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1.
A mooring was deployed east of Mindanao Island at 8°N, 127°3′E from December 2010 to August 2014 to collect direct measurements of the Mindanao Current (MC). The Acoustic Doppler Current Profiler (ADCP) fixed on the main float shows that the MC is a strong and stable southward flow with a standard deviation less than 21 cm/s in the upper 500 m. The core flows between depths of 50 and 100 m with a maximum mean speed of 78 cm/s at 100 m. The seasonal variability of MC varies interannually and is depth-dependent. Although it takes a double-peak structure in the upper 200 m with two maxima in April and June and one minimum in October, the MC velocity has its maximum during boreal summer (June) and a minimum in autumn (September) when a 100-day low-pass filter is applied to remove intraseasonal signals. The semiannual signals are mainly limited between 200 and 350 m. The Asian monsoon intensifies the wind-driven sea-surface height anomaly (SSHA) east of Mindanao Island, and the resulting sharp slope induces meridional flow with large variability. Rossby waves and the boundary effect weaken the contribution of wind, stabilizing the flow of MC. The MC is determined by the zonal gradient of the SSHA rather than the SSHA itself, suggesting a possible inconsistency in seasonality between the Mindanao Eddy (ME) and MC. The semiannual ME signal plays an important role in the seasonal variability of MC.  相似文献   

2.
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.  相似文献   

3.
The characteristics of currents and tidal currents in the Andaman Sea(AS) are studied during the second half of2016 using observed data from a moored acoustic Doppler current profiler(ADCP) deployed at 8.6°N, 95.6°E.During the observation period, the mean flow is 5–10 cm/s and largely southward. The root mean square and kinetic energies of the low and high frequency flows, which are divided by a cutoff period of 5 d, are at the same level, indicating their identical importance to the total current. A power spectrum analysis shows that intraseasonal oscillations, a tidal-related semilunar month signal, a semidiurnal tidal signal and periods of 3–4 d are prominent. The barocliny of an eddy kinetic energy is stronger than the mean kinetic energy, both of which are the strongest on the bottom and the weakest at 70 m depth. Residual currents are largely southward(northward) during the summer(winter) monsoon season. Two striking peaks of the southward flow cause the 80 d period of meridional currents. The first peak is part of a large-scale circulation, which enters the AS through the northern channel and exits through the southern channel, and the second peak is part of a local vortex. The 40 d oscillation of the zonal current is forced by geostrophic variations attributed to local and equatorial remote forcing. The tidal current is dominated by semidiurnal constituents, and among these, M2 and N2 are the top two largest major axes. Moreover, astronomical tidal constituents MM and MSF are also significant. Diurnal constituents are weak and shallow water tides are ignorable. The aims are to introduce the new current data observed in the AS and to provide initial insights for the tidal and residual currents in the Andaman Sea.  相似文献   

4.
In order to quantitatively estimate the volume and property transports between the South China Sea and Indonesian Seas via the Karimata Strait, two trawl-resistant bottom mounts, with ADCPs embedded, were deployed in the strait to measure the velocity profile as part of the South China Sea-Indonesian Seas transport/exchange (SITE) program. A pair of surface and bottom acoustic modems was employed to transfer the measured velocity without recovering the mooring. The advantage and problems of the instruments in this field work are reported and discussed. The field observations confirm the existence of the South China Sea branch of Indonesian throughflow via the Karimata Strait with a stronger southward flow in boreal winter and weaker southward bottom flow in boreal summer, beneath the upper layer northward (reversal) flow. The estimate of the averaged volume, heat and freshwater transports from December 2007 to March 2008 (winter) is (-2.7 ± 1.1) × 10 6 m3/s, (-0.30 ± 0.11) PW, (-0.18 ± 0.07) × 106m3/s and from May to September 2008 (summer) is (1.2 ± 0.6) × 106m3/s, (0.14 ± 0.03) PW, (0.12 ± 0.04) × 106m3/s and for the entire record from December 2007 to October 2008 is (-0.5 ± 1.9) × 10 6 m3/s, (-0.05 ± 0.22) PW, (-0.01 ± 0.15) × 106m3/s (negative/positive represents southward/northward transport), respectively. The existence of southward bottom flow in boreal summer implies that the downward sea surface slope from north to south as found by Fang et al. (2010) for winter is a year-round phenomenon.  相似文献   

5.
The large-scale circulation of the Indian Ocean has several major components. There is a cyclonic gyre in the far southwest with its axis along about 60°S. It extends to the bottom. North of this the Circumpolar Current flows eastward south of 40°S to more than 3000 m. The axis of the great anticyclonic gyre lies along 35°S to 40°S down to about 2000 m. Below there the western end shifts northward and the axis lies along the central and southeast Indian ridges, with southward flow west of the ridges and northward flow on the east side.There is a westward flow along 10°S to 15°S, which includes water from the Pacific, through the Banda Sea. The flow near the equator is eastward down to the depth of the ridge near 73°E. Flow within both the Arabian Sea and Bay of Bengal is cyclonic down to great depth.There is a southward flow along the coast of Africa in the upper 2000 m joining the Circumpolar Current, and a southward flow along the coast of Australia that does not reach the Circumpolar Current.Below 2500 m there is a northward flow from the Circumpolar Current along the east coast of Madagascar and on into the Somali and Arabian basins.  相似文献   

6.
南海北部东沙岛附近的内潮和余流特征   总被引：4，自引：2，他引：2  
采用东沙岛附近的一个长达9个月的锚定潜标的观测资料对南海北部的正压潮、内潮和余流情况进行了分析,得到了当地正压潮和内潮的特征。此处正压潮流以全日潮为主,秋、冬季相对较大,春季相对较小;正压余流受海盆尺度环流和地形的限制,在潜标观测期间的秋、冬、春三季基本以偏西向的正压流为主。内潮同正压潮一样,也以全日分潮为主,潮流椭圆随水深发生旋转,在110—120m附近存在内潮非常弱的一层。斜压余流在2009年2—3月比较异常,这是由于在此其间有一个中尺度涡经过。对此潜标数据采用经验正交函数分解的方法进行分析,发现海流的各个主要EOF模态与内波的垂向模态结构有一定的关联。  相似文献   

7.
王毅  崔凤娟 《海洋与湖沼》2015,46(2):241-247
本文通过分析RAMA印度洋观测浮标系统锚系ADCP实测资料,对赤道中印度洋上层海流季节变化进行了研究。研究结果表明,0°,80.5°E纬向流垂向剖面呈现上150m层一致的东向流,而经向流在100m以浅呈现表层向北次表层向南的翻转流结构。赤道中印度洋上层纬向流季节信号被半年周期的东向射流Wyrtki Jets(WJs)所控制。WJs发生于季风方向转换的季节,4—5月份较弱,10—11月份较强。赤道中印度洋上层经向流年周期信号显著。北半球夏季与冬季分别出现风应力旋度驱动的Sverdrup南向流与北向流。本文结论为赤道中印度洋上层环流季节变化特征的研究提供了观测角度的支持。  相似文献   

8.
Short-term flow fluctuations in the southern central part of Onagawa Bay were examined using long-term mooring and hydrographic data observed during the period from May 2013 to April 2014. The short-term flow fluctuations were dominant in the periodic bands of 15–27 days and shorter than 10 days. The principal and minor components of these flow fluctuations were respectively along and across the local isobaths, which are almost parallel in the north direction. The northward flow fluctuations along the local isobaths were correlated with the northeastward wind fluctuations in both periodic bands, and these correlations were more evident from fall to winter. On the basis of these results, the northward flows are regarded as wind-induced barotropic coastal jets. On other hand, the eastward flow fluctuations across the local isobaths were related to inflow and outflow via the bay mouth or the Izushima Channel. Inflow and outflow with reverse flow at lower depths formed in summer, but those with vertically uniform flow tended to form in winter. The main summertime inflow and outflow were driven by horizontal gradients in density. These permit us to regard the main summertime inflow and outflow as gravitational circulation. Also, the summertime inflow can be intermittently caused by internal waves.  相似文献   

9.
本文利用在西太平洋牛郎海山布放的两套锚系潜标获取的长时间海流观测数据,分析了深海的海洋动力环境特征,着重阐释了该海域海流的全水深垂向结构及其低频变化特征。结果表明:（1）年平均海流及其变化幅度均在上层最大、中层和深层次之、中深层最小;（2）年平均上,150 m以浅的海流为东向的副热带逆流,150 m以深和中层为西向流;山顶处的近底层海流为较稳定的弱南向流,山底处的近底层海流为西南向流;（3）在山顶和山底,各深度层次的海流在全年均表现出100 d左右的振荡周期;在2 000 m以浅,各深度层次的海流振荡的位相基本一致,振荡幅度在表层最强、随深度的增加而减小;在2 000 m以深,海流变化的位相与2 000 m以浅相反,振荡幅度在4 000 m最强。  相似文献   

10.
We conducted 1-year-long mooring observations four times below 2000?m, slightly south of the equator (2°39?? to 4°35??S) at 162°E in the Melanesian Basin in order to detect the southward deep western boundary return current crossing the equator. Contrary to our initial expectation of the deep flow scheme in the equatorial western boundary region, the observed results indicated a fairly complicated flow configuration. We analyzed the results with the help of a high-resolution model simulation. The ensemble average of the horizontal flow at each level near the deep western boundary indicates a significant westward flow at 2000 and 2250?m, with an insignificant southward component at 2500 and 2750?m. The annual mean meridional transports are very small (>1?Sv) and insignificant, with an ensemble-averaged value of 0.3?Sv (southward) ±0.4?Sv at most. Combining this with high-resolution model results, it is deduced that the southward transport of the deep western boundary current (DWBC) leaving the equator may be smaller than those obtained by low-resolution models, because of trapping of its fairly large fraction in the equatorial zone. Annual-scale flow patterns are classified into several categories, mainly based on the meridional-flow dominating or the zonal-flow dominating pattern. A case of the meridional-flow dominating patterns may possibly capture an annual-scale variability of DWBC, because its meridional transport variation, though somewhat weak, is consistent with that simulated. The zonal-flow dominating regime includes two types: long-lasting, almost steady westward flows and long-term zonal flow oscillations. The former seems to comprise well-known zonally elongated and meridionally narrow structures of the zonal flow beneath the thermocline in the equatorial region. The ensemble-averaged flow mentioned above is dominated by this type at the upper two levels 2000 and 2250?m, with total westward transport of 1.6?±?0.7?Sv. The latter type seems to be a manifestation of the vertically propagating equatorial annual Rossby waves.  相似文献   

11.
One year records of four current meters moored at two sites off Sanriku (39°26′ N, 142°45′ E and 143°E) have been analyzed. Mean currents flowed southward to southwestward with velocity 2.5–7.8 cm s−1. The geostrophic velocity appeared to be surface-intensified, and the flows at 500 m depth have a relationship with the 100 m depth temperature distribution, suggesting the influence of the upper layer flows. At a depth of 1500 m and 2500 m, southward to southwestward flows are thought to be a part of the current flowing southward on the western flank of the Japan Trench. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

12.
利用旋转谱分析、调和分析和低通滤波的方法,对1987年8月至1988年1月南海北部东沙附近陆架坡折带处定点海流观测资料进行分析,研究了该区域定常余流、潮流和低频流的特征。各观测层次定常余流基本为西向流,垂向呈现较强的正压性。潮流以日分潮和半日分潮为主,呈顺时针方向旋转,全日潮流椭圆长轴普遍大于半日潮流,冬季K1分潮振幅在近底层明显增大,海流在中间层存在明显的惯性振荡。从能量角度分析,剩余流占海流总能量比例较大,定常余流能量主要存在于沿岸线方向,而垂直于岸线方向的能量主要由潮流和剩余流构成。低频流存在显著的季节变化,1988年1月呈现明显的顺时针旋转形态。冬季海表面风应力与次表层低频流有较强的相关性。结合OFES(Ocean General Circulation Model for the Earth Simulator)模拟结果,利用动量平衡分析的方法探究了动量方程中各项对低频流的贡献以及1988年1月次表层出现北向流的动力机制。冬季低频流具有较强的地转流特征,垂向分布受海水层化影响;东北风松弛和反气旋涡的联合作用是次表层出现偏北向流动的主要原因。  相似文献   

13.
The ocean general circulation model for the earth simulator(OFES) products is applied to estimate the transports of the Mindanao Current(MC) and the Mindanao undercurrent(MUC) and explore the relation between them on seasonal scale. In general, the MUC is composed of the lower part of the Southern Pacific Tropical Water(SPTW)and Antarctic Intermediate Water(AAIW). While the deep northward core below 1 500 m is regarded as a portion of MUC. Both salinity and potential density restrictions become more reasonable to estimate the transports of MC/MUC as the properties of water mass having been taken into consideration. The climatological annual mean transport of MC is(37.4±5.81)×10~6 m~3/s while that of MUC is(23.92±6.47)×10~6 m~3/s integrated between 26.5 σ_θ and 27.7 σ_θ, and(17.53±5.45)×10~6 m~3/s integrated between 26.5 σ_θ and 27.5 σ_θ in the OFES. The variations of MC and MUC have good positive correlation with each other on the seasonal scale: The MC is stronger in spring and weaker in fall, which corresponds well with the MUC, and the correlation coefficient of them is 0.67 in the OFES.The same variations are also appeared in hybrid coordinate ocean model(HYCOM) results. Two sensitive experiments based on HYCOM are conducted to explore the relation between MC and MUC. The MUC(26.5σ_θ27.7) is strengthening as the MC increases with the enhancement of zonal wind field. It is shown,however, that the main part of the increasement is the deeper northward high potential density water(HPDW),while the AAIW almost remains stable, SPTW decreases, and vice versa.  相似文献   

14.
The primary purpose of this paper is to describe the seasonal variation of the various currents which comprise the California Current System—the California Current, the California Undercurrent, the Davidson Current and the Southern California Countercurrent—and to investigate qualitatively the dynamical relationships among these currents. Although the majority of information was derived from existing literature, previously unpublished data are introduced to provide direct evidence for the existence of a jet-like Undercurrent over the continental slope off Washington, to illustrate ‘event’-scale fluctuations in the Undercurrent and to investigate the existence of the Undercurrent during the winter season.The existing literature is thoroughly reviewed and synthesized. In addition, and more important, geostrophic velocities are computed along several sections from the Columbia River to Cape San Lazaro from dynamic heights given by (1966), and (1964), and and (1976). From these data and from long-term monthly wind stress data and vertical component of wind stress curl data (denoted curl τ) given by (1977), interesting new conclusions are made. 1. The flow that has been denoted the California Current generally has both an offshore and a nearshore maximum in its alongshore coponent. 2. The seasonal variation of the nearshore region of strong flow appears to be related to the seasonal variation of the alongshore component of wind stress at the coast, τyN, at all latitudes. Curl τ near the coast may also contribute to the seasonal signal, accounting for the lead of maximum current over maximum wind stress from about 40°N northward. Large-scale flow separation and fall countercurrents that of headlands may account for the sudden occurrence of late summer and fall countercurrents that appear as large anomalies from the wind-driven coastal flow south of 40°N. 3. From Cape Mendocino southward a northward mean is imposed on the nearshore current distribution. The mean is largest where curl τ is locally strongest, in particular, off and south of San Francisco and in the California Bight. It may be responsible for the portion of the Davidson Current that occurs off California, for the San Francisco Eddy and for the Southern California Eddy or Countercurrent. When southward wind stress weakens in these regions, the northward mean dominates the flow. Flow separation in the vicinity of headlands may also be responsible for these northward flows. There is some evidence that during periods of northward flow a mean monthly τyN-driven southward current occurs inshore of the mean northward flow. At all latitudes, wind-driven ‘event’-scale fluctuations are expected to be superimposed on the seasonal nearshore flow. 4. The spatial distribution and seasonal variation oftthe offshore region of southward flow appear to be related to the spatial distribution and seasonal variation of curl τ. The seasonal variation of curl τ in these areas, curl τl, is roughly in phase with the seasonal variation of τy near the coast and roughly 180° out of phase with the seasonal variation of curl τ near the coast. Southward flow lags negative curl τ by from two to four months. The offshore region of southward flow is strongest during the summer and early fall. The mean annual location of the maximum flow is at about 250–350 km from shore off Washington and Oregon, and at 430 km off Cape Mendocino, 270 km off Point Conception and 240 km off northern Baja. The offshore branch of the flow bends shoreward near 30°N, which is consistent with the shoreward extension of the region of negative curl τ, so that by Cape San Lazaro (25°N), a single region of strong flow is observed within 200 km of the coast. 5. A third region of strong southward flow occurs at distances exceeding 500 km from the coast. The spatial distribution of this flow appears to be related to the spatial distribution of curl τ. 6. The mean northward flow known as the Davidson Current consists of two regions in which the forcing may be dynamically different—seaward of the continental slope off Washington and Oregon and between Cape Mendocino and Point Conception, the mean monthly northward currents appear to be related to the occurrence of positive curl τ; along the coast of Oregon and Washington the northward currents are not related to the occurrence of positive curl τ but are consistent with forcing by the mean monthly northward wind stress at the coast. 7. A region of southward flow that is continuous with the California Current to the south is generally maintained off Oregon and parts of Washington during the winter. This southward flow appears to separate the northward-flowing Davidson and Alaskan Currents in some time-dependent region south of Vancouver Island. The banded current structure is consistent with the distribution of curl τ, if southward flow is related to negative curl τ. 8. The seasonal progression of the California Undercurrent may be related both to the seasonal variation of the offshore region of strong flow (hence to curl τl) and to the alongshore component of wind stress at the coast. South of Cape Mendocino a northward mean also seems to be superimposed on the flow. This mean may be related to the occurrence of strong positive curl τ near the coast. Velocities at Undercurrent depths have two maxima, one in late summer and one in winter. The slope Undercurrent is indistinguishable, except by location, from the undercurrent that is observed on the Oregon-Washington continental shelf.  相似文献   

15.
The three-dimensional structure and the seasonal variation of the North Pacific meridional overturning circulation (NPMOC) are analyzed based on the Simple Ocean Data Assimilation data and Argo profiling float data.The NPMOC displays a multi-cell structure with four cells in the North Pacific altogether.The TC and the STC are a strong clockwise meridional cell in the low latitude ocean and a weaker clockwise meridional cell between 7°N and 18°N,respectively, while the DTC and the subpolar cell are a weaker ...  相似文献   

16.
The ear-shaped thermal front(ESTF), formed by the convergence of the Yellow Sea Warm Current(YSWC) and the Shandong Coastal Current(SCC), is a very important oceanic phenomenon in the Yellow Sea(YS) in winter. In situ measurements and reanalysis datasets all demonstrate that the ESTF has been weakening during1950s–1990s, and a similar weakening trend is also found in winter monsoon over the YS. Numerical experiments show that the weakening of winter monsoon can induce an anomalous circulation in the YS on multi-decadal timescale with northward anomalous currents along China's coast and southward anomalous currents in the central YS—generally opposite to seasonal mean circulation. The anomalous circulation causes slowdown of the YSWC and the SCC, and thus weakens the ESTF. Since the ESTF plays important roles in regional ocean dynamics and air-sea interactions, its weakening has important implications for regional climate in the YS in winter.  相似文献   

17.
The structure of the annual-mean shallow meridional overturning circulation(SMOC) in the South China Sea(SCS) and the related water movement are investigated,using simple ocean data assimilation(SODA) outputs.The distinct clockwise SMOC is present above 400 m in the SCS on the climatologically annual-mean scale,which consists of downwelling in the northern SCS,a southward subsurface branch supplying upwelling at around 10°N and a northward surface flow,with a strength of about 1×10~6 m~3/s.The formation mechanisms of its branches are studied separately.The zonal component of the annual-mean wind stress is predominantly westward and causes northward Ekman transport above 50 m.The annual-mean Ekman transport across 18°N is about 1.2×10~6 m~3/s.An annual-mean subduction rate is calculated by estimating the net volume flux entering the thermocline from the mixed layer in a Lagrangian framework.An annual subduction rate of about 0.66×10~6m~3/s is obtained between 17° and 20°N,of which 87% is due to vertical pumping and 13% is due to lateral induction.The subduction rate implies that the subdution contributes significantly to the downwelling branch.The pathways of traced parcels released at the base of the February mixed layer show that after subduction water moves southward to as far as 11°N within the western boundary current before returning northward.The velocity field at the base of mixed layer and a meridional velocity section in winter also confirm that the southward flow in the subsurface layer is mainly by strong western boundary currents.Significant upwelling mainly occurs off the Vietnam coast in the southern SCS.An upper bound for the annual-mean net upwelling rate between 10° and 15°N is 0.7×10~6m~3/s,of which a large portion is contributed by summer upwelling,with both the alongshore component of the southwest wind and its offshore increase causing great upwelling.  相似文献   

18.
为了揭示长江口外海域海流的特征及其季节和垂向变化规律,于2006年8月1日-2007年7月31日在长江口外海域（平均水深约46.0m）利用大型浮标进行了1年的分层海流流速流向观测。结果表明：（1）该海域海流为顺时针方向的旋转流,在垂向上流向较一致,季节变化不显著。（2）长江口外海域水平流速总体较大,夏季表层最大流速为128.5cm/s,冬季最大表层流速为105.5cm/s;垂线平均流速相近（差异<8.0 cm/s）,夏季流速最大为47.0cm/s,冬季为40.8cm/s。小潮的平均流速为26.5cm/s,大潮平均流速为小潮的2倍。（3）剖面各层流速垂向差异明显,最大流速出现在表层（春季和冬季）或次表层（夏季和秋季）,最小流速均出现在底层;各层的最大平均流速为57.9cm/s,出现在夏季的18m层。（4）垂线平均余流为7.5~11.3 cm/s,春季最强冬季最弱;春季和冬季各层余流均为东向,夏季和秋季基本为东北向或北向。（5）观测海域海流受长江冲淡水、台湾暖流、季风、潮汐等动力作用的共同制约。  相似文献   

19.
《Coastal Engineering》2005,52(1):93-102
A simplified analytical model for continental shelf wind-driven currents is adopted. The calculated results compare favorably with extensive field measurements from two separate sources. The model is used to hindcast the current climatology on the Israeli continental shelf. The maximum northward/southward alongshore currents at 10-m water depth, with a return period of 100 years, are found to be 1.28 and 0.53 m/s, respectively.  相似文献   

20.
The Mozambique Channel plays a key role in the exchange of surface water masses between the Indian and Atlantic Oceans and forms a topographic barrier for meridional deep and bottom water circulation due to its northward shoaling water depths. New high-resolution bathymetry and sub-bottom profiler data show that due to these topographic constraints a peculiar seafloor morphology has evolved, which exhibits a large variety of current-controlled bedforms. The most spectacular bedforms are giant erosional scours in the southwest, where northward spreading Antarctic Bottom Water is topographically blocked to the north and deflected to the east forming furrows, channels and steep sediment waves along its flow path. Farther north, in the water depth range of North Atlantic Deep Water, the seafloor is strongly shaped by deep-reaching eddies. Steep, upslope migrating sediment waves in the west have formed beneath the southward flow of anticyclonic Mozambique Channel eddies (MCEs). Arcuate bedforms in the middle evolved through an interaction of the northward flow of MCEs with crevasse splays from a breach in the western Zambezi Channel levee. Hummocky bedforms in the east result from an interplay of East Madagascar Current eddies with overspill deposits of the crevasse and Zambezi Channel. All bedforms are draped with sediments indicating that the present-day current velocities are not strong enough to erode sediments. Hence, it can be concluded that the seafloor morphology developed during earlier times, when bottom-current velocities were stronger. Assuming a sedimentation rate of 20 m/Ma and a drape of at least 50 m thickness the bedforms may have developed during the Pliocene Epoch or earlier.  相似文献   

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