Trophic modeling of the Northern Humboldt Current Ecosystem, Part II: Elucidating ecosystem dynamics from 1995 to 2004 with a focus on the impact of ENSO   总被引：1，自引：1，他引：0  

Marc H. Taylor  Jorge Tam  Vernica Blaskovic  Pepe Espinoza  R. Michael Balln  Claudia Wosnitza-Mendo  Juan Argüelles  Erich Díaz  Sara Purca  Noemi Ochoa  Patricia Ayn  Elisa Goya  Dimitri Gutirrez  Luis Quipuzcoa  Matthias Wolff 《Progress in Oceanography》2008,79(2-4):366

The Northern Humboldt Current Ecosystem is one of the most productive in the world in terms of fish production. Its location near to the equator permits strong upwelling under relatively low winds, thus creating optimal conditions for the development of plankton communities. These communities ultimately support abundant populations of grazing fish such as the Peruvian anchoveta, Engraulis ringens. The ecosystem is also subject to strong inter-annual environmental variability associated with the El Niño Southern Oscillation (ENSO), which has major effects on nutrient structure, primary production, and higher trophic levels. Here our objective is to model the contributions of several external drivers (i.e. reconstructed phytoplankton changes, fish immigration, and fishing rate) and internal control mechanisms (i.e. predator-prey) to ecosystem dynamics over an ENSO cycle. Steady-state models and time-series data from the Instituto del Mar del Perú (IMARPE) from 1995 to 2004 provide the base data for simulations conducted with the program Ecopath with Ecosim. In simulations all three external drivers contribute to ecosystem dynamics. Changes in phytoplankton quantity and composition (i.e. contribution of diatoms and dino- and silicoflagellates), as affected by upwelling intensity, were important in dynamics of the El Niño of 1997–98 and the subsequent 3 years. The expansion and immigration of mesopelagic fish populations during El Niño was important for dynamics in following years. Fishing rate changes were the most important of the three external drivers tested, helping to explain observed dynamics throughout the modeled period, and particularly during the post-El Niño period. Internal control settings show a mix of predator–prey control settings; however a “wasp-waist” control of the ecosystem by small pelagic fish is not supported.  相似文献   

Scleractinian cold-water corals in the Gulf of Cádiz—First clues about their spatial and temporal distribution     

Claudia Wienberg  Dierk Hebbeln  Hiske G. Fink  Furu Mienis  Boris Dorschel  Agostina Vertino  Matthias Lpez Correa  Andr Freiwald 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(10):1873-1893

This paper presents the first compilation of information on the spatial distribution of scleractinian cold-water corals in the Gulf of Cádiz based on literature research and own observations (video footage, sediment samples). Scleractinian cold-water corals are widely distributed along the Spanish and Moroccan margins in the Gulf of Cádiz, where they are mainly associated with mud volcanoes, diapiric ridges, steep fault escarpments, and coral mounds. Dendrophyllia cornigera, Dendrophyllia alternata, Eguchipsammia cornucopia, Madrepora oculata and Lophelia pertusa are the most abundant reef-forming species. Today, they are almost solely present as isolated patches of fossil coral and coral rubble. The absence of living scleractinian corals is likely related to a reduced food supply caused by low productivity and diminished tidal effects. In contrast, during the past 48 kyr scleractinian corals were abundant in the Gulf of Cádiz, although their occurrence demonstrates no relationship with main climatic or oceanographic changes. Nevertheless, there exists a conspicuous relationship when the main species are considered separately. Dendrophylliids are associated with periods of relatively stable and warm conditions. The occurrence of L. pertusa mainly clusters within the last glacial when bottom current strength in the Gulf of Cádiz was enhanced and long-term stable conditions existed in terms of temperature. Madrepora oculata shows a higher tolerance to abrupt environmental changes.  相似文献   

The mid-depth circulation of the northwestern tropical Atlantic observed by floats     

Matthias Lankhorst  David Fratantoni  Michel Ollitrault  Philip Richardson  Uwe Send  Walter Zenk 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(10):1615-1632

A comprehensive analysis of velocity data from subsurface floats in the northwestern tropical Atlantic at two depth layers is presented: one representing the Antarctic Intermediate Water (AAIW, pressure range 600–1050 dbar), the other the upper North Atlantic Deep Water (uNADW, pressure range 1200–2050 dbar). New data from three independent research programs are combined with previously available data to achieve blanket coverage in space for the AAIW layer, while coverage in the uNADW remains more intermittent. Results from the AAIW mainly confirm previous studies on the mean flow, namely the equatorial zonal and the boundary currents, but clarify details on pathways, mostly by virtue of the spatial data coverage that sets float observations apart from e.g. shipborne or mooring observations. Mean transports in each of five zonal equatorial current bands is found to be between 2.7 and 4.5 Sv. Pathways carrying AAIW northward beyond the North Brazil Undercurrent are clearly visible in the mean velocity field, in particular a northward transport of 3.7 Sv across 16°N between the Antilles islands and the Mid-Atlantic Ridge. New maps of Lagrangian eddy kinetic energy and integral time scales are presented to quantify mesoscale activity. For the uNADW, mean flow and mesoscale properties are discussed as data availability allows. Trajectories in the uNADW east of the Lesser Antilles reveal interactions between the Deep Western Boundary Current (DWBC) and the basin interior, which can explain recent hydrographic observations of changes in composition of DWBC water along its southward flow.  相似文献   

长江口及邻近海域表层沉积物中重金属元素含量分布及其影响因素   总被引：8，自引：2，他引：6  

董爱国  翟世奎  ZABEL Matthias  于增慧 《海洋学报》2009,31(6):54-68

根据2003和2006年长江口及邻近海域表层沉积物样品的粒度组成和元素铬、铜、镍、铅、锌、铝、钙和锶的含量,分析了重金属元素含量的分布特征,探讨了含量的变化趋势及其对人类活动的响应。自2003年三峡工程一期蓄水完成到2006年6月,长江输沙量逐年减少,长江口海域沉积物中黏土的百分含量明显增加,但是沉积物分布的总体格局并没有发生明显的变化。重金属元素大多在泥质区沉积物中富集,高值区沿岸线呈带状分布,在最大浑浊带和口外羽状锋处达到峰值。在长江大量物质输入的背景下,研究区沉积物中重金属元素含量相对其他类似河口较低。河流的陆源颗粒输入、水动力条件、细颗粒物质的吸附以及絮凝作用是控制沉积物中重金属元素含量分布的主要因素,氧化还原条件也对重金属元素含量变化有一定的影响。人类活动(重大工程的建设和人为污染)对长江口外泥质区中重金属元素含量有重要影响,尤其对铅和锌的含量及其分布的影响显著。自2003年三峡工程一期蓄水以来,长江口海域表层沉积物中重金属元素沉积机制未有明显的变化,但是重金属元素含量有逐渐降低的趋势。  相似文献   

The upper limit of glaciation in the Himalayas     

Matthias Kuhle 《GeoJournal》1986,13(4):331-346

On the slopes of Himalayan Mountains there is a reduction and culmination of glaciation at 7000–7200 m asl. The presumed cause for this is that the surface temperatures on these slopes are too low for glaciation. This working hypothesis was verified with temperature measurements using collected infra-red radiation. The regression analysis of the measurements taken in the Mt. Everest region during sunny weather conditions of the post-monsoon season resulted in a 0°C line at 7000–7200 m asl. The coincidence of the 0°C line with the upper limit of glaciation is causally definable with the copula between the function of temperature and snow metamorphism: since it is too cold above 7000–7200 m asl, metamorphism into perennial or galcial ice through settling or sintering is absent or simply too slow. High relief and drifting hinder here the processes of ice-formation through pressure compaction of the dry-snow accumulation caused by molecular diffusion and recrystallization. Above 7200 m only continuous leeward accumulations of shifting snow on wall sections with moderate inclination lead to the formation of seracs. However, glaciation generally ceases at this level. This additionally confirms another study. It has been proven that Himalayan glaciers with catchment areas over 7000 m do not extend further downward than those glaciers whose catchment areas just reach this altitude. A break in balance at 7100 m asl is thereby confirmed, and the upper glacial limit is proven. Above the glacial region a rocky zo ne adjoins with pergelic conditions even in the surface layer. This zone is covered by snow during monsoon season only. Here, the weathering processes take place in an arid environment without thawing and purely by means of temperature variations below 0°C. They could correspond to those occurring on a larger scale on the planets of our solar system.A lowering of the upper glacial limit by at least 660 or 1200 m respectively, analogous to the Pleistocene snow-line depression reconstructed in S Tibet and the Central Himalayas, is assumed during the Ice Age.The author gratefully acknowledges the translation of this paper rendered by Dr. J. A. Hellen, Newcastle-upon-Tyne.  相似文献   

The petrography of Southern Tibet     

Annerose Heydemann Dr.  Matthias Kuhle Dr. 《GeoJournal》1988,17(4):615-624

Summary Mineralogical investigations of rock samples from the Transhimalaya and Tibetan Himalaya allow the conclusion that during the last glaciations in this area there was long distance glacial transport. The samples from the Mt. Everest group, the highest region of the continental crust, provide an account of the petrological data collected from this area. They depict a juxtaposition of sedimentary series and granitic intrusive bodies and also extreme tectonic action deep into their cystalline structure.  相似文献   

Constraints on dark energy models from galaxy clusters with multiple arcs     

Massimo Meneghetti  Bhuvnesh Jain  Matthias Bartelmann  Klaus Dolag 《Monthly notices of the Royal Astronomical Society》2005,362(4):1301-1310

  相似文献   

Influence of low ozone episodes on erythemal UV-B radiation in Austria     

Schwarz  Matthias  Baumgartner  Dietmar J.  Pietsch  Helga  Blumthaler  Mario  Weihs  Philipp  Rieder  Harald E. 《Theoretical and Applied Climatology》2018,133(1-2):319-329

This study investigates the influence of low ozone episodes on UV-B radiation in Austria during the period 1999 to 2015. To this aim observations of total column ozone (TCO) in the Greater Alpine Region (Arosa, Switzerland; Hohenpeissenberg, Germany; Hradec Kralove, Czech Republic; Sonnblick, Austria), and erythemal UV-B radiation, available from 12 sites of the Austrian UV-B monitoring network, are analyzed. As previous definitions for low ozone episodes are not particularly suited to investigate effects on UV radiation, a novel threshold approach—considering anomalies—is developed to provide a joint framework for the analysis of extremes. TCO and UV extremes are negatively correlated, although modulating effects of sunshine duration impact the robustness of the statistical relationship. Therefore, information on relative sunshine duration (SD_rel), available at (or nearby) UV-B monitoring sites, is included as explanatory variable in the analysis. The joint analysis of anomalies of both UV index (UVI) and total ozone (∆UVI, ∆TCO) and SD_rel across sites shows that more than 65% of observations with strongly negative ozone anomalies (∆TCO < −1) led to positive UVI anomalies. Considering only days with strongly positive UVI anomaly (∆UVI > 1), we find (across all sites) that about 90% correspond to negative ∆TCO. The remaining 10% of days occurred during fair weather conditions (SD_rel ≥ 80%) explaining the appearance of ∆UVI > 1 despite positive TCO anomalies. Further, we introduce an anomaly amplification factor (AAF), which quantifies the expected change of the ∆UVI for a given change in ∆TCO.

  相似文献   

The microscale cooling effects of water sensitive urban design and irrigation in a suburban environment     

Ashley?M.?BroadbentEmail authorView author&#;s OrcID profile  Andrew?M.?Coutts  Nigel?J.?Tapper  Matthias?Demuzere  Jason?Beringer 《Theoretical and Applied Climatology》2018,131(1-2):1-17

There is still considerable uncertainty about precipitation at high elevation in mountain terrain due to the relatively few in situ measurements available and to the particular variability of the parameter. In this study, several spatialization techniques were tested, some for climatological time scale and others for daily fields, for precipitation over the western Alps for the period of 1990–2012. The study domain and period were chosen for the quality of available in situ observations and density of the network. First, a weather-type classification was established with a technique based on canonical correlation analysis combining large- and regional-scale data. The spatialization techniques applied for the climatological time scale were adapted from the Aurelhy method which uses elevation and principal components of the topography as predictors. The spatialization techniques applied to daily fields were based on kriging of daily rain gauges and used the climatological fields as predictors. This study aims to validate the advantage of using the climatology of the weather type of the day as predictor for daily fields over a monthly climatology. The climatology of the weather type of the day seems to demonstrate some small improvement.Finally, annual means over the period of 1990–2012 were produced using several methods, including some from accumulation of daily fields and others from the spatialization of in situ station means. Precipitation at high elevations and vertical climatological gradients were particularly scrutinized. Annual means based on sums of daily fields seem to have better performances.This paper only presents results for precipitation but temperature was also analysed.  相似文献   

The Othris Ophiolite, Greece: A snapshot of subduction initiation at a mid-ocean ridge     

Matthias G. Barth  Paul R.D. Mason  Gareth R. Davies  Martyn R. Drury 《Lithos》2008,100(1-4):234-254

The mantle section of the Tethyan-type Othris Ophiolite, Greece, records tectono-magmatic processes characteristic of both mid-ocean ridges and supra-subduction zones. The Othris Ophiolite is a remnant of the Jurassic Neotethys Ocean, which existed between Eurasia and Gondwanaland. Othris peridotites range from fertile plagioclase lherzolites to depleted harzburgites. Abundances of Al₂O₃ and CaO show well-defined inverse linear correlations with MgO, suggesting that the Othris peridotites formed as residua from variable degrees of partial melting.

Peridotites from the Fournos Kaïtsa and western Katáchloron sub-massifs are similar to abyssal peridotites and can be explained by a multistage model with some melting in the garnet stability field followed by moderate degrees of anhydrous near-fractional melting in the spinel stability field. In contrast, the peridotites from the Metalleio, Eretria, and eastern Katáchloron sub-massifs, and the Vourinos ophiolite are highly depleted and have extremely low concentrations of Al₂O₃ and heavy rare earth elements. These peridotites have enriched light REE contents compared to the middle REE. These residua are best modelled by hydrous melting due to a flux of slab-derived fluid to the mantle wedge during melting.

The occurrence of both styles of melting regimes within close spatial and temporal association in the same ophiolite is explained by intra-oceanic thrusting and forced subduction initiation at (or near) a mid-ocean ridge. Thus, the Othris Ophiolite, and probably Tethyan-type ophiolites in general, represent a transient phase of plate tectonic reorganisation rather than quasi-steady state plate tectonics.  相似文献