Comparison of bryozoan assemblages from two contrasting Arctic shelf regions     

Piotr Kuklinski  Beate Bader   《Estuarine, Coastal and Shelf Science》2007,73(3-4):835-843

The structure of bryozoan assemblages from two Arctic regions (East Greenland and West Spitsbergen shelf) was compared. Both areas are located at the same latitude and the samples were taken from similar depths; however, the regions differed in water temperature and oceanography. East Greenland, which has lower mean annual water temperatures, was found to be one third richer in taxa (86 species) than West Spitsbergen (59 species). Diversity (Shannon–Wiener index – H′) and abundance were also higher on average in East Greenland (e.g. H′ = 2.49) than West Spitsbergen (e.g. H′ = 2.12). However for species richness, diversity and abundance there were no significant statistical differences between means (ANOVA) from the two regions. In spite of these similarities the investigated assemblages differed to a large extent in both species composition and dominance structure. There were 55 species that occurred only in East Greenland and 28 species that were present only in West Spitsbergen. There was higher proportion of species with an Arctic distribution in East Greenland (46%) than in West Spitsbergen (24%). Observed dissimilarities were concluded to be due to different hydrological conditions between the two regions.  相似文献   

Advances in understanding calcite varve formation: new insights from a dual lake monitoring approach in the southern Baltic lowlands     

Patricia Roeser  Nadine Dräger  Dariusz Brykała  Florian Ott  Sylvia Pinkerneil  Piotr Gierszewski  Christin Lindemann  Birgit Plessen  Brian Brademann  Michał Kaszubski  Michał Fojutowski  Markus J. Schwab  Michał Słowiński  Mirosław Błaszkiewicz  Achim Brauer 《Boreas: An International Journal of Quaternary Research》2021,50(2):419-440

We revise the conceptual model of calcite varves and present, for the first time, a dual lake monitoring study in two alkaline lakes providing new insights into the seasonal sedimentation processes forming these varves. The study lakes, Tiefer See in NE Germany and Czechowskie in N Poland, have distinct morphology and bathymetry, and therefore, they are ideal to decipher local effects on seasonal deposition. The monitoring setup in both lakes is largely identical and includes instrumental observation of (i) meteorological parameters, (ii) chemical profiling of the lake water column including water sampling, and (iii) sediment trapping at both bi-weekly and monthly intervals. We then compare our monitoring data with varve micro-facies in the sediment record. One main finding is that calcite varves form complex laminae triplets rather than simple couplets as commonly thought. Sedimentation of varve sub-layers in both lakes is largely dependent on the lake mixing dynamics and results from the same seasonality, commencing with diatom blooms in spring turning into a pulse of calcite precipitation in summer and terminating with a re-suspension layer in autumn and winter, composed of calcite patches, plant fragments and benthic diatoms. Despite the common seasonal cycle, the share of each of these depositional phases in the total annual sediment yield is different between the lakes. In Lake Tiefer See calcite sedimentation has the highest yields, whereas in Lake Czechowskie, the so far underestimated re-suspension sub-layer dominates the sediment accumulation. Even in undisturbed varved sediments, re-suspended material becomes integrated in the sediment fabric and makes up an important share of calcite varves. Thus, while the biogeochemical lake cycle defines the varves’ autochthonous components and micro-facies, the physical setting plays an important role in determining the varve sub-layers’ proportion.  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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Aerial Orthophoto and Airborne Laser Scanning as Monitoring Tools for Land Cover Dynamics: A Case Study from the Milicz Forest District (Poland)     

Marta Szostak  Piotr Wezyk  Piotr Tompalski 《Pure and Applied Geophysics》2014,171(6):857-866

The paper presents the results from the study concerning the application of airborne laser scanning (ALS) data and derived raster products like the digital surface model (DSM) and the digital terrain model (DTM) for the assessment of the degree of change of the land use based on the forest succession example. Simultaneously, an automated method of ALS data processing was developed based on the normalized (nDSM) and cadastral GIS information. Besides delivering precise information on forest succession, ALS technology is an excellent tool for time-changes spatial analyses. Usage of the ALS data can support the image interpretation process decreasing the subjectivity of the operator. In parallel, a manual vectorization and object classification (object-based image analysis—OBIA) were performed; both based on aerial orthophoto and ALS data. By using integrated ALS point clouds and digital aerial images, one can obtain fast OBIA processing and the determination of areas where the land cover has changed. The Milicz District (central west part of Poland) was chosen as the test site where ALS was to be performed in 2007, together with the digital aerial photos (Vexcel camera; pixel 0.15 m; CIR). The aerial photos were then processed to a CIR orthophoto. The area of study consisted of 68 private parcels (some of them were abandoned; 68.57 ha; scanned cadastral maps from the local survey office; land use information) in the direct neighbourhood of the State Forest, on which a forest succession could often be observed. The operator vectorized forest (trees and shrubs) succession areas on the 2D CIR orthophoto. They were then compared with the results from the OBIA and GIS analysis, based on the normalized digital surface model. The results showed that areas with high vegetation cover were three times larger than the official land cover database (cadastral maps).  相似文献   

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   

Local‐ and regional‐scale biomorphodynamics due to tree uprooting in semi‐natural and managed montane forests of the Sudetes Mountains,Central Europe          下载免费PDF全文

Łukasz Pawlik  Piotr Migoń  Mariusz Szymanowski 《地球表面变化过程与地形》2016,41(9):1250-1265

In this work, direct and indirect geomorphic consequences of wind‐related tree uprooting are examined, using an extensive dataset from the mountain range of the Sudetes, Poland. The role of local conditions in influencing the geomorphic efficacy of tree uprooting is examined, as well as issues of upscaling individual observations from experimental sites. This problem is approached at a range of spatial and observational scales, from monitoring of root plate degradation over time through to examination of wind effects at a slope scale and region‐wide analysis. In our study area the mean root plate volume is between 0.4 and 4.2 m³ for spruce and 2.4 m³ for beech, and their degradation may last tens of years. The density of relict pit‐and‐mound microtopography varies from 2.7 up to 40 pairs per hectare and the maximum coverage of terrain is 4.7%. The volume of treethrow mounds varies from 0.5 to 3.1 m³ and mounds seem to outlive the pits formed in the same episode of disturbance. However, in specific lithological and topographic conditions, pit‐and‐mound topography does not form. The maximum biogenic transport attributable to a single windstorm event is c. 80 m³ ha^?1, while soil turnover times are calculated in the order of 1000–10 000 years. Rock fragment ‘mining’ is an important biogeomorphic process, both in terms of impact on hillslope surfaces and on soil properties. Gravel armours and small‐scale stepped topography may form instead of typical pit–mound associations in specific circumstances. Managed forests appear more prone to wind damage and associated geomorphic consequences. In the Sudetes Mountains, the variable role of tree uprooting in local and regional hillslope denudation is governed by forest stand structure, topography and regolith properties, with the former significantly influenced by human activity. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Interpretation of tracer tests performed in fractured rock of the Lange Bramke basin, Germany   总被引：1，自引：1，他引：0  

Piotr Maloszewski  Andreas Herrmann  Andrzej Zuber 《Hydrogeology Journal》1999,7(2):209-218

 Two multitracer tests performed in one of the major cross-fault zones of the Lange Bramke basin (Harz Mountains, Germany) confirm the dominant role of the fault zone in groundwater flow and solute transport. Tracers having different coefficients of molecular diffusion (deuterium, bromide, uranine, and eosine) yielded breakthrough curves that can only be explained by a model that couples the advective–dispersive transport in the fractures with the molecular diffusion exchange in the matrix. For the scale of the tests (maximum distance of 225 m), an approximation was used in which the influence of adjacent fractures is neglected. That model yielded nearly the same rock and transport parameters for each tracer, which means that the single-fracture approximation is acceptable and that matrix diffusion plays an important role. The hydraulic conductivity of the fault zone obtained from the tracer tests is about 1.5×10^–2 m/s, whereas the regional hydraulic conductivity of the fractured rock mass is about 3×10^–7 m/s, as estimated from the tritium age and the matrix porosity of about 2%. These values show that the hydraulic conductivity along the fault is several orders of magnitude larger than that of the remaining fractured part of the aquifer, which confirms the dominant role of the fault zones as collectors of water and conductors of fast flow. Received, April 1997 Revised, January 1998, August 1998 Accepted, August 1998  相似文献   

Characterization of dissolved organic matter fluorescence in the South Atlantic Bight with use of PARAFAC model: Interannual variability   总被引：13，自引：0，他引：13  

Piotr Kowalczuk  Michael J. Durako  Heather Young  Amanda E. Kahn  William J. Cooper  Michael Gonsior 《Marine Chemistry》2009,113(3-4):182-196

Systematic water sampling for characterization of chromophoric dissolved organic matter (CDOM) in the coastal South Atlantic Bight, was conducted as part of the long term Coastal Ocean Research and Monitoring Program (CORMP). Water samples were collected during a 3.5 year period, from October 2001 until March 2005, in the vicinity of the Cape Fear River (CFR) outlet and in adjacent Onslow Bay (OB). During this study there were two divergent hydrological and meteorological conditions in the CFR drainage area: a severe drought in 2002, followed by the very wet year of 2003. CDOM was characterized optically by the absorption coefficient at 350 nm, the spectral slope coefficient (S), and by Excitation Emission Matrix (EEM) fluorescence. Parallel Factor Analysis (PARAFAC) was used to assess CDOM composition from EEM spectra and six components were identified: three terrestrial humic-like components, one marine humic-like component and two protein-like components. Terrestrial humic-like components contributed most to dissolved organic matter (DOM) fluorescence in the low salinity plume of the CFR. The contribution of terrestrial humic-like components to DOM fluorescence in OB was much smaller than in the CFR plume area. Protein-like components contributed significantly to DOM fluorescence in the coastal ocean of OB and they dominated DOM fluorescence in the Gulf Stream waters. Hydrological conditions during the observation period significantly impacted both concentration and composition of CDOM found in the estuary and coastal ocean. In the CFR plume, there was an order of magnitude difference in CDOM absorption and fluorescence intensity between samples collected during the drought compared to the wet period. During the drought, CDOM in the CFR plume was composed of equal proportions of terrestrial humic-like components (ca. 60% of the total fluorescence intensity) with a significant contribution of proteinaceous substances (ca. 20% of the total fluorescence). During high river flow, CDOM was composed mostly of humic substances (nearly 75% of total fluorescence) with minor contributions by proteinaceous substances. The impact of changes in fresh water discharge patterns on CDOM concentration and composition was also observed in OB, though to a lesser degree.  相似文献   

An isotopic model for the origin of autochthonous organic matter contained in the bottom sediments of a reservoir     

Piotr Koszelnik  Renata Gruca-Rokosz  Lilianna Bartoszek 《国际泥沙研究》2018,33(3):285-293

Geochemical analysis of surface sediment samples collected in 2005 and 2006 was used to evaluate the potential sources of the organic matter present in sediments of southeast Poland's Solina Reservoir.Statistical analysis of sediment variables(carbon to nitrogen ratio, and the carbon 13 and nitrogen 15 isotope ratios) determined for the organic fraction indicated significant spatial variability with respect to sources of organic matter. A binary mixing model was developed from literature sources to predict the relative contributions of allochthonous and autochthonous production to sediment organic matter.Autochthonous production was shown to account for 60-75% of bulk sedimentation in the lacustrine parts of the reservoir, near the dam. In contrast, autochthonous production accounted for only 25% of sedimentation in the riverine zone receiving stream inputs. Statistical analysis identified the δ~(15)N of organic matter as the best predictor of the source of organic matter. Multiple regression analysis indicated that two water-quality variables(nitrate and dissolved silica) were significantly related to the δ~(15)N signature of organic matter. This led to a conclusion that limnetic nitrate and dissolved silica concentrations were regulating organic matter production in the Solina Reservoir.  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