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1.
The currents in the central part of the Drake Passage are investigated by analyzing the CTD and SADCP data over the section
across the Drake Passage occupied in November 2010 and satellite altimetry data. All eight of the jets of the Antarctic Circumpolar
Current, which are currently identidifed, were resolved by the section. The velocities and water transports of these jets
are estimated. Three synoptic scale eddies with different vertical structures were revealed; hypotheses on the physical nature
of these eddies are discussed. 相似文献
2.
G. G. Panteleev M. N. Koshlyakov E. G. Morozov R. Yu. Tarakanov A. Yu. Goldin A. Yu. Shcherbina M. Ikeda 《Oceanology》2006,46(6):772-783
Computation of ocean currents in the Drake Passage is carried out with variational assimilation of the data of the hydrographical section across the Drake Passage carried out on December 11–15, 2003, and other data. A stream-eddy structure of the easterly Antarctic Circumpolar Current and a westerly current on the Antarctic Slope are obtained. Water transports by the different current field components and the integral transport across the Drake Passage are estimated. The necessity of direct current measurements in the Drake Passage for a correct estimate of the transport is confirmed. 相似文献
3.
The currents in the Drake Passage are studied from the ADCP and CTD data acquired in a section across the Drake Passage in October-November of 2011 and from the satellite altimeter data. A complicated pattern of currents including eight jets of the Antarctic Circumpolar Current (ACC) and a system of slope and abyssal currents was found. The most interesting result is the discovery of several cyclonic and anticyclonic mesoscale eddies confined to the abyss. Some reasons explaining the generation of such eddies by the meandering of the ACC jets in the upper ocean layer are presented. 相似文献
4.
《Deep Sea Research Part I: Oceanographic Research Papers》2007,54(11):1972-1984
The Southern Ocean hosts significant topographic mixing that might be associated with internal tides. Tidal signals are evident in bottom temperature at 1000 m in Drake Passage, suggesting that internal tides with an amplitude of between ∼20 and 200 m may be present. Various necessary conditions for internal tide generation show that the steep topography in and around Drake Passage can initiate internal tides, and recent global tide models have suggested this region to generate very large interface displacements. Here, we present an attempt to detect internal tides in Drake Passage. During the last 10 years, combinations of bottom pressure recorders and inverted echo sounders have been deployed in the region. The bottom pressure recorders measure predominantly the barotropic tide; the inverted echo sounders measure travel time from sea bed to sea surface and therefore are influenced both by sea level (barotropic tide) and internal sound speed (internal tide). By subtracting one from the other, the internal tide should be detectable. Although the technique works successfully around Hawaii, it does not prove the existence of large internal tides in Drake Passage. The detectability of the internal tidal signal in Drake Passage is investigated using a six-layer one-dimensional model to simulate the bottom pressure and travel time signals of a semi-diurnal tide. The temperature and salinity stratification in Drake Passage is sufficiently weak that large vertical excursions are necessary to produce a signal in travel time detectable above the noise in Drake Passage. An internal tide of at least 70 or 20 m in northern and southern Drake Passage, respectively, would be detected. The fact that these are, perhaps surprisingly, not detected by the combination of bottom pressure and travel time, constrains the internal tides in Drake Passage to be ∼20 m in southern Drake Passage, and between 20 and 70 m in northern Drake Passage. The model also predicts that satellite altimetry would not be able to detect internal tides in Drake Passage, but would in the Brazil Basin and Hawaii regions. 相似文献
5.
Koshlyakov M. N. Repina I. A. Savchenko D. S. Tarakanov R. Y. Taroyan V. K. 《Oceanology》2019,59(2):171-181
Oceanology - Satellite altimeter observation data collected over 22 years are used to analyze the structure and variability of mesoscale fluctuations of ocean currents in the Drake Passage and... 相似文献
6.
The Western Drake Passage current system is investigated using the CTD, LADCP, and SADCP data of the cross Drake section carried
out in January 2010. A complicated current structure consisting of the six Antarctic Circumpolar Current (ACC) jets as well
as the system of slope and abyssal currents was revealed. The most interesting result is the identification of the abyssal
quasi-geostrophic spurts in the northern part that probably are generated by abyssal eddy fragments, which are an imperative
part of the meandering ACC. 相似文献
7.
The Southern Ocean plays an important role in the global overturning circulation as a significant proportion of deep water is converted into intermediate and deeper water masses in this region. Recently, a secular trend has been reported in wind stress around the Southern Ocean and it is thought theoretically that the strength of the ACC is closely related to wind stress, so one consequence should be a corresponding increase in ACC transport and hence changes in the rate of the global overturning. There are no long-term data sets of ACC transport and so we must examine other data that may also respond to changing wind stress. Here we calculate surface currents in Drake Passage every seven days over 11.25 years from 1992 to 2004. We combine surface velocity anomalies calculated from satellite altimeter sea surface heights with measured surface currents. Since 1992, the UK has regularly occupied WOCE hydrographic section SR1b across the ACC in Drake Passage. From seven hydrographic sections surface currents are estimated by referencing relative geostrophic velocities from CTD sections with current measurements made by shipboard and lowered acoustic Doppler current profilers. Combining the seven estimates of surface currents with the altimeter data reduces bias in the estimates of average currents over time through Drake Passage and we show that surface current anomalies estimated by satellite and in situ observations are in good agreement. The strongest surface currents are found in the Subantarctic and Polar Fronts with average speeds of 50 cm/s and 35 cm/s, respectively and are inversely correlated, so that maximum westward flow in one corresponds to minimum westward flow in the other. The average cross-sectional weighted surface velocity from 1992 to 2004 is 16.7 ± 0.2 cm/s. A spectral analysis of the average surface current has only weakly increasing energy at higher frequencies and there is no dominant mode of variability. The standard deviation of the seven day currents is 0.68 cm/s and a running 12 month average has only a slightly smaller standard deviation of 0.52 ± 0.16 cm/s. The southern annular mode (SAM) measures the circumpolar average of wind stress and like the surface currents its spectrum has slightly increased energy at frequencies greater than 1 cpy. A cospectral analysis of these, averaging cospectra of five slightly overlapping 36 month segments improve statistical reliability, suggests that there is coherence between them at 1 cpy with the currents leading changes in the Southern annular mode. We conclude that the SAM and average Drake Passage surface currents are weakly correlated with no dominant co-varying modes, and hence predicting Southern Ocean transport variability from the SAM is not likely to give significant results and that secular trends in surface currents are likely to be masked by weekly and interannual variability. 相似文献
8.
The currents within the junction of the Shackleton and West-Scotia ridges in the central part of the Drake Passage are studied
using the data of the hydrographic survey carried out in October–November of 2008. The absolute geostrophic currents were
computed by matching the CTD and LADCP data. As a result, the complicated system of deep currents conditioned by the ocean
bottom’s topography was revealed and described. A new path of propagation of the Antarctic Bottom Water has been revealed. 相似文献
9.
R. Yu. Tarakanov 《Oceanology》2012,52(2):157-170
It is shown on the basis of the data of the Russian Academy of Sciences expeditions in 2003–2010, the historical CTD database,
the WOCE climatology, and the satellite altimetry that the area of the Scotia Sea and the Drake Passage is even a greater
significant orographic barrier for the eastward Antarctic Circumpolar Current (ACC) than was previously thought. It is the
current concept that this barrier is the most important for the ACC; it consists of three obstacles: the Hero Ridge with the
Phoenix Rift, the Shackleton Ridge, and the North Scotia Ridge with the relatively shallow eastern part of the Scotia Sea.
Despite the fact that all three obstacles are permeable for the layer of the Circumpolar Bottom Water (CBW; 28.16 < γ
n
< 28.26) being considered the lower part of the circumpolar water, the circulation in this layer throughout the Scotia Sea
and the Drake Passage quite substantially differs from the transfer by the surface-intensified ACC jets. Herewith, the upper
CBW boundary is the lower limit of the circumpolar coverage of the ACC jets. This result is confirmed by the near zero estimate
of the total CBW transport according to the three series of the LADCP measurements on the sections across the Drake Passage.
It is shown that the transformation (cooling and freshening) of the CBW layer, which occurs owing to the flow of the ACC over
the Shackleton Ridge, is associated with the shape and location of the ridge in the Drake Passage. The high southern part
of this ridge is a partially permeable screen for the eastward CBW transport behind which the colder and fresher waters of
the Weddell Sea and the Bransfield Strait of the same density range as the CBW penetrate into the ACC zone. The partial permeability
of the Shackleton Ridge for the CBW layer leads to the salinization of this layer on the eastern side of the ridge and to
the CBW’s freshening on the western side of this ridge, which is observed across the entire Drake Passage. 相似文献
10.
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
11.
Ju. V. Artamonov A. V. Fedirko E. A. Skripaleva 《Izvestiya Atmospheric and Oceanic Physics》2016,52(9):1051-1063
Based on the satellite altimetry dataset of sea level anomalies, the climatic hydrological database World Ocean Atlas-2009, ocean reanalysis ECMWF ORA-S3, and wind velocity components from NCEP/NCAR reanalysis, the interannual variability of Antarctic Circumpolar Current (ACC) transport in the ocean upper layer is investigated for the period 1959–2008, and estimations of correlative connections between ACC transport and wind velocity components are performed. It has been revealed that the maximum (by absolute value) linear trends of ACC transport over the last 50 years are observed in the date-line region, in the Western and Eastern Atlantic and the western part of the Indian Ocean. The greatest increase in wind velocity for this period for the zonal component is observed in Drake Passage, at Greenwich meridian, in the Indian Ocean near 90° E, and in the date-line region; for the meridional component, it is in the Western and Eastern Pacific, in Drake Passage, and to the south of Africa. It has been shown that the basic energy-carrying frequencies of interannual variability of ACC transport and wind velocity components, as well as their correlative connections, correspond to the periods of basic large-scale modes of atmospheric circulation: multidecadal and interdecadal oscillations, Antarctic Circumpolar Wave, Southern Annual Mode, and Southern Oscillation. A significant influence of the wind field on the interannual variability of ACC transport is observed in the Western Pacific (140° E–160° W) and Eastern Pacific; Drake Passage and Western Atlantic (90°–30° W); in the Eastern Atlantic and Western Indian Ocean (10°–70° E). It has been shown in the Pacific Ocean that the ACC transport responds to changes of the meridional wind more promptly than to changes of the zonal wind. 相似文献
12.
Currents in the Drake Passage are studied using the data of a hydrographic section along the Shackleton Transverse Ridge observed in November 2007. The distribution of the velocity component normal to the section was computed by two methods: (a) directly on the basis of the lowered acoustic Doppler current profiler (LADCP) data; (b) by the calculation of geostrophic currents based on the CTD data with estimating the depth averaged velocity on the basis of the LADCP data. The main results of the research are the relatively low estimated value of the Antarctic Circumpolar Current (ACC) transport, which accounts for 65–70% of the ACC transports in December 2003 and November 2005, and the confirmation of the existence of several abyssal currents confined to the deep passages of the bottom topography. 相似文献
13.
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14.
Seismostratigraphic analysis of the Transkei Basin: A history of deep sea current controlled sedimentation 总被引：1，自引：0，他引：1
The Earth's climate is controlled by various factors, with large scale ocean currents playing a significant role. In particular, the global thermohaline circulation of water masses like the Antarctic Bottom Water (AABW), or the North Atlantic Deep Water (NADW), is a global motor for maintaining the exchange of water masses. The AABW and NADW have met and interacted off South Africa since Oligocene times. Here, the narrow deep Agulhas Passage gateway, located between South Africa and the submarine Agulhas Plateau, constrains bottom water exchange between the southeast Atlantic and the southwest Indian Ocean. A seismostratigraphic analysis of sedimentary structures in the Transkei Basin, which opens up at the eastern end of the Agulhas Passage, was carried out, to reconstruct the palaeocurrents off South Africa. The analysis of newly collected high resolution seismic reflection data showed the effect of large scale current deposition. There are at least 5 major sedimentary phases to observe, some of which seem to be influenced by NADW and AABW. The first stage represents ongoing deep sea sedimentation from middle Cretaceous to middle Tertiary times. Later stages are separated by discordances, which represent the onset of AABW and NADW, among others, triggered by the opening of the Drake Passage gateway ( 35 Ma) and the closure of the Isthmus of Panama ( 3 Ma). We found two large drift bodies located one above the other. Corresponding to their shape and position, the older drift is inferred to have been deposited by currents flowing in a north–southerly direction, whereas the younger drift lies perpendicular to it and seems to be built up by west–east flowing currents. 相似文献
15.
We study the energy exchange between jets of the Antarctic Circumpolar Current (ACC) and synoptic eddies generated by them in the surface layer of the ocean in the Drake Passage and Scotia Sea based on 22-year-long satellite altimetry time series from the French CLS Agency (DT Global–MADT–Upd product, http://www.aviso.altimetry.fr) under the assumption, based on observations, that each of the jets is confined between two fixed contour lines of the absolute dynamic topography of the ocean. We calculate and analyze the 22-year evolution of the kinetic energy of each ACC jet and cyclonic and anticyclonic eddies generated by it. We demonstrate the fundamental dependence of fluctuations in jet energy on the phase of their meander and eddy formation, as well as their back absorption by jets. We calculate the mean and extreme energetic characteristics of jets and eddies and compare the jets in terms of the intensity of the generated eddies. 相似文献
16.
Yu. V. Artamonov N. P. Bulgakov P. D. Lomakin E. A. Skripaleva 《Physical Oceanography》2004,14(6):377-387
On the basis of the many-year monthly average thermohaline data of the oceanographic array, we study some regularities of the seasonal cycle in the fields of temperature, salinity, and the characteristics of water masses in the Drake Passage. We obtain and analyze the amplitude and phase parameters of seasonal oscillations of the investigated quantities. By using the volumetric statistical T, S-analysis, we deduce quantitative estimates of the annual variations of the volumes of main water masses in the Drake Passage. Possible mechanisms responsible for the phenomena observed in this region are discussed.__________Translated from Morskoi Gidrofizicheskii Zhurnal, No. 6, pp. 62–73, November–December, 2004. 相似文献
17.
Ho Il Yoon Kyu-Cheul Yoo Young-Suk Bak Yong Il Lee Jae Il Lee 《Geo-Marine Letters》2009,29(5):309-320
A deep-sea sediment core (GC98-06) from the southernmost Drake Passage, West Antarctica, shows late Quaternary depositional
environments distinctly different from sedimentary drifts commonly found along the southwestern Pacific margin of the Drake
Passage. The chronology of the core has been inferred using geochemical tracers of paleoproductivity and diatom biostratigraphy,
and represents the paleoceanographic conditions in a continental rise setting during the last 150,000 years. Three dominant
sediment types associated with distinct sedimentary processes have been identified using textural/compositional analyses:
(1) hemipelagic mud (interglacial sediments) deposited from pelagic settling of bioclasts, meltwater plumes, and ice-rafted
detritus; (2) terrigenous mud (glacial sediments) delivered by turbid meltwater plumes; and (3) massive muds marking the boundaries
from interglacial to glacial periods. The succession of the sedimentary facies in core GC98-06 is interpreted to reflect temporal
changes in environmental conditions prevailing on the continental rise of the southern Drake Passage in the course of successive
climatic stages over the last 150 ka: from the bottom upward, these are glacial, interglacial, glaciation, glacial, and interglacial
episodes. Variability in sediment flux and diatom abundance seem to have been related to changes in glacial advance, sea-ice
extent, and specific sedimentary environments, collectively influenced by mid- to late Quaternary climatic changes. 相似文献
18.
《Deep Sea Research Part I: Oceanographic Research Papers》2002,49(4):681-705
An unprecedented high-quality, quasi-synoptic hydrographic data set collected during the ALBATROSS cruise along the rim of the Scotia Sea is examined to describe the pathways of the deep water masses flowing through the region, and to quantify changes in their properties as they cross the sea. Owing to sparse sampling of the northern and southern boundaries of the basin, the modification and pathways of deep water masses in the Scotia Sea had remained poorly documented despite their global significance.Weddell Sea Deep Water (WSDW) of two distinct types is observed spilling over the South Scotia Ridge to the west and east of the western edge of the Orkney Passage. The colder and fresher type in the west, recently ventilated in the northern Antarctic Peninsula, flows westward to Drake Passage along the southern margin of the Scotia Sea while mixing intensely with eastward-flowing Circumpolar Deep Water (CDW) of the antarctic circumpolar current (ACC). Although a small fraction of the other WSDW type also spreads westward to Drake Passage, the greater part escapes the Scotia Sea eastward through the Georgia Passage and flows into the Malvinas Chasm via a deep gap northeast of South Georgia. A more saline WSDW variety from the South Sandwich Trench may leak into the eastern Scotia Sea through Georgia Passage, but mainly flows around the Northeast Georgia Rise to the northern Georgia Basin.In Drake Passage, the inflowing CDW displays a previously unreported bimodal property distribution, with CDW at the Subantarctic Front receiving a contribution of deep water from the subtropical Pacific. This bimodality is eroded away in the Scotia Sea by vigorous mixing with WSDW and CDW from the Weddell Gyre. The extent of ventilation follows a zonation that can be related to the CDW pathways and the frontal anatomy of the ACC. Between the Southern Boundary of the ACC and the Southern ACC Front, CDW cools by 0.15°C and freshens by 0.015 along isopycnals. The body of CDW in the region of the Polar Front splits after overflowing the North Scotia Ridge, with a fraction following the front south of the Falkland Plateau and another spilling over the plateau near 49.5°W. Its cooling (by 0.07°C) and freshening (by 0.008) in crossing the Scotia Sea is counteracted locally by NADW entraining southward near the Maurice Ewing Bank. CDW also overflows the North Scotia Ridge by following the Subantarctic Front through a passage just east of Burdwood Bank, and spills over the Falkland Plateau near 53°W with decreased potential temperature (by 0.03°C) and salinity (by 0.004). As a result of ventilation by Weddell Sea waters, the signature of the Southeast Pacific Deep Water (SPDW) fraction of CDW is largely erased in the Scotia Sea. A modified form of SPDW is detected escaping the sea via two distinct routes only: following the Southern ACC Front through Georgia Passage; and skirting the eastern end of the Falkland Plateau after flowing through Shag Rocks Passage. 相似文献
19.
Schemes of surface flows near northwestern Kamchatka are shown, compiled from in situ observation data, numerical-model-derived data, satellite altimetry measurement data, and results calculated by the dynamic method. The flow characteristics obtained by various methods are compared. No statistically significant linear dependence of the velocities of absolute and geostrophic currents were detected. A linear dependence was observed between the directions of geostrophic flows calculated by the standard dynamic method and from satellite altimetry data, as well as between directions measured by the Argonaut MD and the calculated model. We have estimated the fraction of the ageostrophic component in currents. According to geostrophic current calculations by different methods, it ranged from 86 to 93%. A significant limitation of this data is the difficulty of their interpretation. They may not always give a perfect representation of stable water circulation in the studied area under. 相似文献
20.
Oceanology - The research program of the dynamics and ecosystem of the Drake Passage and Scotia Sea is scientifically substantiated. Measurements will be carried out by the interdepartmental... 相似文献