Oceanographic influences on seabirds and cetaceans of the eastern tropical Pacific: A review     

Lisa T. Ballance  Robert L. Pitman  Paul C. Fiedler 《Progress in Oceanography》2006,69(2-4):360

This paper is part of a comprehensive review of the oceanography of the eastern tropical Pacific, the oceanic region centered on the eastern Pacific warm pool, but also including the equatorial cold tongue and equatorial current system, and summarizes what is known about oceanographic influences on seabirds and cetaceans there. The eastern tropical Pacific supports on the order of 50 species of seabirds and 30 species of cetaceans as regular residents; these include four endemic species, the world’s largest populations for several others, three endemic sub-species, and a multi-species community that is relatively unique to this ecosystem. Three of the meso-scale physical features of the region are particularly significant to seabirds and cetaceans: the Costa Rica Dome for blue whales and short-beaked common dolphins, the Equatorial Front for planktivorous seabirds, and the countercurrent thermocline ridge for flocking seabirds that associate with mixed-species schools of spotted and spinner dolphins and yellowfin tuna. A few qualitative studies of meso- to macro-scale distribution patterns have indicated that some seabirds and cetaceans have species-specific preferences for surface currents. More common are associations with distinct water masses; these relationships have been quantified for a number of species using several different analytical methods. The mechanisms underlying tropical species–habitat relationships are not well understood, in contrast to a number of higher-latitude systems. This may be due to the fact that physical variables have been used as proxies for prey abundance and distribution in species–habitat research in the eastern tropical Pacific.Though seasonal and interannual patterns tend to be complex, species–habitat relationships appear to remain relatively stable over time, and distribution patterns co-vary with patterns of preferred habitat for a number of species. The interactions between seasonal and interannual variation in oceanographic conditions with seasonal patterns in the biology of seabirds and cetaceans may account for some of the complexity in species–habitat relationship patterns.Little work has been done to investigate effects of El Niño-Southern Oscillation cycles on cetaceans, and results of the few studies focusing on oceanic seabirds are complex and not easy to interpret. Although much has been made of the detrimental effects of El Niño events on apex predators, more research is needed to understand the magnitude, and even direction, of these effects on seabirds and cetaceans in space and time.  相似文献   

ENSO variability and the eastern tropical Pacific: A review   总被引：3，自引：0，他引：3  

Chunzai Wang  Paul C. Fiedler 《Progress in Oceanography》2006,69(2-4):239

El Niño-Southern Oscillation (ENSO) encompasses variability in both the eastern and western tropical Pacific. During the warm phase of ENSO, the eastern tropical Pacific is characterized by equatorial positive sea surface temperature (SST) and negative sea level pressure (SLP) anomalies, while the western tropical Pacific is marked by off-equatorial negative SST and positive SLP anomalies. Corresponding to this distribution are equatorial westerly wind anomalies in the central Pacific and equatorial easterly wind anomalies in the far western Pacific. Occurrence of ENSO has been explained as either a self-sustained, naturally oscillatory mode of the coupled ocean–atmosphere system or a stable mode triggered by stochastic forcing. Whatever the case, ENSO involves the positive ocean–atmosphere feedback hypothesized by Bjerknes. After an El Niño reaches its mature phase, negative feedbacks are required to terminate growth of the mature El Niño anomalies in the central and eastern Pacific. Four requisite negative feedbacks have been proposed: reflected Kelvin waves at the ocean western boundary, a discharge process due to Sverdrup transport, western Pacific wind-forced Kelvin waves, and anomalous zonal advections. These negative feedbacks may work together for terminating El Niño, with their relative importance being time-dependent.ENSO variability is most pronounced along the equator and the coast of Ecuador and Peru. However, the eastern tropical Pacific also includes a warm pool north of the equator where important variability occurs. Seasonally, ocean advection seems to play an important role for SST variations of the eastern Pacific warm pool. Interannual variability in the eastern Pacific warm pool may be largely due to a direct oceanic connection with the ENSO variability at the equator. Variations in temperature, stratification, insolation, and productivity associated with ENSO have implications for phytoplankton productivity and for fish, birds, and other organisms in the region. Long-term changes in ENSO variability may be occurring and are briefly discussed. This paper is part of a comprehensive review of the oceanography of the eastern tropical Pacific.  相似文献   

A review of eastern tropical Pacific oceanography: Summary     

M.F. Lavín  P.C. Fiedler  J.A. Amador  L.T. Ballance  J. Frber-Lorda  A.M. Mestas-Nuez 《Progress in Oceanography》2006,69(2-4):391

The collection of articles in this volume reviewing eastern tropical Pacific oceanography is briefly summarized, and updated references are given. The region is an unusual biological environment as a consequence of physical characteristics and patterns of forcing – including a strong and shallow thermocline, the ITCZ and coastal wind jets, equatorial upwelling, the Costa Rica Dome, eastern boundary and equatorial current systems, low iron input, inadequate ventilation of subthermocline waters, and dominance of ENSO-scale temporal variability. Remaining unanswered questions are presented.  相似文献   

Side-scan and acoustic subbottom characterization of the sea floor near the Dry Tortugas, Florida     

Thomas F. Wever  Hannelore M. Fiedler  Gunther Fechner  Friedrich Abegg  Ingo H. Stender 《Geo-Marine Letters》1997,17(4):246-252

 Between 2 and 6 February, 1995, a 25 km² area at the Dry Tortugas (Florida Keys) was surveyed with a 100 kHz side-scan sonar system and 3.5-kHz subbottom profiler. The side-scan system revealed a pattern of alternating high and low backscatter. The subbottom profiler showed areas with no acoustic penetration between sediment troughs. The combination of both methods allowed delineation of the boundaries in high-backscatter regions, and sediment samples allowed correlations between high backscatter and coarser-grained sediments.  相似文献   

Palaeoclimatic studies in South Shetland Islands,Antarctica, based on numerous stratigraphic variables in lake sediments     

Svante Björck  Hannelore Håkansson  Siv Olsson  Lena Barnekow  Jan Janssens 《Journal of Paleolimnology》1993,8(3):233-272

The hitherto longest found lake sediment sequence on Byers Peninsula, Livingston Island, South Shetland Islands, was analysed with respect to lithology, chronology, diatoms, Pediastrum, pollen and spores, mosses, mineralogy, and sediment chemistry. During the ca. 5000 year long development the sediments were influenced by frequent tephra fall-outs. This volcanic impact played a major role in the lake's history during two periods, 4700–4600 and 2800–2500 BP, but was of importance during the lake's entire history with considerable influence on many of the palaeoenvironmentally significant indicators. The large and complex data set was analysed and zonated with different types of multivariate analysis. This resulted in a subdivision of the sequence into 8 time periods and 21 variables. Redundancy analysis (RDA) of this data set, both without and with the tephra periods, and with 4–6 of the variables as explanatory environmental variables, reveal that climatic/environmental signals are detectable. The palaeoclimatic picture that emerged out of the tephra noise suggests that the first 100 years were characterized by mild, humid conditions. This was followed by a less mild and humid climate until ca. 4000 BP when a gradual warming seems to have started, coupled with increased humidity. These mild and humid conditions seem to have reached an optimum slightly after 3000 BP. At ca. 2500 BP a distinct climatic deterioration occurred with colder and drier conditions and long seasons with ice cover. This arid, cold phase probably reached its optimum conditions at ca. 1500 BP, when slightly warmer conditions might have prevailed for a while. Except for the modern sample with rather mild climate, the last 1400 years seem to have been fairly arid and cold, and the effects of the frequent volcanic activity during this period is only vaguely seen in the records.  相似文献   

A Simplified Analytical Procedure for the Determination of Organically Bound Halogens in Salt‐containing Water Samples     

Helko Borsdorf  Petra Fiedler  Dorit Wilke  Holger Weiß 《洁净——土壤、空气、水》2003,31(1):19-24

A method was developed for the determination of organic halogens in water samples with the aim of minimizing matrix effects and simplifying the sample preparation technique commonly used. The method is based on the adsorption of organic halogens in modified hydrophilic divinylbenzene polymer columns and their elution with methanol. The adsorbent used enables rapid adsorption and desorption due to comparatively high operating flow rates and minimized solvent amounts. Furthermore, no additional reconcentration steps are needed. The methanol extract obtained is combusted with a standard EOX (extractable organic halogen) analyzer and the concentration of organically bound halogens is determined by microcoulometric analysis. The matrix effects are considerably reduced compared to the standard procedure (EN 1485) commonly used. A detection limit of 13 μg/L was established.  相似文献   

Regional effects of large-scale extreme wind events over orographically structured terrain     

N. Kalthoff  I. Bischoff-Gauß  F. Fiedler 《Theoretical and Applied Climatology》2003,74(1-2):53-67

Summary ?Above orographically structured terrain considerable differences of the regional wind field may be identified during large-scale extreme wind events. So far, these regional differences could not be resolved by climate models. To determine the relationships between large-scale atmospheric conditions, the influence of orography, and the regional wind field, data measured in the upper Rhine valley within the framework of the REKLIP Regional Climate Project were analyzed and calculations were made using the KAMM mesoscale model. In the area of the upper Rhine valley, ratios of the wind velocity in the Rhine valley at 10 m above ground level, ν_val, and the large-scale flow velocity, ν_lar, are between ν_val/ν_lar ≈ 0.1 and ν_val/ν_lar ≈ 1. The ν_val/ν_lar ratio exhibits a strong dependence on thermal stratification, δ, and decreases from ν_val/ν_lar ≈ 1 at δ = 0 K m⁻¹ to ν_val/ν_lar ≈ 0.2 at δ = 0.0075 K m⁻¹. In areas, where the lateral mountainous border of the Rhine valley is interrupted, the ν_val/ν_lar ratio increases again with increasing stability or decreasing Froude number. This is obviously due to flow around the Black Forest under stable stratification. It is demonstrated by model calculations that a complex wind field develops in the Rhine valley at small Froude numbers (Fr < 1) irrespective of the direction of large-scale flow. The ν_val/ν_lar ratio is characterized by small values in the direct lee side (ν_val/ν_lar ≈ 0.2) and high values on the windward side of the lateral mountainous border of the Rhine valley (ν_val/ν_lar ≈ 0.8). Received October 22, 2001; revised June 18, 2002; accepted June 23, 2002  相似文献   

The Holocene paleolimnology of Lake Sämbosjön,southwestern Sweden     

Gunnar Digerfeldt  Hannelore Håkansson 《Journal of Paleolimnology》1993,8(3):189-210

The Holocence paleolimnology of Lake Sämbosjön is described using geochemical and diatom analyses. The objective of this study is the reconstruction of major changes in trophic state and productivity, and to interpret the major causative processes. The accumulation of organic matter indicates a relatively high productivity in early Holocene, and the diatom analysis indicates a relatively high trophic state and pH. A succeeding decrease in productivity and trophic state and lowering in pH is recorded from about 8000 BP. If lake development had been primarily edaphically conditioned, viz. determined by nutrient supply from catchment soils, such a progressive oligotrophication would represent the common development of temperate lakes. Between about 6000 BP and 4000 BP Lake Sämbosjön was characterized by relatively stable productivity and pH. From about 4000 BP the analyses reveal an increase again in trophic state, productivity, and in pH. This eutrophication, which continued throughout the late Holocene, was caused by an exceptionally strong human influence on the catchment of Lake Sämbosjön. The increased supply of nutrients from cleared and deforested catchment soils changed the trophic state and provided the basis for increased lake productivity.  相似文献   

On the accuracy of location of local shocks on the territory of Czechoslovakia and adjacent areas     

Libuše Ruprechtová  Klára Mrázová  Jaroslav Fiedler  Reviewer A. Zátopek 《Studia Geophysica et Geodaetica》1984,28(3):286-293

Summary The calculation procedures for determining epicentre parameters of weak near shocks with foci in Poland are discussed and tested for explosions with known epicentres.

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Die seismische Aktivität in Venezuela im Zusammenhang mit den wichtigsten tektonischen Bruchzonen     

Dr. G. Fiedler 《International Journal of Earth Sciences》1970,59(3):1203-1215

Zusammenfassung Einem kurzen Überblick über die geologischen und tektonischen Zusammenhänge in den wichtigsten venezolanischen Erdbebengebieten folgt eine standardisierte Betrachtung der Einzelbeben, deren Magnitude gleich oder größer als 5,5 war. Die aus makroseismischer Intensität und/oder Magnitude (Richter) berechnete, ausgelöste Erdbebenenergie, summiert über 440 Jahre bekannter Erdbebengeschichte Venezuelas, wurde graphisch dargestellt. Die Neigung der so erhaltenen Energietreppen ist ein Maß für die Seismizität, i.e. der Vertikalabstand der Parallelen zwischen Maxima und Minima ist ein Maß für die größtmögliche Magnitude eines Erdbebens aus der entsprechenden Herdregion, und aus den zeitlichen Abständen der Energietreppen lassen sich Schlüsse ziehen über Erdbebenhäufigkeit bzw. Erdbebenerwartung. Schließlich wurde für alle Beben das der ausgelösten seismischen Energie unter gegebenen Voraussetzungen entsprechendeErdbebenvolumen berechnet, an die Erdoberfläche projiziert und als Epizentralgebiete in einer Isoseistenkarte dargestellt, in welchen Wellenbewegungen und Krustendeformationen zu erwarten sind. Besonders Brucherscheinungen sollten dann sichtbar sein, wenn eine der Oberflächen des Volumens mit der Erdoberfläche zusammenfällt. Mittels einer für alle größeren venezolanischen Erdbeben aus makroseismischen Beobachtungen berechneten Intensitäts-Abklingkonstanten c wurde schließlich eine Isoseistenkarte für Venezuela entworfen, in welcher mögliche Überlagerungen aus allen seismischen Zonen des Landes berücksichtigt wurden. Diese Karte kann als Grundlage für die Planung erdbebensicherer Bauten und für geotektonische Zwecke benutzt werden.

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A brief synopsis of the geological and tectonical context of the most important Venezuelan earthquake regions is followed by a standardized treatment of the single earthquakes with magnitudes greater then 5,5. From intensity and/or magnitude (Richter), the earthquake energy released was calculated, added up for the 440 years of known earthquake history of Venezuela, and presented in graphs. The slope of such cumulative energy histogram is a measure of the seismicity, i.e. the distance between the two parallel lines, which connect the maxima and the minima, gives an idea of the possible maximum magnitude in each region; from the time intervals of the steps one may draw conclusions concerning earthquake frequency and earthquake expectation. Finally the earthquake volume for each single quake, which under given conditions corresponds to the energy released, was calculated, its surfaces were projected on the earth's surface and mapped as epicentral regions of an isoseismal map, in which wave motion and crustal deformations may be expected. Special fracture features should be visible where one of the surfaces of the volume intersects the earth's surface. By means of an intensity decay constant c, which was determined from macroseismic observations for each greater earthquake, the isoseismal map for Venezuela was drawn, in which possible intensity superpositions of all seismic regions were taken into consideration. This map may be used as a base for earthquake engineering and geotectonical purposes.

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Résumé Un bref aperçu sur les rapports géologiques et tectoniques dans les régions de tremblements de terre les plus importantes au Vénézuéla est suivi d'une étude standardisée des tremblements individuels, dont la magnitude était égale ou supérieure à 5,5. L'énergie sismique dégagée, calculée à partir de l'intensité macro-sismique et/ou de la magnitude (Richter), accumulée pendant 440 ans d'histoire connue des tremblements au Vénézuéla, est représentée à l'aide d'esquisses graphiques. L'inclinaison des «escaliers d'énergie» qui en résultent est la mesure de la sismicité, c'est-à-dire la distance verticale des lignes parallèles entre maxima et minima est la mesure de la magnitude la plus grande possible d'un tremblement de la région sismique en question, et on peut déduire des intervalles de temps entre les escaliers d'énergie des conclusions sur la fréquence et la prévision des tremblements. Enfin, pour tous les tremblements le volume de tremblement correspondant sous des conditions données à l'énergie sismique dégagée est calculé, projeté sur la surface de la terre et représenté sur une carte isoséiste comme régions épicentrales où l'on peut prévoir un mouvement d'ondes et des déformations de l'écorce. En particulier, des phénomènes de fraction doivent être visibles quand l'une des surfaces du volume coincide avec la surface de la terre. Finalement, à l'aide d'une constante d'intensité diminuée «c», calculée pour tous les tremblements de terre majeurs du Vénézuéla par des observations macrosismiques une carte isoséiste est dessinée pour le Vénézuéla, dans laquelle il est tenu compte des superpositions possibles de toutes les zones sismiques du pays. Cette carte peut servir de base pour le projet de bâtiments résistant aux séismes et à des buts géotectoniques.

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