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 15 毫秒
1.
The circulation pattern and volume transports in the eastern Weddell Gyre are estimated on the basis of hydrographic data collected by R.V. Polarstern between 1989 and 1996. In the northeastern edge of the Weddell Gyre, eastward-flowing water masses from the Antarctic Circumpolar Current and the Weddell Sea converge. Due to the strong effect of topographic constraints on ocean currents in the weakly stratified waters of high latitudes, the wedge-like structure of the Southwest Indian Ridge can cause the convergence. The increased shear leads to instabilities of the current at the eastern end of the ridge, which produce an intense mesoscale eddy field between 15° and 30°E. In the eddies, water from the Weddell cold regime and the Antarctic Circumpolar Current waters mix and form the water masses of the Weddell warm regime. These waters are advected southward and flow towards the westward southern rim current, which is driven by the Antarctic eastwind band. Hence, there is not a continous flow from the northern to the southern rim, but a decay of the mean flow in the northeast and a reformation in the south. Volume transports across the Greenwich Meridian, estimated on the basis of a combined CTD/ADCP data set, result in an eastward flow of 61 Sv in the northern rim current and a westward return flow of 66 Sv in the southern part of the gyre. The transport is about twice as high as previous estimates between Kapp Norvegia and the northern tip of the Antarctic Pensinsula, indicating a significant gyre circulation north of 70°S.  相似文献   

2.
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   

3.
The salinity maximum of the Warm Deep Water advecting into the Weddell Sea lies about 200 m below the temperature maximum and an NO minimum. The NO minimum is horizontally as well as vertically resolved on two sections towards the eastern and southern coast of the Weddell Sea, one towards Cap Norvegia, the other towards the Filchner Ice Shelf, whereas the temperature and salinity maxima are horizontally resolved on the former section only. Thus NO is a valuable complementary tool in studying the boundary current along the coast of the Weddell Sea. The NO signal indicates a non-continuity within the boundary current, as the minimum in the downstream section (less than 480 μmol kg−1 ) is deeper than the upstream one ( more than 490 μmol kg−1). The temperature maximum as well as the NO minimum descend from a depth of about 400 m in the Cap Norvegia section to about 600 m in the Filchner Ice Shelf section, the salinity maximum being correspondingly lowered. A plot of NO vs. salinity shows a continuous mixing line between Warm Deep Water and the freshest part of the Winter Water interval, thus essentially displaying Winter Water as itself lying on a mixing line. This indicates that Warm Deep Water is being advected well into the winter surface layer.  相似文献   

4.
The circulation and hydrography of the north-eastern North Atlantic has been studied with an emphasis on the upper layers and the deep water types which take part in the thermohaline overturning of the Oceanic Conveyor Belt. Over 900 hydrographic stations were used for this study, mainly from the 1987–1991 period. The hydrographic properties of Subpolar Mode Water in the upper layer, which is transported towards the Norwegian Sea, showed large regional variation. The deep water mass was dominated by the cold inflow of deep water from the Norwegian Sea and by a cyclonic recirculation of Lower Deep Water with a high Antarctic Bottom Water content. At intermediate levels the dominating water type was Labrador Sea Water with only minor influence of Mediterranean Sea Water. In the permanent pycnocline traces of Antarctic Intermediate Water were found.Geostrophic transports have been estimated, and these agreed in order of magnitude with the local heat budget, with current measurements, with data from surface drifters, and with the observed water mass modification. A total of 23 Sv of surface water entered the region, of which 20 Sv originated from the North Atlantic Current, while 3 Sv entered via an eastern boundary current. Of this total, 13 Sv of surface water left the area across the Reykjanes Ridge, and 7 Sv entered the Norwegian Sea, while 3 Sv was entrained by the cold overflow across the Iceland-Scotland Ridge. Approximately 1.4 Sv of Norwegian Sea Deep Water was involved in the overflow into the Iceland Basin, which, with about 1.1 Sv of entrained water and 1.1 Sv recirculating Lower Deep Water, formed a deep northern boundary current in the Iceland Basin. At intermediate depths, where Labrador Sea Water formed the dominant water type, about 2 Sv of entrained surface water contributed to a saline water mass which was transported westwards along the south Icelandic slope.  相似文献   

5.
南极半岛周边海域水团及水交换的研究   总被引：1，自引：1，他引：0  
利用中国第34次南极考察于2018年1–2月在南极半岛周边海域获得的温盐、海流现场观测数据，分析了调查区域主要水团及水交换特征。结果表明，观测区域内主要存在南极表层水、绕极深层水、暖深层水、南极底层水、布兰斯菲尔德海峡底层水。威德尔海的暖深层水、威德尔海深层水通过南奥克尼海台东侧的奥克尼通道、布鲁斯通道和南奥克尼海台西侧的埃斯佩里兹通道进入斯科舍海，其中奥克尼通道的深层海流最强，流速最大可达0.25 m/s，密度较大的威德尔海深层水可以通过此通道进入斯科舍海；布鲁斯通道海流流速约为0.13 m/s，通过此通道的暖深层水位势温度较高；埃斯佩里兹通道海流流速约为0.10 m/s，通过此通道的暖深层水位势温度最低，威德尔海深层水密度最小。在南奥克尼海台东西两侧均观测到南向和北向的海流，但整体上来看，向北的海流和水交换更强。水体进入斯科舍海后，沿着南斯科舍海岭的北侧向西北方向流动，流速约为0.21 m/s。德雷克海峡中的南极绕极流仅有一部分向东进入斯科舍海南部海域，且受到向西流动的暖深层水、威德尔海深层水的影响，斯科舍海南部海域的绕极深层水明显比德雷克海峡中绕极深层水的高温高盐性质弱；受到南极绕极流的影响，南斯科舍海岭北侧的威德尔海深层水比南侧暖。南斯科舍海岭上的水体可能受到北侧绕极深层水、暖深层水，西侧陆架水，东侧冬季水的影响，因此海岭上水体结构较为复杂。  相似文献   

6.
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   

7.
Tritium data were collected between 1985 and 1987 on several cruises of the German research icebreaker “Polarstern” to the Weddell Sea. Maximum tritium concentrations in the surface waters are of the order of 200 mTU. The minimum values observed in the Weddell Sea Deep Water at about 1000 m depth are about 15–40 mTU. The bottom waters show tritium concentrations of about 70–100 mTU in the central gyre, increasing to about 120 mTU in the northwestern corner of the Weddell Sea. The overflowing Ice Shelf Water observed on the continental slope west of the Filchner Depression has tritium concentrations close to those of the surface waters, indicating rapid renewal of this water mass. The data reflect the rapid renewal of the bottom waters in the northwestern corner of the Weddell Sea and the mixing of bottom water from this boundary current into the bottom waters of the central Weddell Gyre.  相似文献   

8.
The traditional image of ocean circulation between Australia and Antarctica is of a dominant belt of eastward flow, the Antarctic Circumpolar Current, with comparatively weak adjacent westward flows that provide anticyclonic circulation north and cyclonic circulation south of the Antarctic Circumpolar Current. This image mostly follows from geostrophic estimates from hydrography using a bottom level of no motion for the eastward flow regime which typically yield transports near 170 Sv. Net eastward transport of about 145 Sv for this region results from subtracting those westward flows. This estimate is compatible with the canonical 134 Sv through Drake Passage with augmentation from Indonesian Throughflow (around 10 Sv).A new image is developed from World Ocean Circulation Hydrographic Program sections I8S and I9S. These provide two quasi-meridional crossings of the South Australian Basin and the Australian–Antarctic Basin, with full hydrography and two independent direct-velocity measurements (shipboard and lowered acoustic Doppler current profilers). These velocity measurements indicate that the belt of eastward flow is much stronger, 271 ± 49 Sv, than previously estimated because of the presence of eastward barotropic flow. Substantial recirculations exist adjacent to the Antarctic Circumpolar Current: to the north a 38 ± 30 Sv anticyclonic gyre and to the south a 76 ± 26 Sv cyclonic gyre. The net flow between Australia and Antarctica is estimated as 157 ± 58 Sv, which falls within the expected net transport of 145 Sv.The 38 Sv anticyclonic gyre in the South Australian Basin involves the westward Flinders Current along southern Australia and a substantial 33 Sv Subantarctic Zone recirculation to its south. The cyclonic gyre in the Australian–Antarctic Basin has a substantial 76 Sv westward flow over the continental slope of Antarctica, and 48 ± 6 Sv northward-flowing western boundary current along the Kerguelen Plateau near 57°S. The cyclonic gyre only partially closes within the Australian–Antarctic Basin. It is estimated that 45 Sv bridges westward to the Weddell Gyre through the southern Princess Elizabeth Trough and returns through the northern Princess Elizabeth Trough and the Fawn Trough – where a substantial eastward 38 Sv current is hypothesized. There is evidence that the cyclonic gyre also projects eastward past the Balleny Islands to the Ross Gyre in the South Pacific.The western boundary current along Kerguelen Plateau collides with the Antarctic Circumpolar Current that enters the Australian–Antarctic Basin through the Kerguelen–St. Paul Island Passage, forming an energetic Crozet–Kerguelen Confluence. Strongest filaments in the meandering Crozet-Kerguelen Confluence reach 100 Sv. Dense water in the western boundary current intrudes beneath the densest water of the Antarctic Circumpolar Current; they intensely mix diapycnally to produce a high potential vorticity signal that extends eastward along the southern flank of the Southeast Indian Ridge. Dense water penetrates through the Ridge into the South Australian Basin. Two escape pathways are indicated, the Australian–Antarctic Discordance Zone near 125°E and the Geelvinck Fracture Zone near 85°E. Ultimately, the bottom water delivered to the South Australian Basin passes north to the Perth Basin west of Australia and east to the Tasman Basin.  相似文献   

9.
The Ulleung Basin is one of three deep basins that are contained within the East/Japan Sea. Current meter moorings have been maintained in this basin beginning in 1996. The data from these moorings are used to investigate the mean circulation pattern, variability of deep flows, and volume transports of major water masses in the Ulleung Basin with supporting hydrographic data and help from a high-resolution numerical model. The bottom water within the Ulleung Basin, which must enter through a constricted passage from the north, is found to circulate cyclonically—a pattern that seems prevalent throughout the East Sea. A strong current of about 6 cms−1 on average flows southward over the continental slope off the Korean coast underlying the northward East Korean Warm Current as part of the mean abyssal cyclonic circulation. Volume transports of the northward East Korean Warm Current, and southward flowing East Sea Intermediate Water and East Sea Proper Water are estimated to be 1.4 Sv (1 Sv=10−6 m3 s−1), 0.8 Sv, and 3.0–4.0 Sv, respectively. Deep flow variability involves a wide range of time scales with no apparent seasonal variations, whereas the deep currents in the northern East Sea are known to be strongly seasonal.  相似文献   

10.
The northward outflow of cold, dense water from the Weddell Sea into the world ocean basins plays a key role in balancing the global heat budget. We estimate the geostrophic flow patterns in the northwestern Weddell Sea using box inverse methods applied to quasi-synoptic hydrographic data collected during the Brazilian DOVETAIL 2000 and 2001 austral summer cruises. The analysis is focused on the variations of the deep Weddell Sea outflow into the Scotia Sea within boxes that bound the main deep gaps over the South Scotia Ridge. To determine the geostrophic volume transports in each box, mass, salt, and heat are conserved within neutral density layers that are not in contact with the atmosphere. Implementing the inverse model and using property anomaly equations weighted by the flow estimate uncertainty our results are consistent with those reported in the literature. A bottom triangle extrapolation method is introduced, which improves the estimated property fluxes through hydrographic sections. In the austral summer of 2000 the transports of Weddell Sea Deep Water (WSDW) through the Philip Passage, Orkney Passage, and southwestern Bruce Passage are 0.01±0.01, 1.15±0.33, and 1.03±0.23 Sv (1 Sv=106 m3 s−1, >0 is northward), respectively. After extrapolation within bottom triangles these transports increase to 0.12±0.03, 3.48±1.81, and 1.20±2.16 Sv. Analysis of the hydrographic data reveal distinct oceanographic conditions over the Philip Passage region, with evidence of mesoscale meanders, warmer and saltier Warm Deep Water (WDW) and colder WSDW observed in 2001 than in 2000. Despite these differences the WSDW transport does not present a significant variation between 2000 and 2001. The WSDW transports through the Philip Passage in 2001 are 0.012±0.001 and 0.113±0.001 Sv after extrapolation within bottom triangles. The circulation derived from the inversion in the austral summer of 2001 suggests a sharp weakening of the barotropic cyclonic flow in the Powell Basin, which may be due to northerly and northeasterly winds associated with an atmospheric low-pressure center located west of the Antarctic Peninsula. We suggest that similar variations in atmospheric forcing may explain changes in the intensity of the cyclonic flow observed in the northwestern Weddell Sea and Powell Basin.  相似文献   

11.
The Vema Channel acts as a major conduit for the equatorward spreading of Antarctic Bottom Water between the Argentine and Brazil Basins. For almost two years the thermal stratification above its saddle depth (4660 m) – called Vema Sill – was recorded by moored thermistors and current meters. The lowest 490 m of the water column was instrumented to monitor the well-developed benthic boundary layer of Antarctic Bottom Water. The latter can be subdivided into Weddell Sea Deep Water on the sea bed and lower Circumpolar Deep Water above it. The data show fluctuations on various scales including periods, each about 1–2 weeks long, when the abyssal stratification virtually disappeared. Assuming a stable ratio between density and temperature, time series of bulk Richardson numbers are estimated from temperature and current shear data. The results suggest a potential for intermittent episodes of locally generated vertical mixing.  相似文献   

12.
Interannual variations of sea level at the Nansei Islands and volume transport of the Kuroshio during 1967–95 are calculated by integrating variations carried by windforced Rossby waves. Effects of eddy dissipation and ocean ridges are considered. Ridge effect is inferred by comparing between the calculated and observed sea levels. The calculation is satisfactory to sea levels and Kuroshio transport for the whole period. They are mostly caused by Rossby waves forced by wind and modified by the ridges, and are due to barotropic wave primarily and the first baroclinic wave secondly. The calculated Kuroshio transport well represents variations of several-year scales with maximums in respective duration of the large meander (LM) of the Kuroshio, as well as bi-decadal variation that transport was small during the non-LM period of 1967–75 and large during the LM-dominant period of 1975–91. Mean volume transport of the subtropical gyre is estimated at 57 Sv (1 Sv = 106 m3s–1) and divided by the Nansei Shoto Ridge into those of the Kuroshio in the East China Sea (25.5 Sv) and a subsurface current east of this ridge (31.5 Sv). The Subtropical Countercurrent and a southward deep current east of the Izu-Ogasawara Ridge are estimated at 16 Sv and 7 Sv, respectively. The calculated transports of the Kuroshio and other subtropical currents reach maximums at every El Niño event due to strong excitement of upwelling barotropic Rossby wave.  相似文献   

13.
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   

14.
A simplified physical model is proposed in this article to describe differences among basins in substance distributions which were not well described by previous simplified models. In the proposed model, the global ocean is divided into the Pacific/Indian Ocean (PI), the Atlantic Ocean (AT), the Southern Ocean and the Greenland/Iceland/Norwegian Sea. The model is consisted of five physical parameters, namely the air-sea gas exchange, the thermohaline circulation, the horizontal and vertical diffusions, and the deep convection in the high-latitude regions. Individual values of these parameters are chosen by optimizing model distribution of natural 14C as a physical tracer. The optimal value for a coefficient of vertical diffusion in the low-latitude region is 7.5 × 10–5 [m2s–1]. Vertical transports by the Antarctic Bottom Water and the North Atlantic Deep Water are estimated at 1.0 Sv and 9.0 Sv. Global-mean air-sea gas exchange time is calculated at 9.0 years. Using these optimal values, vertical profiles of dissolved inorganic carbon without biological production in PI and AT are estimated. Oceanic responses to anthropogenic fluctuations in substance concentrations in the atmosphere induced by the industrialization and nuclear bomb are also discribed, i.e., the effects appear significantly in AT while a signal is extremely weak in PI. A time-delay term is effective to make the PI water older near the bottom boundary.  相似文献   

15.
Several large deployments of neutrally buoyant floats took place within the Antarctic Intermediate (AAIW), North Atlantic Deep Water (NADW), and the Antarctic Bottom Water (AABW) of the South Atlantic in the 1990s and a number of hydrographic sections were occupied as well. Here we use the spatially and temporally averaged velocities measured by these floats, combined with the hydrographic section data and various estimates of regional current transports from moored current meter arrays, to determine the circulation of the three major subthermocline water masses in a zonal strip across the South Atlantic between the latitudes of 19°S and 30°S. We concentrate on this region because the historical literature suggests that it is where the Deep Western Boundary Current containing NADW bifurcates. In support of this notion, we find that a net of about 5 Sv. of the 15–20 Sv that crosses 19°S does continue zonally eastward at least as far as the Mid-Atlantic Ridge. Once across the ridge it takes a circuit to the north along the ridge flanks before returning to the south in the eastern half of the Angola Basin. The data suggest that the NADW then continues on into the Indian Ocean. This scheme is discussed in the context of distributions of dissolved oxygen, silicate and salinity. In spite of the many float-years of data that were collected in the region a surprising result is that their impact on the computed solutions is quite modest. Although the focus is on the NADW we also discuss the circulation for the AAIW and AABW layers.  相似文献   

16.
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   

17.
Morozov  E. G.  Frey  D. I.  Tarakanov  R. Yu. 《Oceanology》2020,60(5):589-592
Oceanology - Measurements of currents and Antarctic Bottom Water properties overflowing the sill from the Weddell to the Scotia Sea are described. The bottom water overflows the sill of one of the...  相似文献   

18.
The Irminger Gyre: Circulation, convection, and interannual variability   总被引：2，自引：0，他引：2  
  相似文献   

19.
The Mascarene Plateau lies in the south-west Indian Ocean between the islands of Mauritius and the Seychelles Bank, and is characterised by a series of shallow banks separated by deep (>1 000 m), narrow channels. The plateau acts as an obstruction to the general ocean circulation in this region, separating the westward-flowing South Equatorial Current (SEC) into two branches downstream of the plateau. In this article, we present the results of a survey conducted along the entire Mascarene Plateau during the Northeast Monsoon, in October–November 2008. In addition, data from Argo floats were used to determine the origin of water masses entering this region. The plateau contains three gaps through which branches of the SEC are channelled. The northern, central and southern gaps receive 14.93 Sv, 14.41 Sv and 6.19 Sv, respectively. Although there are differences in water-mass properties to the west and east of the Mascarene Plateau due to mixing, the SEC acts as a sharp boundary between water masses of southern and northern Indian Ocean origin. Mixing occurs in the central gap between intermediate water masses (Red Sea Water [RSW] and Antarctic Intermediate Water [AAIW]) as well as in the upper waters (Subtropical Surface Water [STSW] and Indonesian Throughflow Water [ITW]). Through the northern gap, mixing occurs between Arabian Sea High-Salinity Water (ASHSW), ITW and Tropical Surface Water (TSW), while through the southern gap, mixing occurs between STSW and ITW. North Indian Deep Water (NIDW) is present in the region but the plateau appears to have no effect on it.  相似文献   

20.
This study describes the first year round observations of the outflow from Hudson Strait as obtained from a moored array deployed mid-strait from August 2004–2005, and from a high-resolution hydrographic section conducted in September 2005. The outflow has the structure of a buoyant boundary current spread across the sloping topography of its southern edge. The variability in the flow is dominated by the extreme semi-diurnal tides and by vigorous, mostly barotropic, fluctuations over several days. The fresh water export is seasonally concentrated between June and March with a peak in November–December, consistent with the seasonal riverine input and sea-ice melt. It is highly variable on weekly timescales because of synchronous salinity and velocity variations. The estimated volume and liquid fresh water transports during 2004–2005 are, respectively, of 1–1.2 Sv and 78–88 (28–29) mSv relative to a salinity of 34.8 (33). This implies that the Hudson Strait outflow accounts for approximately 15% of the volume and 50% of the fresh water transports of the Labrador Current. This larger than previously estimated contribution is partially due to the recycling, within the Hudson Bay System, of relatively fresh waters that flow into Hudson Strait, along its northern edge. It is speculated that the source of this inflow is the outflow from Davis Strait.  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