首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 250 毫秒
1.
Possible source of the antarctic bottom water in the Prydz Bay Region   总被引：4，自引：0，他引：4  
It has been inferred that the Prydz Bay region is one of the source regions of Antarctic Bottom Water (AABW) based on rather indirect evidence. In order to examine this inference, we investigate the hydrographic condition of the bay based mainly on XCTD data obtained during the Japanese Whale Research Program in the Antarctic (JARPA). The JARPA hydrographic data reveal Circumpolar Deep Water (CDW), which is a salty, warm water mass approaching the shelf break, and capture Modified CDW (MCDW) intruding into the shelf water. AABW production requires mixing of CDW and cold shelf water saltier than 34.6 psu, which is a saltier type of Low Salinity Shelf Water (LSSW). Saltier LSSW is observed near the bottom over the shelf, being mixed with MCDW. We further identify saltier LSSW near the shelf break. This saltier LSSW appears close enough to unmodified CDW to be mixed with it over the continental slope, indicating a possible source of AABW in Prydz Bay.  相似文献   

2.
Stable oxygen isotopic composition of sea water and stable carbon isotopes of dissolved inorganic carbon (DIC) on the continental shelf in the southern Weddell Sea are presented. Using the stations sampled during the summer 1995 two sections can be constructed, one closely parallel to the ice shelf edge and the other perpendicular to the upper continental slope. Generally, δ18O values clearly separate between different shelf water masses depending on the content of meteoric meltwater added during melting of glacial ice. Extrapolation of the mixing line between the cores of High Salinity Shelf Water (HSSW) and supercooled Ice Shelf Water (ISW) reveals δ18O values of the glacial ice of −27‰, whereas extrapolation of the mixing line between the δ18O values of the most-saline HSSW and lowest temperature ISW results in δ18O values of −34‰ for glacial ice. These values point to an origin of meltwater from below the ice shelf, where ice is less depleted in 18O, since deep beneath the ice shelf close to the grounding line, values may reach −40‰. If values between −34 and −27‰ are used as δ18O end member values for glacial ice, the amount of meltwater from the ice shelf that adds to the formation of ISW off the Filchner–Ronne Ice Shelf ranges from 0.2 to 0.8%, in agreement with previous studies based on δ18O and 4He. Carbon isotopic fractionation due to gas exchange between the atmosphere and the ocean at cold temperatures results in Δδ13CDIC values of 0.20±0.17‰ for Weddell Sea Deep Water, the water mass that ventilates the global abyssal ocean, typically defined as Antarctic Bottom Water (AABW). This confirms the low end of the range estimated previously (0.2–0.4‰), and thus corroborates the dominance of biology in shaping the deep and bottom water δ13C signal. It has been hypothesized that different modes of glacial/interglacial Antarctic bottom water formation may be separated by different stable isotopic compositions of deep-sea foraminiferal calcite. Here I show that differences between Δδ13C and δ18O values of HSSW and ISW, both of which contribute to bottom water formation today, are too small to be resolved in deep and bottom water masses. Therefore, glacial/interglacial changes in relative proportions of these water masses in Antarctic deep and bottom water cannot be separated by stable isotopes of fossil benthic foraminiferal calcite.  相似文献   

3.
Temperature, salinity and chlorofluorocarbons (CFCs) 11, 12 and 113 were measured on a line of stations along the front of the Ross Ice Shelf in the austral summers of 1984, 1994 and 2000. Water mass distributions were similar each year but with high variability in the cross-sectional areas. CFC concentrations increased and salinity decreased with time throughout the water column. CFC saturation levels in the shelf and surface waters also increased with time and ranged from 43% to 90%. The undersaturation was due to inflow of low-CFC modified Circumpolar Deep Water, gas exchange limited by sea ice cover and isolation of water from the atmosphere beneath the ice shelf. The residence time of dense shelf waters resulting from sea ice formation is less well constrained by the chemical data than is the strong flow into the Ross Ice Shelf cavity. Shelf waters are transformed over about 3.5 years, by net basal melting of the ice shelf, into fresher Ice Shelf Water (ISW), which emerges as a large plume near the central ice front at temperatures below the sea surface freezing point. We estimate an average ISW production rate of 0.86 Sv and an average net basal melt rate of 60 km3/year for the Ross Ice Shelf exceeding a 300 m draft (75% of the ice cavity) during recent decades from box and stream tube models fit to all of the CFC and salinity data. Model fits to the individual data sets suggest ISW production and net basal melt rate variability due to interannual changes on a shorter time scale than our observations. ISW production based on the CFC budget is better constrained than net basal melting based on thermohaline data, with a heat budget yielding a rate of only 20 km3/yr. Reconciling differences between apparent freshwater and temperature changes under the ice shelf involves considerations of mixing, freezing and the flow of meltwater across the ice shelf grounding line.  相似文献   

4.
利用中国第九次南大洋考察中南极普里兹湾及其邻近海域的CTD资料,分析研究了调查海域的水文结构特征及其该区南极底层水(AABW)的来源.研究结果表明,在研究海域,深水洋区近表层流由西向东流,而在普里兹湾内存在一个气旋型涡.水文结构中最明显的海洋学特征是:(1)绕极深层水(CDW)的涌升现象明显,涌升最强的位置是麦克罗伯逊地以北海域,最明显的深度是50～200m层,暖水涌升将冬季冷水分隔成南北两部分,并在其中形成孤立的暖水块;(2)陆缘水边界明显,这是绕极深层水与南极冷水之间形成的锋面,一般处在次表层水中,大致位于64°～66°S之间;(3)存在着双跃层结构.观测期间,普里兹湾以北探水海域存在着南极底层水,其来源可能有二:一为当地形成,二为源于威德尔海和罗斯海.  相似文献   

5.
The first vertical profiles of chlorofluoromethanes (Freons F11 and F12) measured during the austral summer 1987 (INDIGO-3 cruise) in the region of Enderby Land (30°E) and the Princess Elizabeth Trough (90°E) arc presented in relation to hydrological and geochemical characteristics. In the open ocean, transient tracer penetration reaches 1000 m. Off the West Ice Shelf and Enderby Land, a significant decrease in Freons is found below the cold Winter Water and just above the deep oxygen minimum and temperature maximum of the upper Circumpolar Deep Water (200–400 m). In the region off MacRobertson Land, where the oxygen minimum is deeper (1000 m), the Freon gradients are less abrupt. In deep open ocean waters, no Freons were detected in the core of the Circumpolar Deep Water. However, near the continental shelf, we have encountered Freon minima associated with salinity maxima, indicating significant mixing between deep and (recent) ventilated waters. Over the whole water column, a strong zonal contrast emerges in tracer distributions between stations situated to the east and to the west of MacRobertson Land (65°E), which may be associated with the Weddell Gyre extension. Freon maxima associated with oxygen maxima and temperature and salinity minima that characterize Antarctic Bottom Water (AABW) have been found over all the region studied; the tracers indicate three main bottom waters that are related to Weddell Sea, Ross Sea and local origins. At two stations located on the edge of the continental shelf, Freon measurements suggest that the AABW formation was recent, and the tracers' continuity reveals a preferential westward flow of bottom waters. Although it is clear that bottom water formation takes place around 60–70°E, the information is too sparse to specify the source regions.  相似文献   

6.
南极普里兹湾及其邻近海域水团研究   总被引：3，自引：3，他引：0  
普里兹湾及其邻近海域是中国南大洋调查研究的传统优势海域与重点区域。围绕夏季表层水、冬季水、陆架水、绕极深层水、南极底层水、普里兹湾底层水、冰架水等研究海区主要水团的特征和分布,总结了前人在南极普里兹湾及其邻近海域基于调查资料开展的水团研究中所取得的成果。研究表明,前人在对陆架水的示性指标界定上,将陆架水是否区分为高盐陆架水和低盐陆架水存在较大争议,在高盐陆架水和普里兹湾底层水的定义上存在重叠;目前尚没有证据表明绕极深层水向南可以伸展到普里兹湾的陆架区域,也没有发现在普里兹湾附近海域生成南极底层水的直接证据。  相似文献   

7.
普里兹湾附近绕极深层水和底层水及其运动特征   总被引：7，自引：5，他引：7  
利用中国第15次南极科学考察科学考察队的CTD全深度观测资料(1998年11月至1999年2月),分析并讨论了普里兹湾以北的南大洋海域内,绕极深层水(CDW)和南极底层水(AABW)的物理特性及其空间分布.同时还与历史上其他学者的发现进行了比较.指出了在研究海域内,CDW在100～2000m之间从北向南扩展,其高温核(t>1.2℃)和高盐核(S>34.7)在75°E断面上最为深厚,向南扩展得最远;而AABW则在2500m以深由陆坡底部向北扩展,σθ>27.875的高密度水体在70°E断面上最为深厚,向北扩展得最远.此外还通过实测的CTD资料证实了CDW和AABW的经向环流特征,以及它们与迪肯流环(Deaconcell)、亚极地流环和深层流环的一致性.  相似文献   

8.
自50年代后期以来国际上对普里兹湾区海洋过程的调査研究不断加强(Zverev,1959,1963; Izvekov,1959),尤其是进入80年代后,由于在现场考察中采用了CTD系统和浮标测流系统,人们对该区海洋过程的认识有了长足的进步。但由于该海区的热盐结构有非常显著的时空变化(Kornilov,1971; Smith et al.,1984; Middleton and Hamphries,1989;乐肯堂等,1996,1997),因而对该海区水团和环流中的若干重要问题,例如环流子午向分布向题,底层水形成问题,热盐结构时空变化间题等,仍缺乏足够的了解。 在乐肯堂等(1996,1997)的文章中,我们主要根据中国第六次(CNARE-Ⅵ,1989-1990)和第七次(CNARE-Ⅶ,1990-1991)南极考察中的海洋调查资料,分析了普里兹湾区的热盐结构、环流性质和混合过程。在本文中,我们将着重分析中国第八次(CNARE-Ⅷ,1991-1992)和第九次(CNARE-Ⅸ,1992-1993)南极考察中的CTD资料,并结合CNARE-Ⅵ,Ⅶ的资料,对该区的水团和环流的时空变化问题进行初步探讨。 关于CNARE-Ⅵ和 CNARE-Ⅶ的资料概况可见乐肯堂等(1996),不再重述。CNARE-Ⅷ的CTD断面设置与 CNARE-Ⅶ相同[参见乐肯堂等(1996)];但观测工作分为两个阶段:第一阶段从1991年12月31日至1992年1月5日,完成了从78°E至108°E共6个断面的测站;第二阶段,从1992年1月23日至25日,完成了68°E和73°E两个断面的测站。CNARE-Ⅸ的CTD断面如图1所示;观测工作也分两个阶段:第一阶段从1993年1月11日至1月15日,完成了I、Ⅱ、Ⅲ3个断面的测站;第二阶段从1993年1月29日至2月5日,进行了IV、V、Ⅵ3个断面的观测。这两次考察的CTD观测,每次均分为两个航次,而两个航次之间又都相隔二十余天,因而资料的同步性受到一定的影响。  相似文献   

9.
Transport of warm, nutrient-rich Circumpolar Deep Water (CDW) onto Antarctic continental shelves and coastal seas has important effects on physical and biological processes. The present study investigates the locations of this transport and its dynamics in the Ross Sea with a high-resolution three-dimensional numerical model. The model circulation is forced by daily wind stress along with heat and salt fluxes calculated from atmospheric climatologies by bulk formulae. All surface fluxes are modified by an imposed climatological ice cover. Waters under the Ross Ice Shelf are not included explicitly, but their effect on temperature and salinity is imposed in a buffer zone at the southern end of the model domain. A simple nutrient uptake is calculated based on the climatological chlorophyll distribution and Monod uptake kinetics.Model circulation is strongly affected by bottom topography, due to weak stratification, and agrees with schematics of the general flow and long-term current measurements except near the southern boundary. The sea-surface temperature is similar to satellite estimates except that the warmest simulated temperatures are slightly higher than observations. There is a significant correlation between the curvature of the shelf break and the transport across the shelf break. A momentum term balance shows that momentum advection helps to force flow across the shelf break in specific locations due to the curvature of the bathymetry (that is, the isobaths curve in front of the flow). For the model to create a strong intrusion of CDW onto the shelf, it appears two mechanisms are necessary. First, CDW is driven onto the shelf at least partially due to momentum advection and the curvature of the shelf break; then, the general circulation on the shelf takes the CDW into the interior.  相似文献   

10.
P. T. Harris 《Marine Geology》2000,170(3-4):317-330
Biosiliceous sediments sampled from a submarine valley system on the continental shelf of East Antarctica contain intervals of ripple cross-lamination interspersed with massively bedded units. Based on radiocarbon dates from one core collected on the Mac.Robertson Shelf, the most intensely cross-laminated sediments were deposited between 6 and 3.5 kyr BP, with isolated cross-laminae deposited at other times in the Holocene. The cross-laminated sediments are interpreted here as a signal of episodic density currents flowing across the outer shelf, which result from the formation of high salinity shelf water (HSSW). This HSSW is formed in winter by brine rejection during sea ice formation and by the exchange and cooling of upwelled saline slope water, and it contributes to the bottom water produced along the continental margin of Antarctica. If this interpretation of the cross-laminae is correct, then bottom water formation and export from the East Antarctic shelf has exhibited temporal, and probably also spatial, variability throughout the Holocene. Such variability would have implications for oceanographers attempting to quantify Antarctic bottom water production rates based only on present day observations.  相似文献   

11.
Hydrographic, current meter and ADCP data collected during two recent cruises in the South Indian Ocean (RRS Discovery cruise 200 in February 1993 and RRS Discovery cruise 207 in February 1994) are used to investigate the current structure within the Princess Elizabeth Trough (PET), near the Antarctic continent at 85°E, 63–66°S. This gap in topography between the Kerguelen Plateau and the Antarctic continent, with sill depth 3750 m, provides a route for the exchange of Antarctic Bottom Water between the Australian–Antarctic Basin and the Weddell–Enderby Basin. Shears derived from ADCP and hydrographic data are used to deduce the barotropic component of the velocity field, and thus the volume transports of the water masses. Both the Southern Antarctic Circumpolar Current Front (SACCF) and the Southern Boundary of the Antarctic Circumpolar Current (SB) pass through the northern PET (latitudes 63 to 64.5°S) associated with eastward transports. These are deep-reaching fronts with associated bottom velocities of several cm s-1. Antarctic Bottom water (AABW) from the Weddell–Enderby Basin is transported eastwards in the jets associated with these fronts. The transport of water with potential temperatures less than 0°C is 3 (±1) Sv. The SB is shown to meander in the PET, caused by the cyclonic gyre immediately west of the PET in Prydz Bay. The AABW therefore also meanders before continuing eastwards. In the southern PET (latitudes 64.5 to 66°S) a bottom intensified flow of AABW is observed flowing west. This AABW has most likely formed not far from the PET, along the Antarctic continental shelf and slope to the east. Current meters show that speeds in this flow have an annual scalar mean of 10 cm s-1. The transport of water with potential temperatures less than 0°C is 20 (±3) Sv. The southern PET features westward flow throughout the water column, since the shallower depths are dominated by the flow associated with the Antarctic Slope Front. Including the westward flow of bottom water, the total westward transport of the whole water column in the southern PET is 45 (±6) Sv.  相似文献   

12.
《Ocean Modelling》2001,3(1-2):51-65
Two mechanisms contribute to the formation of Antarctic bottom water (AABW). The first, and probably the most important, is initiated by the brine released on the Antarctic continental shelf during ice formation which is responsible for an increase in salinity. After mixing with ambient water at the shelf break, this salty and dense water sinks along the shelf slope and invades the deepest part of the global ocean. For the second one, the increase of surface water density is due to strong cooling at the ocean–atmosphere interface, together with a contribution from brine release. This induces deep convection and the renewal of deep waters. The relative importance of these two mechanisms is investigated in a global coupled ice–ocean model. Chlorofluorocarbon (CFC) concentrations simulated by the model compare favourably with observations, suggesting a reasonable deep water ventilation in the Southern Ocean, except close to Antarctica where concentrations are too high. Two artificial passive tracers released at surface on the Antarctic continental shelf and in the open-ocean allow to show clearly that the two mechanisms contribute significantly to the renewal of AABW in the model. This indicates that open-ocean convection is overestimated in our simulation. Additional experiments show that the amount of AABW production due to the export of dense shelf waters is quite sensitive to the parameterisation of the effect of downsloping and meso-scale eddies. Nevertheless, shelf waters always contribute significantly to deep water renewal. Besides, increasing the P.R. Gent, J.C. McWilliams [Journal of Physical Oceanography 20 (1990) 150–155] thickness diffusion can nearly suppress the AABW formation by open-ocean convection.  相似文献   

13.
Transient tracer data (tritium, CFC11 and CFC12) from the southern, central and northwestern Weddell Sea collected during Polarstern cruises ANT III-3, ANT V-2/3/4 and during Andenes cruise NARE 85 are presented and discussed in the context of hydrographic observations. A kinematic, time-dependent, multi-box model is used to estimate mean residence times and formation rates of several water masses observed in the Weddell Sea.Ice Shelf Water is marked by higher tritium and lower CFC concentrations compared to surface waters. The tracer signature of Ice Shelf Water can only be explained by assuming that its source water mass, Western Shelf Water, has characteristics different from those of surface waters. Using the transient nature of tritium and the CFCs, the mean residence time of Western Shelf Water on the shelf is estimated to be approximately 5 years. Ice Shelf Water is renewed on a time scale of about 14 years from Western Shelf Water by interaction of this water mass with glacial ice underneath the Filchner-Ronne Ice shelf. The Ice Shelf Water signature can be traced across the sill of the Filchner Depression and down the continental slope of the southern Weddell Sea. On the continental slope, new Weddell Sea Bottom Water is formed by entrainment of Weddell Deep Water and Weddell Sea Deep Water into the Ice Shelf Water plume. In the northwestern Weddell Sea, new Weddell Sea Bottom Water is observed in two narrow, deep boundary currents flowing along the base of the continental slope. Classically defined Weddell Sea Bottom Water (θ ≤ −0.7°C) and Weddell Sea Deep Water (−0.7°C ≤ θ ≤ 0°C) are ventilated from the deeper of these boundary currents by lateral spreading and mixing. Model-based estimates yield a total formation rate of 3.5Sv for new Weddell Sea Bottom Water (θ = −1.0°C) and a formation rate of at least 11Sv for Antarctic Bottom Water (θ = −0.5°C).  相似文献   

14.
We analyze absolute velocities on the continental shelf off Cape Adare, in the western sector of the Ross Sea (Antarctica). Such a velocity field is here inferred by using a novel inverse method of absolute velocity determination, namely the tracer PV method, related to potential vorticities of temperature and salinity. This theoretical choice allows us to directly use in situ temperature and salinity data. Moreover, it avoids high-order derivatives, which can give large uncertainties that affect estimates made using previous approaches. The tracer PV method also allows us to separately estimate the steady and non-diffusive component and the unsteady and diffusive components of the flow. The western sector of the Ross Sea is characterized by a surface layer of Antarctic Surface Water over layers of Low Salinity Shelf Water and High Salinity Shelf Water, flowing northward with average velocities ～6–7 cm/s. At ～200 m depth an intrusion of warmer and saltier Circumpolar Deep Water is also evident in our data. The steady absolute velocities are in good agreement with those obtained from the classical Margules equation, in particular regarding the northward flux of the High Salinity Shelf Water. Furthermore, velocities due to diffusive processes and mesoscale activity are discussed. Finally, a steady “thermal” approximation is discussed; it allows for a qualitative check of the results by means of temperature horizontal sections only.  相似文献   

15.
The Adare Trough, located 100 km NE of Cape Adare, Antarctica, is the extinct third arm of a Tertiary spreading ridge that separated East from West Antarctica. We use seismic reflection data, tied to DSDP Site 274, to link our seismic stratigraphic interpretation to changes in ocean-bottom currents, Ross Sea ice cover, and regional tectonics through time. Two extended unconformities are observed in the seismic profiles. We suggest that the earliest hiatus (early Oligocene to Mid-Miocene) is related to low sediment supply from the adjacent Ross Shelf, comprised of small, isolated basins. The later hiatus (mid-Miocene to late Miocene) is likely caused by strong bottom currents sourced from the open-marine Ross Sea due to increased Antarctic glaciation induced by mid-Miocene cooling (from Mi-3). Further global cooling during the Pliocene, causing changes in global ocean circulation patterns, correlates with Adare Basin sediments and indicate the continuing but weakened influence of bottom currents. The contourite/turbidite pattern present in the Adare Trough seismic data is consistent with the 3-phase contourite growth system proposed for the Weddell Sea and Antarctic Peninsula. Multibeam bathymetry and seismic reflection profiles show ubiquitous volcanic cones and intrusions throughout the Adare Basin that we interpret to have formed from the Oligocene to the present. Seismic reflection profiles reveal trans-tensional/strike-slip faults that indicate oblique extension dominated Adare Trough tectonics at 32–15 Ma. Observed volcanism patterns and anomalously shallow basement depth in the Adare Trough area are most likely caused by mantle upwelling, an explanation supported by mantle density reconstructions, which show anomalously hot mantle beneath the Adare Trough area forming in the Late Tertiary.  相似文献   

16.
The distribution and circulation of water masses in the region between 6°W and 3°E and between the Antarctic continental shelf and 60°S are analyzed using hydrographic and shipboard acoustic Doppler current profiler (ADCP) data taken during austral summer 2005/2006 and austral winter 2006. In both seasons two gateways are apparent where Warm Deep Water (WDW) and other water masses enter the Weddell Gyre through the Lazarev Sea: (a) a probably topographically trapped westward, then southwestward circulation around the northwestern edge of Maud Rise with maximum velocities of about 20 cm s−1 and (b) the Antarctic Coastal Current (AntCC), which is confined to the Antarctic continental shelf slope and is associated with maximum velocities of about 25 cm s−1.Along two meridional sections that run close to the top of Maud Rise along 3°E, geostrophic velocity shears were calculated from CTD measurements and referenced to velocity profiles recorded by an ADCP in the upper 300 m. The mean accuracy of the absolute geostrophic velocity is estimated at ±2 cm s−1. The net baroclinic transport across the 3°E section amounts to 20 and 17 Sv westward for the summer and winter season, respectively. The majority of the baroclinic transport, which accounts for ∼60% of the total baroclinic transport during both surveys, occurs north of Maud Rise between 65° and 60°S.However, the comparison between geostrophic estimates and direct velocity measurements shows that the circulation within the study area has a strong barotropic component, so that calculations based on the dynamic method underestimate the transport considerably. Estimation of the net absolute volume transports across 3°E suggests a westward flow of 23.9±19.9 Sv in austral summer and 93.6±20.1 Sv in austral winter. Part of this large seasonal transport variation can be explained by differences in the gyre-scale forcing through wind stress curl.  相似文献   

17.
The identification of bacterial community structure has led, since the beginning of the 1990s, to the idea that bacterioplankton populations are stratified in the water column and that diverse lineages with mostly unknown phenotypes dominate marine microbial communities. The diversity of depth-related assemblages is also reflected in their patterns of activities, as bacteria affiliated to different groups can express different activities in a given ecosystem. We analysed bacterial assemblages (DGGE fingerprinting) and their activities (prokaryotic carbon production, protease, phosphatase, chitinase, beta-glucosidase and lipase activities) in two areas in the Ross Sea, differing mainly in their productivity regime: two stations are located in the Terra Nova Bay polynya area (highly productive during summer) and two close to Cape Adare (low phytoplankton biomass and activity). At every station a pronounced stratification of bacterial assemblages was identified, highlighting epipelagic communities differing substantially from the mesopelagic and the bathypelagic communities. Multivariate analysis suggested that pressure and indirectly light-affected variables (i.e. oxygen and fluorescence) had a great effect on the bacterial communities outcompeting the possible influences of temperature and dissolved organic carbon concentration. Generally activities decreased with depth even though a signal of the Circumpolar Deep Water (CDW) at one of the northern stations corresponded to an increase in some of the degradative activities, generating some ‘hot spots’ in the profile. We also found that similar assemblages express similar metabolic requirements reflected in analogous patterns of activity (similar degradative potential and leucine uptake rate). Furthermore, the presence of eukaryotic chloroplasts’ 16S rDNA in deep samples highlighted how in some cases the dense surface-water formation (in this case High Salinity Shelf Water—HSSW) and downwelling can affect, at least for some phylotypes, the bacterial (16S rDNA based) community structure of the dark ocean.  相似文献   

18.
南大洋海洋环流系统由南极底层水AABW、南极绕极流ACC、南极表层水AASW、绕极深层水CDW组成,它们在全球气候调节中扮演重要角色。随着科考技术的进步,有关南大洋古环流研究越来越多,研究主要集中在温度、盐度、流向和影响作用等方面。研究侧重内容不同所采取的手段和方法也有差别,南大洋古环流研究方法包括古生物法、地球化学法、数值模拟、沉积法、实测资料等。本文就这些研究方法做一简单综述,以期强调南大洋在全球大洋历史中的作用。  相似文献   

19.
Dense water formation and circulation in the Barents Sea   总被引：1，自引：0，他引：1  
Dense water masses from Arctic shelf seas are an important part of the Arctic thermohaline system. We present previously unpublished observations from shallow banks in the Barents Sea, which reveal large interannual variability in dense water temperature and salinity. To examine the formation and circulation of dense water, and the processes governing interannual variability, a regional coupled ice-ocean model is applied to the Barents Sea for the period 1948-2007. Volume and characteristics of dense water are investigated with respect to the initial autumn surface salinity, atmospheric cooling, and sea-ice growth (salt flux). In the southern Barents Sea (Spitsbergen Bank and Central Bank) dense water formation is associated with advection of Atlantic Water into the Barents Sea and corresponding variations in initial salinities and heat loss at the air-sea interface. The characteristics of the dense water on the Spitsbergen Bank and Central Bank are thus determined by the regional climate of the Barents Sea. Preconditioning is also important to dense water variability on the northern banks, and can be related to local ice melt (Great Bank) and properties of the Novaya Zemlya Coastal Current (Novaya Zemlya Bank). The dense water mainly exits the Barents Sea between Frans Josef Land and Novaya Zemlya, where it constitutes 63% (1.2 Sv) of the net outflow and has an average density of 1028.07 kg m−3. An amount of 0.4 Sv enters the Arctic Ocean between Svalbard and Frans Josef Land. Covering 9% of the ocean area, the banks contribute with approximately 1/3 of the exported dense water. Formation on the banks is more important when the Barents Sea is in a cold state (less Atlantic Water inflow, more sea-ice). During warm periods with high throughflow more dense water is produced broadly over the shelf by general cooling of the northward flowing Atlantic Water. However, our results indicate that during extremely warm periods (1950s and late 2000s) the total export of dense water to the Arctic Ocean becomes strongly reduced.  相似文献   

20.
中国南大洋水团、环流和海冰研究进展(1995-2002)   总被引：2，自引：0，他引：2  
总结了1995年以来中国在南大洋物理海洋学研究和南极海冰研究中所取得的成果。普里兹湾海区是中国南大洋研究的重点区域，研究表明，在该海区存在显著的深层水涌升和陆架水北扩现象，某些年份深层水与陆架水混合后产生了较重的水体，但是尚未发现生成南极底层水的直接证据。在普里兹湾所处的印度洋区段，亚热带锋、亚南极锋和极锋表现出显著的时空变化，特别是不同年份的锋面位置存在较大的摆动。该海区的南极绕极流既是风生的，也受到密度场的影响。在凯尔盖朗海台的地形引导作用下，南极绕极流表现出显著的非纬向性特征。南极海冰除了显著的季节变化以外，也表现出长期变化的趋势。此变化与海洋、大气中的其它变化有一定的相关性，表现为两极海冰涛动、南方海洋涛动等多种变化模态，对我国气候也有一定的影响。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号