Baltic cod recruitment - the impact of climate variability on key processes   总被引：3，自引：0，他引：3  

Koster  Friedrich W.; Mollmann  Christian; Hinrichsen  Hans-Harald; Wieland  Kai; Tomkiewicz  Jonna; Kraus  Gerd; Voss  Rudiger; Makarchouk  Andrei; MacKenzie  Brian R.; St. John  Michael A.; Schnack  Dietrich; Rohlf  Norbert; Linkowski  Tomasz; Beyer  Jan E. 《ICES Journal of Marine Science》2005,62(7):1408-1425

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Prediction of UT1–UTC,LOD and AAM χ<Subscript>3</Subscript> by combination of least-squares and multivariate stochastic methods     

Tomasz Niedzielski  Wiesław Kosek 《Journal of Geodesy》2008,82(2):83-92

This article presents the application of a multivariate prediction technique for predicting universal time (UT1–UTC), length of day (LOD) and the axial component of atmospheric angular momentum (AAM χ ₃). The multivariate predictions of LOD and UT1–UTC are generated by means of the combination of (1) least-squares (LS) extrapolation of models for annual, semiannual, 18.6-year, 9.3-year oscillations and for the linear trend, and (2) multivariate autoregressive (MAR) stochastic prediction of LS residuals (LS + MAR). The MAR technique enables the use of the AAM χ ₃ time-series as the explanatory variable for the computation of LOD or UT1–UTC predictions. In order to evaluate the performance of this approach, two other prediction schemes are also applied: (1) LS extrapolation, (2) combination of LS extrapolation and univariate autoregressive (AR) prediction of LS residuals (LS + AR). The multivariate predictions of AAM χ ₃ data, however, are computed as a combination of the extrapolation of the LS model for annual and semiannual oscillations and the LS + MAR. The AAM χ ₃ predictions are also compared with LS extrapolation and LS + AR prediction. It is shown that the predictions of LOD and UT1–UTC based on LS + MAR taking into account the axial component of AAM are more accurate than the predictions of LOD and UT1–UTC based on LS extrapolation or on LS + AR. In particular, the UT1–UTC predictions based on LS + MAR during El Niño/La Niña events exhibit considerably smaller prediction errors than those calculated by means of LS or LS + AR. The AAM χ ₃ time-series is predicted using LS + MAR with higher accuracy than applying LS extrapolation itself in the case of medium-term predictions (up to 100 days in the future). However, the predictions of AAM χ ₃ reveal the best accuracy for LS + AR.  相似文献   

Gamma-ray bursts from high velocity neutron stars     

Tomasz Bulik  Donald Q. Lamb 《Astrophysics and Space Science》1995,231(1-2):373-376

We investigate the viability of the Galactic corona model of -ray bursts by calculating the spatial distribution of neutron stars born with high velocities in the Galactic disk, and comparing the resulting brightness and angular distribution with the BATSE data. We find that the Galactic corona model can reproduce the BATSE peak flux and angular distribution data for neutron star kick velocities 800 km s^–1, source turn-on ages 10 Myrs, and sampling depths 100 kpc d _max 400 kpc.  相似文献   

Sedimentary facies and climate control on formation of vivianite and siderite microconcretions in sediments of Lake Baikal, Siberia     

Tomasz Sapota  Ala Aldahan  Ihsan S. Al-Aasm 《Journal of Paleolimnology》2006,36(3):245-257

Authigenic vivianite and siderite microconcretions were found, respectively, in hemipelagic and deltaic facies of 600-m-long BDP-98 sediment section from Lake Baikal. Textural investigations of these microconcretions show that they are typically <1 mm in size, irregular in shape and composed of aggregated crystallites. Dissimilar orientation of vivianite and siderite crystallites suggests formation at different depths in the sediment; up to tens of centimeters for vivianite and tens of meters for siderite. Chemical analyses of both the vivianite and the siderite indicate cation composition characterized by minor amounts of Mn, Ca and Mn apart from the dominating Fe. Rather limited and distinctive carbon isotopic composition of the siderite, with δ ¹³C_VPDB values between about +13 and +16‰, implies formation of the mineral in the methanogenic zone of diagenesis. Isotopic composition of oxygen in the siderite (δ ¹⁸O_VPDB values between about −10 and -11‰ ) is consistent with crystallization temperature at about 10–30°C and water δ ¹⁸O_SMOW values between about −10 and -16‰ . The distribution of the authigenic minerals in the section suggests changes in both sedimentary facies and climate, where vivianite formation was controlled by hemipelagic depositional conditions during the Pliocene and Quaternary, whereas siderite reflects impact of deltaic conditions during the Miocene.  相似文献   

A reconstruction of the palaeohydrological conditions of a flood‐plain: a multi‐proxy study from the Grabia River valley mire,central Poland          下载免费PDF全文

Dominik Pawłowski  Grzegorz Kowalewski  Krystyna Milecka  Mateusz Płóciennik  Michał Woszczyk  Tomasz Zieliński  Daniel Okupny  Wojciech Włodarski  Jacek Forysiak 《Boreas: An International Journal of Quaternary Research》2015,44(3):543-562

This study investigated the Grabia River valley mire in central Poland to reconstruct its palaeoenvironmental conditions from the Younger Dryas to the present. We analysed sedimentological, biological and geochemical data from the palaeo‐oxbow lake and valley mire to identify the principal hydrological trends, especially episodes of high water level. During the Lateglacial and Holocene, the Grabia River had a meandering channel, and its hydraulic parameters and the channel dimensions changed in response to climatic oscillations and vegetation development. We identified phases of high flood intensity and high groundwater level that correlate with regional and supraregional climatic events. The frequency and timing of palaeohydroclimatic oscillations show strong similarities to records from other sites in Poland and the rest of Europe. We show that various analytical methods, namely, pollen, plant macrofossils, Cladocera, Chironomidae, sedimentological, geochemical and radiocarbon data, can be effective tools for reconstructing past hydroclimatic changes in palaeo‐oxbow lakes and investigating the effects of past climate changes on river environments. The high sensitivity of the biota, especially Cladocera, to changes in water level permits the reconstruction of palaeoecological changes, especially flood episodes that occurred in the river valley. In particular, the increase in the proportion of sediment‐associated Cladocera and pelagic taxa was closely correlated with floods. Through comparisons with the palaeobiological data, geochemical data allowed the identification of humid phases within the fen associated with a rising groundwater table, direct fluvial activity (floods) and alluvial deposition. We also discuss the limitations of palaeohydrological reconstructions based on these proxies, especially on fossil aquatic invertebrates.  相似文献   

Map-Based Web Tools Supporting Climate Change Adaptation     

Tina-Simone Neset  Tomasz Opach  Peter Lion  Anna Lilja  Jimmy Johansson 《The Professional geographer》2016,68(1):103-114

This article discusses the state of the art in geovisualization supporting climate change adaptation. We reviewed twenty selected map-based Web tools, classified by their content and functionality, and assessed them by visual representations, interactive functions, information type, target audience, and how vulnerability and adaptation to climate change are addressed. Our study concludes that the tools (1) can be classified as data viewers with basic functionality and data explorers offering more sophisticated interactive functions; (2) mostly feature moderate or high richness of data content; and (3) predominantly target expert users.  相似文献   

The geochemical study of groundwaters from Cenozoic aquifers in the Gwda catchment (Western Pomerania,Poland)     

Tomasz Kotowski  Marek Kachnic 《Environmental Earth Sciences》2016,75(3):192

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A thermo-plastic constitutive law for brittle-plastic behavior of rocks at high temperatures     

Tomasz Hueckel  Alberto Peano  Rita Pellegrini 《Pure and Applied Geophysics》1994,143(1-3):483-510

Mechanical properties of rocks change under the influence of, temperature. Stress at the onset of yielding, ultimate strength, dilatancy, strain hardening and softening, and the confining pressure at brittle-ductile transition are all reduced by the increasing temperature. This study presents a framework of constitutive modeling of thermo-brittle-plastic behavior of rocks which encompasses these changes. The constitutive law is based on a thermo-plasticity theory first proposed for metals byPrager (1958). Two phenomenological mechanisms have been identified as central for the modeling: temperature dependence of the yield locus (thermal softening), and temperature dependence of the strain-hardening function (thermally enhanced ductility). Material parameters for two rocks, Carrara marble and Westerly granite, were determined on the basis of additional hypotheses. These parameters are used in numerical simulations of triaxial tests at different temperatures. The obtained stress-strain curves compare well to the experimental results. The changes with temperature in the stress at the onset of yielding are more accurately reproduced that the evolution of hardening or softening. Suggestions for possible improvements and future research directions are indicated.  相似文献   

A data-based regional scale autoregressive rainfall-runoff model: a study from the Odra River     

Tomasz Niedzielski 《Stochastic Environmental Research and Risk Assessment (SERRA)》2007,21(6):649-664

This paper aims to compare the performances of multivariate autoregressive (MAR) techniques and univariate autoregressive (AR) methods applied to regional scale rainfall-runoff modelling. We focus on the case study from the upper and middle reaches of the Odra River with its main tributaries in SW Poland. The rivers drain both the mountains (the Sudetes) and the lowland (Nizina Śląska). The region is exposed to extreme hydrologic and meteorological events, especially rain-induced and snow-melt floods. For the analysis, four hydrologic and meteorological variables are chosen, i.e., discharge (17 locations), precipitation (7 locations), thickness of snow cover (7 locations) and groundwater level (1 location). The time period is November 1971–December 1981 and the temporal resolution of the time series is of 1 day. Both MAR and AR models of the same orders are fitted to various subsets of the data and subsequently forecasts of discharge are derived. In order to evaluate the predictions the stepwise procedure is applied to make the validation independent of the specific sample path of the stochastic process. It is shown that the model forecasts peak discharges even 2–4 days in advance in the case of both rain-induced and snow-melt peak flows. Furthermore, the accuracy of discharge predictions increases if one analyses the combined data on discharge, precipitation, snow cover, and groundwater level instead of the pure discharge multivariate time series. MAR-based discharge forecasts based on multivariate data on discharges are more accurate than AR-based univariate predictions for a year with a flood, however, this relation is reverse in the case of the free-of-flooding year. In contrast, independently of the occurrence of floods within a year, MAR-based discharge forecasts based on discharges, precipitation, snow cover, and groundwater level are more precise than AR-based predictions.  相似文献   

Creep of saturated materials as a chemically enhanced rate‐dependent damage process     

Liang Bo Hu  Tomasz Hueckel 《国际地质力学数值与分析法杂志》2007,31(14):1537-1565

Material behaviour that exhibits characteristics of creep induced by a spontaneous mineral dissolution enhanced by material damage is studied. It is believed that the characteristic rates of the chemical processes involved determine the time‐rate dependence of the resulting strain. A basic model of a combined chemo‐plastic softening and chemically enhanced deviatoric strain hardening for saturated geomaterials is presented. Chemical softening is postulated to occur as a consequence of the net mass removal resulting from dissolution and precipitation of specific minerals occurring at the damage‐generated inter‐phase interfaces. Closed and open systems are discussed. In the former case, deformation at constant stress results entirely from a local compensation mechanism between the chemical softening and strain hardening. The classical three stages of creep are interpreted in terms of mechanisms of dissolution and precipitation, as well as the variation in the reaction surface areas involved in the mass exchange. In an open system, the above local mechanism is enhanced by the removal of mass via diffusion of species affecting the mass balance. Such a system is addressed via a boundary value problem as shown in an example. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献