Eurasian Basin of the Arctic Ocean between 1991 and 2001 show a 300–700 m thick homogenous bottom layer. The layer is characterized by slightly warmer temperature compared to ambient, overlying water masses, with a mean layer thickness of 500±100 m and a temperature surplus of 7.0±2×10−3 °C. The layer is present in the deep central parts of the Nansen and Amundsen Basins away from continental slopes and ocean ridges and is spatially coherent across the interior parts of the deep basins. Here we show that the layer is most likely formed by convection induced by geothermal heat supplied from Earth's interior. Data from 1991 to 1996 indicate that the layer was in a quasi steady state where the geothermal heat supply was balanced by heat exchange with a colder boundary. After 1996 there is evidence of a reformation of the layer in the Amundsen Basin after a water exchange. Simple numerical calculations show that it is possible to generate a layer similar to the one observed in 2001 in 4–5 years, starting from initial profiles with no warm homogeneous bottom layer. Limited hydrographic observations from 2001 indicate that the entire deep-water column in the Amundsen Basin is warmer compared to earlier years. We argue that this is due to a major deep-water renewal that occurred between 1996 and 2001.  相似文献   

13.
加拿大海盆东南部锚定观测双扩散阶梯的时间演化研究   总被引：1，自引：1，他引：0  
加拿大海盆上层,分布着高温高盐的大西洋水和相对低温低盐的盐跃层下部水,两水团之间形成一系列的双扩散阶梯。通过分析2005年8月-2011年8月期间的锚定潜标数据,对双扩散阶梯和这两种水团之间的相互作用进行研究。基于固定盐度范围的方法,在盐度廓线中识别阶梯结构,在盐度34.45~34.83范围内,获取18个阶梯结构,并研究阶梯的参数。发现双扩散阶梯的位温主要受与其接近的水团的影响,同时也受其相邻的阶梯生成或消亡的影响,大西洋水对其上方的双扩散阶梯和盐跃层下部水起到加热作用;而盐跃层下部水的深度变化主导着大西洋水和双扩散阶梯的深度变化。两个相邻的阶梯具有一致的位温和深度变化趋势。通过经验公式,估计大西洋水通过双扩散阶梯向上传输的热通量为0.05~0.6 W/m2,且由下至上呈现逐渐增大的趋势。最后,估算由双扩散造成的垂向涡扩散系数为3×10-6~3.3×10-5 m2/s,且由下至上呈现逐渐减小的趋势。  相似文献   

14.
Various important features could be found on the open ocean deep convection and the subsequent deep water formation from large eddy simulation (LES), and the results were applied to the East Sea (Japan Sea). It was found that under a strong cold wind outburst with the heat flux of 1000 Wm−2 for 5 days generates a deep convection which can penetrate to the depth 1500 m, but under the continuous cooling with the heat flux of 250 Wm−2 the growth of a mixed layer is suppressed at 700 m. The effects of the spatial and temporal variations of the surface forcing were investigated with regard to the penetrative depth of convection, the generation of baroclinic eddies, the volume of the water mass formation, and the intensity of the rim current. The deep water formations in the intermediate and deep layer of the East Sea were explained in terms of the simulation results, and the intensity of the consequent circulation and the volume of water mass formation were compared with the observation data. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

15.
本文使用吕宋海峡以东的潜标观测的长达1年的海流数据,重点对该海域海流的高频波动(潮流)的垂向分布及其时间变化特征进行了分析,结果表明:该海域次表层(100～160 m)的潮动能比中层(1 550 m)和深层(2 560 m)大1～2个数量级,近底层(4 040 m)的潮动能略大于中、深层;次表层为不正规半日潮流,中、深层为不正规全日潮流;各层次潮动能均在夏季(6?9月)和冬季(2?3月)增强,与M2分潮和K1分潮在夏季和冬季的增强相对应;各层次海流的高频波动以顺时针旋转为主,次表层海流近惯性周期接近当地理论惯性周期,中、深层略小于当地理论惯性周期。  相似文献   

16.
The expression for the bottom convection intensity is derived from the equality of the advective vertical flux of H2S within 1000–2000 m to the diffusion turbulent flow close to the H2S zone upper boundary. The upwelling rate, which is expressed via the H2S concentration in deep waters and the gradient of the H2S concentration near the upper boundary, is 10–4 cm/s. It is shown that the H2S diffusion flux in deep waters is an order less than the advective one. The conclusion that below 1000 m the age of H2S does not exceed 30 years and H2S reaches the upper boundary in approximately 150 years is derived.Translated by Mikhail M. Trufanov.  相似文献   

17.
The paper discusses the parameters derived through deep-sea precision CTD-probings, characteristic of the structure of the near-bottom boundaries layer, specifically, the depth of the layer's upper boundary and the mean vertical potential temperature/salinity gradients, as well as the density ratio over the layer of the near-bottom convection. The peculiarities of the parameters' spatial distribution have been identified. The conclusion derived from the analysis of the model implies that the near-bottom boundary layer occurs, aside from the presence of the bottom geothermal heat flux, due to the strong dependence of the Bosphorus salt flux on stratification. The dependence of the Black Sea buoyancy flux and vertical diffusion coefficient on depth has been estimated. Translated by Vladimir A. Puchkin  相似文献   

18.
宋伟  王玉  崔凤娟  谢强 《海洋与湖沼》2019,50(4):752-758
南海上层海洋热力结构年代际变化的研究,是海气相互作用与变化研究的热点之一,对南海区域及更大范围的气候异常的研究和南海海洋环流年际变化的研究都具有重要意义。本文采用多套海温、流场和海气界面通量资料,基于热平衡方程和统计分析方法,分析了南海上层热含量的年代际变化,研究了南海上层热含量影响因子的变化特征,比较了混合层及混合层以下热含量变化的异同,进而探讨了影响因子在混合层及混合层以下的不同作用;利用区域积分海温方程后得到的热量收支方程,诊断南海内区不同海域的热收支方程中的各项,发现了不同海域在影响热收支的物理过程方面存在差异。结果表明:南海混合层的热含量的变化主要受海气界面热通量的影响,夹卷效应在热含量的变化中也有接近1/3的贡献。在整个上层400m的热含量变化中,平流效应占据了主导地位。  相似文献   

19.
In high-latitude oceans with seasonal ice cover, the ice and the low-salinity mixed layer form an interacting barrier for the heat flux from the ocean to the atmosphere. The presence of a less dense surface layer allows ice to form, and the ice cover reduces the heat loss to the atmosphere. The ice formation weakens the stability at the base of the mixed layer, leading to stronger entrainment and larger heat flux from below. This heat transport retards, and perhaps stops, the growth of the ice cover. As much heat is then entrained from below as is lost to the atmosphere. This heat loss further reduces the stability, and unless a net ice melt occurs, the mixed layer convects. Two possibilities exist: (1) A net ice melt, sufficient to retain the stability, will always occur and convection will not take place until all ice is removed. The deep convection will then be thermal, deepening the mixed layer. (2) The ice remains until the stability at the base of the mixed layer disappears. The mixed layer then convects, through haline convection, into the deep ocean. Warm water rises towards the surface and the ice starts to melt, and a new mixed layer is reformed. The present work discusses the interactions between ice cover and entrainment during winter, when heat loss to the atmosphere is present. One crucial hypothesis is introduced: “When ice is present and the ocean loses sensible heat to the atmosphere and to ice melt, the buoyancy input at the sea surface due to ice melt is at a minimum”. Using a one-dimensional energy-balance model, applied to the artificial situation, where ice melts directly on warmer water, it is found that this corresponds to a constant fraction of the heat loss going to ice melt. It is postulated that this partitioning holds for the ice cover and the mixed layer in the high-latitude ocean. When a constant fraction of heat goes to ice melt, at least one deep convection event occurs, before the ice cover can be removed by heat entrained from below. After one or several convection events the ice normally disappears and a deep-reaching thermal convection is established. Conditions appropriate for the Weddell Sea and the Greenland Sea are examined and compared with field observations. With realistic initial conditions no convection occurs in the warm regime of the Weddell Sea. A balance between entrained heat and atmospheric heat loss is established and the ice cover remains throughout the winter. At Maud Rise convection may occur, but late in winter and normally no polynya can form before the summer ice melt. In the central Greenland Sea the mixed layer generally convects early in winter and the ice is removed by melting from below as early as February or March. This is in agreement with existing observations.  相似文献   

20.
The term cabbeling describes the convection that can occur when a mixture of two oceanic water masses is more dense than both of the parent water masses. When the two water masses are situated one above the other, the temperature and salinity distributions are in the correct senses for double-diffusive convection to occur and it is found that the prime effects of the nonlinearity of the equation of state are firstly to drive a greater level of double-diffusive convective activity in the lower layer than in the upper layer, and secondly, to make the lower edge of the interfacial region less gravitationally stable. Both of these effects cause the interface to migrate upwards as the lower layer grows at the expense of the upper layer. We introduce a nondimensional parameter δ (called the cabbeling parameter) which represents the importance of the nonlinearity of the equation of state:—δ is zero when the equation of state is linear and when cabbeling is normally thought to be possible, δ is greater than unity. Experiments set up in both the finger and diffuse sense show how the nondimensional measure of the upward interface migration (called the “entrainment” parameter E) varies with the density anomaly ration R? for various values of δ between zero and 2.0 and that no abrupt change in this behaviour occurs at δ = 1.0. It is impossible to explain these observation by neglecting double-diffusive convection and considering only the convection driven by the conventional cabbeling instability. The successful interpretation of the laboratory results relies on considering the effects of a non-linear equation of state on the double-diffusive convection process.  相似文献   

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