Seasonal and spatial changes in the zooplankton community of Kongsfjorden, Svalbard   总被引：1，自引：0，他引：1  

Wojciech Walkusz  Slawek Kwasniewski  Stig Falk-Petersen  Haakon Hop  Vigdis Tverberg  Piotr Wieczorek  & Jan Marcin Weslawski 《Polar research》2009,28(2):254-281

Seasonal changes in the zooplankton composition of the glacially influenced Kongsfjorden, Svalbard (79°N, 12°E), and its adjacent shelf were studied in 2002. Samples were collected in the spring, summer and autumn in stratified hauls (according to hydrographic characteristics), by means of a 0.180-mm Multi Plankton Sampler. A strong front between the open sea and the fjord waters was observed during the spring, preventing water mass exchange, but was not observed later in the season. The considerable seasonal changes in zooplankton abundance were related to the seasonal variation in hydrographical regime. The total zooplankton abundance during the spring (40–2010 individuals m⁻³) was much lower than in the summer and autumn (410–10 560 individuals m⁻³). The main factors shaping the zooplankton community in the fjord include: the presence of a local front, advection, the flow pattern and the decreasing depth of the basin in the inner fjord. Presumably these factors regulate the gross pattern of zooplankton density and distribution, and override the importance of biological processes. This study increased our understanding of seasonal processes in fjords, particularly with regard to the strong seasonal variability in the Arctic.  相似文献   

An assessment study of the wavelet-based index of magnetic storm activity (WISA) and its comparison to the Dst index     

Zhonghua Xu  Lie Zhu  Jan Sojka  Piotr Kokoszka  Agnieszka Jach 《Journal of Atmospheric and Solar》2008,70(11-12):1579-1588

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New fjords,new coasts,new landscapes: The geomorphology of paraglacial coasts formed after recent glacier retreat in Brepollen (Hornsund,southern Svalbard)     

Mateusz C. Strzelecki  Witold Szczuciński  Aleksander Dominiczak  Piotr Zagórski  Justyna Dudek  Jasper Knight 《地球表面变化过程与地形》2020,45(5):1325-1334

Changes in the properties and dynamics of tidewater glacier systems are key indicators of the state of Arctic climate and environment. Calving of tidewater glacier fronts is currently the dominant form of ice mass loss and a major contributor to global sea-level rise. An important yet under-studied aspect of this process is transformation of Arctic landscapes, where new lands and coastal systems are revealed due to the recession of marine-terminating ice masses. The evolution of those freshly exposed paraglacial coastal environments is controlled by nearshore marine, coastal and terrestrial geomorphic processes, which rework glacial-derived sediments to create new coastal paraglacial landforms and landscapes. Here, we present the first study of the paraglacial coasts of Brepollen, one of the youngest bays of Svalbard revealed by ice retreat. We describe and classify coastal systems and the variety of landforms (deltas, cliffs, tidal flats, beaches) developed along the shores of Brepollen during the last 100 years. We further discuss the main modes of sediment supply to the coast in different parts of the new bay, highlighting the fast rate of coastal transformation as a paraglacial response to rapid deglaciation in the Arctic. This study provides an exemplar of likely coastal responses to be anticipated in similar tidewater settings under future climate change. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd  相似文献   

The Outer Part of the Scattered Disc from the Simulation of the Formation of Small-body Reservoirs     

Marián Jakubík  Tomáš Paulech  Luboš Neslušan  Piotr A. Dybczyński  Giuseppe Leto 《Earth, Moon, and Planets》2009,105(2-4):379-383

Considering the model of the initial disc of planetesimals consisting of 10,038 test particles, we simulated the formation of small-body reservoirs in the outer Solar System for the 2-Gyr period. We present the results from the simulation, which concern the part of the scattered disc with objects that have the semi-major axes larger than 50 AU and do not cross the Neptune’s orbit. A suitable border between the scattered disc and the inner Oort cloud, in terms of semi-major axis, appears to be no more than 2,500 AU. The simulated and observed values of perihelion distance and inclination to the Ecliptic typically cover the range between 30 and 40 AU and from 0° to 30°, respectively. No simulated or observed values of the inclination exceed 45°. The distributions of eccentricity and inclination in the simulation are more consistent with their observed counterparts, if the primary observational selection effects are imitated in the simulated distributions.  相似文献   

Stationarity Scores on Training Images for Multipoint Geostatistics   总被引：2，自引：2，他引：0  

Piotr W. Mirowski  Daniel M. Tetzlaff  Roy C. Davies  David S. McCormick  Nneka Williams  Claude Signer 《Mathematical Geosciences》2009,41(4):447-474

This research introduces a novel method to assess the validity of training images used as an input for Multipoint Geostatistics, alternatively called Multiple Point Simulation (MPS). MPS are a family of spatial statistical interpolation algorithms that are used to generate conditional simulations of property fields such as geological facies. They are able to honor absolute “hard” constraints (e.g., borehole data) as well as “soft” constraints (e.g., probability fields derived from seismic data, and rotation and scale). These algorithms require 2D or 3D training images or analogs whose textures represent a spatial arrangement of geological properties that is presumed to be similar to that of a target volume to be modeled. To use the current generation of MPS algorithms, statistically valid training image are required as input. In this context, “statistical validity” includes a requirement of stationarity, so that one can derive from the training image an average template pattern. This research focuses on a practical method to assess stationarity requirements for MPS algorithms, i.e., that statistical density or probability distribution of the quantity shown on the image does not change spatially, and that the image shows repetitive shapes whose orientation and scale are spatially constant. This method employs image-processing techniques based on measures of stationarity of the category distribution, the directional (or orientation) property field and the scale property field of those images. It was successfully tested on a set of two-dimensional images representing geological features and its predictions were compared to actual realizations of MPS algorithms. An extension of the algorithms to 3D images is also proposed. As MPS algorithms are being used increasingly in hydrocarbon reservoir modeling, the methods described should facilitate screening and selection of the input training images.  相似文献   

Surge dynamics of Aavatsmarkbreen,Svalbard, inferred from the geomorphological record          下载免费PDF全文

Ireneusz Sobota  Piotr Weckwerth  Marcin Nowak 《Boreas: An International Journal of Quaternary Research》2016,45(2):360-376

This study investigated the surge dynamics of Aavatsmarkbreen, a glacier in Svalbard and its geomorphological impact based on remote sensing data and field observations. The main objective was to analyse and classify subglacial and supraglacial landforms in the context of glacial deformation and basal sliding over a thin layer of thawed, water‐saturated deposits. The study also focused on the geomorphological evidence of surge‐related sub‐ and supraglacial crevassing and glacier front fracturing. From 2006 to 2013, the average recession of Aavatsmarkbreen was 363 m (52 m a⁻¹). A subsequent surge during 2013–2015 resulted in a substantial advance of the glacier front of over 1 km and an increase in its surface area of more than 2 km². The surface of Aavatsmarkbreen was severely fractured. Significant ice‐flow acceleration was noted whereby the highest surface velocity reached 4.9 m day⁻¹. The ephemeral water‐escape structures and mini‐flutings on the fine‐grained till surface that formed during the surge are indicative of high subglacial pore‐water pressure and enhanced basal sliding. Two genetic types of clast pavements occur in the marginal zone of Aavatsmarkbreen. The results of this study will help to constrain glaciological and geomorphological processes involved in surge phenomena. Understanding the scale and effects of these processes provides insight into the behaviour of fast‐flowing glaciers and ice streams and reveals their relationships with external factors.  相似文献   

Naming conventions in geomorphology: contributions and controversies in the sandstone landscape of Zhangjiajie Geopark,China     

Gary Brierley  He Qing Huang  Anze Chen  Simon Aiken  Mike Crozier  Wolfgang Eder  Andrew Goudie  Yuanxu Ma  Jan‐Hendrik May  Piotr Migon  Gerald Nanson  Deli Qi  Heather Viles  Chris Wood  Robert Wray  Guifang Yang  Xiaoping Yang  Guo‐an Yu 《地球表面变化过程与地形》2011,36(14):1981-1984

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A nonhydrostatic unstructured-mesh soundproof model for simulation of internal gravity waves     

Piotr K. Smolarkiewicz  Joanna Szmelter 《Acta Geophysica》2011,59(6):1109-1134

A semi-implicit edge-based unstructured-mesh model is developed that integrates nonhydrostatic soundproof equations, inclusive of anelastic and pseudo-incompressible systems of partial differential equations. The model builds on nonoscillatory forward-in-time MPDATA approach using finite-volume discretization and unstructured meshes with arbitrarily shaped cells. Implicit treatment of gravity waves benefits both accuracy and stability of the model. The unstructured-mesh solutions are compared to equivalent structured-grid results for intricate, multiscale internal-wave phenomenon of a non-Boussinesq amplification and breaking of deep stratospheric gravity waves. The departures of the anelastic and pseudoincompressible results are quantified in reference to a recent asymptotic theory [Achatz et al. 2010, J. Fluid Mech., 663, 120–147)].  相似文献   

Towards petascale simulation of atmospheric circulations with soundproof equations     

Zbigniew P. Piotrowski  Andrzej A. Wyszogrodzki  Piotr K. Smolarkiewicz 《Acta Geophysica》2011,59(6):1294-1311

This paper highlights progress with the development of a petascale implementation of general-purpose high-resolution (nonoscillatory) hydrodynamical simulation code EULAG [Prusa et al. 2008, Comput. Fluids 37, 1193]. The applications addressed are anelastic atmospheric flows in the range of scales from micro to planetary. The new modeldomain decomposition into a three dimensional processor array has been implemented to increase model performance and scalability. The performance of the new code is demonstrated on the IBM BlueGene/L and Cray XT4/XT5 supercomputers. The results show significant improvement of the model efficacy compared to the original decomposition into a two-dimensional processor array in the horizontal — a standard in meteorological models.  相似文献   

A Map Browser for an Internet-based GIS Data Repository     

Piotr Jankowski  Milosz Stasik  & Maria A. Jankowska 《Transactions in GIS》2001,5(1):5-18

This article presents the design of a map browser for an Internet-based GIS data repository. A map browser called GeoLibrary was developed and implemented as a component of the Idaho Geospatial Data Center (IGDC), a digital library of public-domain GIS data for the state of Idaho. The design and implementation of the map browser are introduced in the larger context of a geolibrary model. The article also discusses alternative solutions that can be considered for implementing a map browser.  相似文献