ENSO related modulation of coastal upwelling in the eastern Atlantic   总被引：1，自引：0，他引：1  

Claude Roy  Chris Reason   《Progress in Oceanography》2001,49(1-4)

An index of ENSO in the Pacific during early boreal winter is shown to account for a significant part of the variability of coastal SST anomalies measured a few months later within the wind driven West African coastal upwelling region from 10°N to 26°N. This teleconnection is thought to result from an atmospheric bridge between the Pacific and Atlantic oceans, leading to warm (cold) ENSO events being associated with a relaxation (intensification) of the Atlantic trade winds and of the wind-induced coastal upwelling. This ENSO related modulation of the wind-driven coastal upwelling appears to contribute to the connection observed at the basin-scale between ENSO and SST in the north Atlantic. The ability to use this teleconnection to give warnings of large changes in the West African upwelling several months in advance is successfully tested using data from the 1998 and 1999 ENSO events.  相似文献   

The petroleum evaluation of a tectonically complex area: The western margin of the Southeast Basin (France)     

A. Mascle  R. Vially  E. Deville  B. Biju-Duval  J.P. Roy 《Marine and Petroleum Geology》1996,13(8):941-961

The Southeast Basin of France is the thickest onshore French sedimentary basin which contains locally as much as 10 km of Mesozoic-Cenozoic sediment. Basin development occurred in several stages between late Carboniferous and late Cretaceous times. Partial tectonic inversion took place during two compressive events, the so-called ‘Pyrenean’ and ‘Alpine’ phases of late Cretaceous-early Tertiary and late Tertiary ages respectively. They are separated by an intervening stretching event of Oligocene age, which further south resulted in the opening of the western Mediterranean oceanic basin. As a result of this complex tectonic history, structural traps were difficult to image on the seismic data shot during the first phase of exploration prior to 1980. Oil and gas natural seeps, and shows in several wells, indicate that some petroleum systems are, or have been active, at least in some places.The present erosional western margin of the basin is more or less superimposed on the initial Triassic-Jurassic margin. Margin subsidence and Tertiary inversion are discussed using regional sections on which the polyphase history of the entire basin is well shown. These sections are located on three major segments where the Mesozoic margin is either partly preserved (Ardèche), or has been partly inverted in late Tertiary times (Vercors-Chartreuse), or has been completely inverted in early Tertiary times (Corbières-eastern Pyrenees). 1-D ‘Genex’ basin modelling on the Ardèche segment, and 2-D ‘Thrustpack’ structural-maturity modelling in the Vercors-Chartreuse segment are used to further assess the remaining petroleum plays.  相似文献   

Facies recognition of some Tertiary coals applied to prediction of oil source rock occurrence     

S. Thompson  R.J. Morley  P.C. Barnard  B.S. Cooper 《Marine and Petroleum Geology》1985,2(4):288-297

Coals are oil source rocks in many of the Tertiary basins of Southeast Asia. The precursors of these hydrogen rich and oxygen poor coals are coastal plain peats which have mainly developed in an everwet and tropical climate. In these environments water flow and reworking can concentrate liptinitic kerogen in preference to vitrinitic kerogen. The distribution, petrography and chemistry of the coaly Miocene source rocks present in the Kutai Basin are described. The recognition of environmental controls on the accumulation of potentially oil-prone coals and coaly shales in deltaic environments is an aid to predictive source bed recognition in petroleum exploration. Comments on the environment of deposition of coaly sediments in the basins of the Norwegian Sea are discussed with reference to their possible oil and/or gas sourcing potential. The Triassic - Jurassic coals of the Haltenbanken area may become more oil-prone towards the delta margins, and facies mapping could aid oil exploration in this area.  相似文献   

Long-term effects of tributyltin compounds on the baltic amphipod, Gammarus oceanicus     

Roy Laughlin  Karin Nordlund  Olof Lindn 《Marine environmental research》1984,12(4):243-271

Amphipod larvae, Gammarus oceanicus, were exposed for 8 weeks to bis(tributyltin) oxide (TBTO) or tributyltin fluoride (TBTF), or for 5 weeks to leachates from tributyltin-containing antibiofouling paints. No larvae survived 8 weeks' exposure to 3 μg/litre TBTO or TBTF. Differential larval survival occurred during exposure to 0·3 gmg/litre of these same compounds. Paint leachates were shown to cause similar toxicity responses at comparable aqueous tributyltin concentrations. An examination of sublethal responses showed slight decreases in growth for larvae exposed to TBTO and to paint leachates, although responses at tributyltin levels below 1 μg/litre were not marked. Whole-animal oxygen consumption rates were not affected by low tributyltin exposure levels. While these studies demonstrate low level toxicity of tributyltins, effects on oxygen consumption and growth do not indicate a mode of action for these compounds.  相似文献   

Bottom Simulating Reflector and Gas Seepage in Okinawa Trough： Evidence of Gas Hydrate in an Active Back-Arc Basin     

栾锡武  Kelin  Wang  Roy  Hyndman  Eleanor  Willoughby 《中国地质大学学报(英文版)》2008,19(2):152-161

To look for gas hydrate, 22 multi-channel and 3 single-channel seismic lines on the East China Sea (ECS) shelf slope and at the bottom of the Okinawa Trough were examined. It was found that there was indeed bottom simulating reflector (BSR) occurrence, but it is very rare. Besides several BSRs, a gas seepage was also found. As shown by the data, both the BSR and gas seepage are all related with local geological structures, such as mud diapir, anticline, and fault-controlled graben-like structure. However, similar structural "anomalies" are quite common in the tectonically very active Okinawa Trough region, but very few of them have developed BSR or gas seepage. The article points out that the main reason is probably the low concentration of organic carbon of the sediment in this area. It was speculated that the rare occurrence of gas hydrates in this region is governed by structure-controlled fluid flow. Numerous faults and fractures form a network of high-permeability channels in the sediment and highly fractured igneous basement to allow fluid circulation and ventilation. Fluid flow in this tectonic environment is driven primarily by thermal buoyancy and takes place on a wide range of spatial scales. The fluid flow may play two roles to facilitate hydrate formation:to help gather enough methane into a small area and to modulate the thermal regime.  相似文献   

Impact of the tsunami and earthquake of 26th December 2004 on the vital coastal ecosystems of the Andaman and Nicobar Islands assessed using RESOURCESAT AWiFS data   总被引：2，自引：0，他引：2  

Anjali Bahuguna  Shailesh Nayak  Dam Roy 《International Journal of Applied Earth Observation and Geoinformation》2008,10(2):229-1

Tsunami waves struck the Indian coast on 26th December 2004 affecting the Andaman and Nicobar group of islands. A quick assessment of the status of the vital coastal ecosystems has been made using pre- and post-tsunami Advance Wide Field Sensor (AWiFS) data of Indian satellite RESOURCESAT with an accuracy of 87–90% and the Kappa ranging from 0.8696 to 0.9053. Among the coastal ecosystems the coral reefs have suffered the maximum with the Nicobar reefs (69% eroded and 29% degraded) bearing the brunt more than the Andaman reefs (54% eroded and 22% degraded). Significant improvement to the condition of the reef damaged due to backwash has been noted. About 41% of the Sentinel reef area has undergone significant improvement. The continuance of the erosion of the southwestern Andaman reefs is due to the impact of recurring earthquakes. The impact on mangroves of both the groups of islands has been due to uprooting as well as inundation of seawater and resulting stagnation. Changes are expected in community structure of mangroves as a result of tsunami.  相似文献   

Heat flow and crustal thermal structure in the Late Archaean Closepet Granite batholith,south India     

Sukanta Roy  Labani Ray  Anurup Bhattacharya  R. Srinivasan 《International Journal of Earth Sciences》2008,97(2):245-256

The Late Archaean Closepet Granite batholith in south India is exposed at different crustal levels grading from greenschist facies in the north through amphibolite and granulite facies in the south along a ∼400 km long segment in the Dharwar craton. Two areas, Pavagada and Magadi, located in the Main Mass of the batholith, best represent the granitoid of the greenschist and amphibolite facies crustal levels respectively. Heat flow estimates of 38 mW m⁻² from Pavagada and 25 mW m⁻² from Magadi have been obtained through measurements in deep (430 and 445 m) and carefully sited boreholes. Measurements made in four boreholes of opportunity in Pavagada area yield a mean heat flow of 39 ± 4 (s.d.) mW m⁻², which is in good agreement with the estimate from deep borehole. The study, therefore, demonstrates a clear-cut heat flow variation concomitant with the crustal levels exposed in the two areas. The mean heat production estimates for the greenschist facies and amphibolite facies layers constituting the Main Mass of the batholith are 2.9 and 1.8 μW m⁻³, respectively. The enhanced heat flow in the Pavagada area is consistent with the occurrence of a radioelement-enriched 2-km-thick greenschist facies layer granitoid overlying the granitoid of the amphibolite facies layer which is twice as thick as represented in the Magadi area. The crustal heat production models indicate similar mantle heat flow estimates in the range 12–14 mW m⁻², consistent with the other parts of the greenstone-granite-gneiss terrain of the Dharwar craton.  相似文献   

The arrangement in mean elements space of the periodic orbits close to that of the Moon     

G. B. Valsecchi  E. Perozzi  A. E. Roy  B. A. Steves 《Celestial Mechanics and Dynamical Astronomy》1993,56(1-2):373-380

In a simplified model of the Earth-Moon-Sun system based on the restricted circular 3-dimensional 3-body problem, it is possible to find numerically a set of 8 periodic orbits whose time evolutions closely resemble that of the Moon's orbit. These orbits have a period of 223 synodic months (i.e. the period of the Saros cycle known for more than two millennia as a means of predicting eclipses), and are characterized by a secular rotation of the argument of perigee . Periodic orbits of longer durations exhibiting this last feature are very abundant in Earth-Moon-Sun dynamical models. Their arrangement in the space of the mean orbital elements- for various values of the lunar mean motion is presented.  相似文献   

Application of soft computing techniques for shallow foundation reliability in geotechnical engineering     

Rahul Ray  Deepak Kumar  Pijush Samui  Lal Bahadur Roy  A.T.C.Goh  Wengang Zhang 《地学前缘(英文版)》2021,12(1):375-383

This research focuses on the application of three soft computing techniques including Minimax Probability Machine Regression(MPMR),Particle Swarm Optimization based Artificial Neural Network(ANN-PSO)and Particle Swarm Optimization based Adaptive Network Fuzzy Inference System(ANFIS-PSO)to study the shallow foundation reliability based on settlement criteria.Soil is a heterogeneous medium and the involvement of its attributes for geotechnical behaviour in soil-foundation system makes the prediction of settlement of shallow a complex engineering problem.This study explores the feasibility of soft computing techniques against the deterministic approach.The settlement of shallow foundation depends on the parametersγ(unit weight),e0(void ratio)and CC(compression index).These soil parameters are taken as input variables while the settlement of shallow foundation as output.To assess the performance of models,different performance indices i.e.RMSE,VAF,R^2,Bias Factor,MAPE,LMI,U(95),RSR,NS,RPD,etc.were used.From the analysis of results,it was found that MPMR model outperformed PSO-ANFIS and PSO-ANN.Therefore,MPMR can be used as a reliable soft computing technique for non-linear problems for settlement of shallow foundations on soils.  相似文献   

Estimation for partially observed Markov processes     

M. E. Thompson  T. N. Kaseke 《Stochastic Hydrology and Hydraulics》1995,9(1):33-47

Many stochastic process models for environmental data sets assume a process of relatively simple structure which is in some sense partially observed. That is, there is an underlying process (X_n, n 0) or (X_t, t 0) for which the parameters are of interest and physically meaningful, and an observable process (Y_n, n 0) or (Y_t, t 0) which depends on the X process but not otherwise on those parameters. Examples are wide ranging: the Y process may be the X process with missing observations; the Y process may be the X process observed with a noise component; the X process might constitute a random environment for the Y process, as with hidden Markov models; the Y process might be a lower dimensional function or reduction of the X process. In principle, maximum likelihood estimation for the X process parameters can be carried out by some form of the EM algorithm applied to the Y process data. In the paper we review some current methods for exact and approximate maximum likelihood estimation. We illustrate some of the issues by considering how to estimate the parameters of a stochastic Nash cascade model for runoff. In the case of k reservoirs, the outputs of these reservoirs form a k dimensional vector Markov process, of which only the kth coordinate process is observed, usually at a discrete sample of time points.  相似文献