Post-glacial persistence of turbiditic activity within the Rhône deep-sea turbidite system (Gulf of Lions,Western Mediterranean): Linking the outer shelf and the basin sedimentary records     

Bernard Dennielou  Laurent Jallet  Nabil Sultan  Gwenael Jouet  Pierre Giresse  Michel Voisset  Serge Berné 《Marine Geology》2009,257(1-4):65-86

Emplacement of post-glacial turbidites is commonly controlled by rapid changes in sea level or by seismicity. On the continental rise of the Gulf of Lions (Western Mediterranean), an aseismic area, we identified turbiditic beds deposited during the rising stage and highstand of sea level. Swath bathymetry, sediment cores, in situ Cone Penetrating Tests (CPTU), heavy mineral associations and radiocarbon dating determined the source, composition, distribution and age of the turbiditic beds. Turbidites are composed of homogeneous to positively graded silts to medium sand with quartz (up to 90%), shell debris and shelfal benthic faunas. Their distribution on the sea floor is very patchy and controlled by abundant inherited erosional bedforms. Their source is found in relict regressive sands at the outershelf. Their deposition occurred just after the onset of the post-glacial sea level rise and the concomitant sediment starvation of the Rhône deep sea turbiditic system until recently. Whilst canyons are fed with sand by strong seasonal hydro-sedimentary dynamics on the outershelf, the emplacement of post-glacial turbidites is not controlled by sea level changes but probably by the periodic flushing of the canyons. Our study revealed that this low energy aseismic margin undergoes significant transport of sand, down to the base of slope, during the sea-level rise and the Holocene highstand.  相似文献   

Weather regimes over Senegal during the summer monsoon season using self-organizing maps and hierarchical ascendant classification. Part II: interannual time scale     

A. K. Guèye  Serge Janicot  A. Niang  S. Sawadogo  Benjamin Sultan  A. Diongue-Niang  S. Thiria 《Climate Dynamics》2012,39(9-10):2251-2272

The aim of this work is to define over the period 1979–2002 the main synoptic weather regimes relevant for understanding the daily variability of rainfall during the summer monsoon season over Senegal. “Interannual” synoptic weather regimes are defined by removing the influence of the mean 1979–2002 seasonal cycle. This is different from Part I where the seasonal evolution of each year was removed, then removing also the contribution of interannual variability. As in Part I, the self-organizing maps approach, a clustering methodology based on non-linear artificial neural network, is combined with a hierarchical ascendant classification to compute these regimes. Nine weather regimes are identified using the mean sea level pressure and 850?hPa wind field as variables. The composite circulation patterns of all these nine weather regimes are very consistent with the associated anomaly patterns of precipitable water, mid-troposphere vertical velocity and rainfall. They are also consistent with the distribution of rainfall extremes. These regimes have been then gathered into different groups. A first group of four regimes is included in an inner circuit and is characterized by a modulation of the semi-permanent trough located along the western coast of West Africa and an opposite modulation on the east. This circuit is important because it associates the two wettest and highly persistent weather regimes over Senegal with the driest and the most persistent one. One derivation of this circuit is highlighted, including the two driest regimes and the most persistent one, what can provide important dry sequences occurrence. An exit of this circuit is characterised by a filling of the Saharan heat low. An entry into the main circuit includes a southward location of the Saharan heat low followed by its deepening. The last weather regime is isolated from the other ones and it has no significant impact on Senegal. It is present in June and September, and missing in July and August, meaning that this is a weather regime more specific of the intermediate seasons than the summer. It is included in a large-scale pattern covering the northern latitudes of Europe. The correspondence between these “interannual” synoptic weather regimes and the “pure” synoptic regimes defined in Part I has been established. By selecting a high statistical significance level for these correspondences, each of five out of nine “interannual” weather regimes has a close correspondence with one “pure” synoptic weather regime, one out of them have links with two “pure” regimes, and the last three regimes have no significant correspondence in terms of “pure” regimes. However when considering more moderate links, two out of these three regimes show a connection with a “pure” regime, and the last one remains isolated. The ensemble of the weather regimes occurrences can explain a significant part of interannual variability of summer rainfall amount over Senegal, especially linked to the driest and the wettest weather regimes occurrences. It is also shown that Senegal rainfall state is very sensitive to a small displacement or deformation of the weather regime patterns.  相似文献   

Monthly variations of net heat flux at the air‐sea interface in coastal waters near Jeddah,Red Sea     

F. Ahmad  S.A.R. Sultan  M.O. Moammar 《大气与海洋》2013,51(2):406-413

Abstract

Based on 16 years of oceanographic and meteorological data the monthly variations of the net heat flux at the air‐sea interface in coastal waters near Jeddah show that the sea gains an average of about 14 ±2 W m^?2 from April to October and loses about 79± 4W m^?2from November to March. The loss of heat during the winter months is not compensated by the gain during the summer months and therefore leads to an annual average deficit of 25 ± 3 Wm^?2. The gain during summer may not favour the formation of a strong seasonal thermocline.  相似文献   

Weather regimes over Senegal during the summer monsoon season using self-organizing maps and hierarchical ascendant classification. Part I: synoptic time scale     

A. K. Gu��ye  Serge Janicot  A. Niang  S. Sawadogo  Benjamin Sultan  A. Diongue-Niang  S. Thiria 《Climate Dynamics》2011,36(1-2):1-18

The aim of this work is to define over the period 1979?C2002 the main synoptic weather regimes relevant for understanding the daily variability of rainfall during the summer monsoon season over Senegal. ??Pure?? synoptic weather regimes are defined by removing the influence of seasonal and interannual time scales, in order to highlight the day by day variability of the atmospheric circulation. The Self-Organizing Maps (SOM) approach, a clustering methodology based on non-linear artificial neural network, is combined with a Hierarchical Ascendant Classification to compute these regimes. Nine weather regimes are identified using the mean sea level pressure and 850?hPa wind field as variables, and gathered into three classes. Two of these weather regimes represent the classical 3?C5-day African easterly waves with a mean wavelength of about 3,000?km. Three others are characterized by a modulation of the semi-permanent trough located along the western coast of West Africa and might be interpreted in terms of the 6?C9-day easterly waves. The last four weather regimes are characterized by a more or less strong north?Csouth dipole of circulation. They can be interpreted as a northward/southward displacement of the Saharan Heat Low for two of them, and a filling/deepening of this depression for the other two. The circulation patterns of all these nine weather regimes are very consistent with the associated anomaly patterns of precipitable water, mid-troposphere vertical velocity, outgoing longwave radiation, and finally rainfall. Rainfall distribution is also highlighted over the southwestern area of Senegal.  相似文献   

Surface currents and equatorial thermocline in a coupled upper ocean-atmosphere GCM     

Kenneth R Sperber  Sultan Hameed  W Gates Lawrence 《Climate Dynamics》1992,7(3):121-131

The Oregon State University coupled upper ocean-atmosphere GCM is evaluated in terms of the simulated winds, ocean currents and thermocline depth variations. Although the zonal wind velocities in the model are underestimated by a factor of about three and the zonal current velocities are underestimated by a factor of about five, the model is seen to qualitatively simulate the major features of the gyral scale currents, and the phases of the seasonal variation of the principal equatorial currents are in reasonable agreement with observations. The simulated tropical currents are dominated by Ekman transport and the eastern boundary currents do not penetrate far enough equatorward, while the western boundary currents do not penetrate far enough poleward. The subtropical trade wind belt and the mid-latitude westerlies are displaced equatorward of observations; hence, the mid-latitude eastward currents, principally the Kuroshio-North Pacific Drift and the Gulf Stream-North Atlantic Current are displaced equatorward. In spite of these shortcomings the surface current simulation of this two-layer upper ocean model is comparable with that of other ocean GCMs of coarse resolution. The coupled model successfully simulates the deepening of the thermocline westward across Pacific as a consequence of the prevailing Walker circulation. The region of most intense simulated surface forcing is located in the western Pacific due to a southwestward displacement of the northeast trade winds relative to observations; hence the equatorial Pacific is dominated by eastward propagation of thermocline depth variations. The excessively strong Ekman divergence and upwelling in the western Pacific cools the local warm pool, while incorrectly simulated westerlies in the eastern Pacific suppress upwelling and inhibit cooling from below. These features reduce the simulated trans-Pacific sea-surface temperature gradient, weakening the Walker circulation and the anomalies associated with the simulated Southern Oscillation. Offprint requests to: KR Sperber  相似文献   

Evaluating subsurface structures and stratigraphic units using 2D electrical and magnetic data at the area north Greater Cairo,Egypt     

S.A. Sultan  F.A.M. Santos 《International Journal of Applied Earth Observation and Geoinformation》2008

2D dipole–dipole resistivity data and ground magnetic survey are used in combination with available data from boreholes and surface geology to detect subsurface structures and stratigraphic units and to study the ability of the site area (located at north Grater Cairo) for a building construction.  相似文献   

Extracting spatial patterns in bicycle routes from crowdsourced data   总被引：1，自引：0，他引：1       下载免费PDF全文

Jody Sultan  Gev Ben‐Haim  Jan‐Henrik Haunert  Sagi Dalyot 《Transactions in GIS》2017,21(6):1321-1340

Much is done nowadays to provide cyclists with safe and sustainable road infrastructure. Its development requires the investigation of road usage and interactions between traffic commuters. This article is focused on exploiting crowdsourced user‐generated data, namely GPS trajectories collected by cyclists and road network infrastructure generated by citizens, to extract and analyze spatial patterns and road‐type use of cyclists in urban environments. Since user‐generated data shows data‐deficiencies, we introduce tailored spatial data‐handling processes for which several algorithms are developed and implemented. These include data filtering and segmentation, map‐matching and spatial arrangement of GPS trajectories with the road network. A spatial analysis and a characterization of road‐type use are then carried out to investigate and identify specific spatial patterns of cycle routes. The proposed analysis was applied to the cities of Amsterdam (The Netherlands) and Osnabrück (Germany), proving its feasibility and reliability in mining road‐type use and extracting pattern information and preferences. This information can help users who wish to explore friendlier and more interesting cycle patterns, based on collective usage, as well as city planners and transportation experts wishing to pinpoint areas most in need of further development and planning.  相似文献   

Marine Bioactive Steryl Esters from the Red Sea Black Coral Antipathes dichotoma     

Walied M. Alarif  Ahmed Abdel‐lateff  Sultan S. AL‐lihaibi  Seif‐Eldin N. Ayyad  Farid A. Badria  Abdulmohsin A. Alsofyani  Zeinab S. Abou‐Elnaga 《洁净——土壤、空气、水》2013,41(11):1116-1121

Two new marine steryl hexadecanoates, 3β‐hexadecanoylcholest‐5‐en‐7‐one ( 1 ) and 3β‐hexadecanoylcholest‐5‐en‐7β‐ol ( 2 ), along with seven known compounds, cholest‐5‐en‐3β‐yl‐formate ( 3 ), thymidine ( 4 ), indole‐3‐carboxaldehyde ( 5 ), 3β‐hydroxycholest‐5‐en‐7‐one ( 6 ), cholesterol ( 7 ), 22‐dehydrocholestrol ( 8 ), and 24‐methylenecholesterol ( 9 ), were isolated from the anthozoan black coral, Antipathes dichotoma. The structures of all isolated compounds were determined by interpretation of their spectral data 1D (¹H, ¹³C and DEPT) and 2D (COSY, HSQC and HMBC) NMR, UV, IR, and MS. Compounds 1 – 5 were evaluated for their anticancer activities, employing four cancer panels; HepG2, WI 38, VERO, and MCF‐7. All tested compounds, except 4 , showed moderate activities. Compound 4 exhibited significant anticancer activity against VERO and MCF‐7, with IC₅₀ 20.5 and 20.2 µg/mL, respectively.  相似文献   

Remote Sensing and GIS based groundwater potential mapping for sustainable water resource management of Lidder catchment in Kashmir Valley,India     

Mohammad Imran Malik  M. Sultan Bhat  Shahnaz Ahmad Najar 《Journal of the Geological Society of India》2016,87(6):716-726

The valley of Kashmir is blessed with abundant water resources. However, high population growth and concentration of population at favorable locations have resulted in increased demand for water. The problem is further aggravated in Lidder catchment where unplanned tourism development has resulted in deterioration of water quality. Multi-Criteria Evaluation (MCE) approach is adopted using IRS P6 LISS III satellite data 2010, geological map published by Geological Survey of India, toposheets prepared by Survey of India, 1961 and field observation. Seven thematic layers (slope, lineament density, drainage density, soil, geology, geomorphology and land use land cover) are generated in GIS environment and weighted according to their relative relevance to groundwater occurrence. Knowledge-based weights and ranks are normalized, and a weighted linear combination technique is adopted to determine the groundwater potential (GWP). The catchment is divided into five zones of very high, high, medium, low and very low GWP. The results show that 50.22% of the total catchment area, which is uninhabited, has very low GWP. However, the densely populated southern part of the catchment has moderate to very high GWP. The study demonstrates that MCE using remote sensing and GIS technology could be efficiently employed as a very useful tool for the assessment and management of groundwater resources especially in regions where data is poor.  相似文献   

Precursors of Copepod Abundance in the Gulf of Maine in Atmospheric Centers of Action and Sea Surface Temperature     

Sergey Piontkovski  Sultan Hameed 《Journal of Atmospheric & Ocean Science》2002,8(4):283-291

Interannual variations of total copepod abundance in the Gulf of Maine (1961-1991) are analyzed and related to the semi-permanent atmospheric pressure systems: Icelandic Low (IL) and the Azores High (AH). These centers of action dominate atmospheric and oceanic circulation in the North Atlantic. Cross-correlation analysis of zooplankton, sea surface temperature (SST) and the atmospheric characteristics have revealed different (from one to three years) time lags between the above characteristics. A multiple stepwise regression analysis gave a correlation value of 0.7 between observed and predicted interannual changes of total copepod abundance. A discussion is included of possible mechanisms that may contribute to the dynamic links that transfer atmospheric variation into observed changes in zooplankton abundance.  相似文献