Spatial and seasonal variability of polygonal tundra water balance: Lena River Delta, northern Siberia (Russia)     

Manuel Helbig  Julia Boike  Moritz Langer  Peter Schreiber  Benjamin R. K. Runkle  Lars Kutzbach 《Hydrogeology Journal》2013,21(1):133-147

The summer water balance of a typical Siberian polygonal tundra catchment is investigated in order to identify the spatial and temporal dynamics of its main hydrological processes. The results show that, besides precipitation and evapotranspiration, lateral flow considerably influences the site-specific hydrological conditions. The prominent microtopography of the polygonal tundra strongly controls lateral flow and storage behaviour of the investigated catchment. Intact rims of low-centred polygons build hydrological barriers, which release storage water later in summer than polygons with degraded rims and troughs above degraded ice wedges. The barrier function of rims is strongly controlled by soil thaw, which opens new subsurface flow paths and increases subsurface hydrological connectivity. Therefore, soil thaw dynamics determine the magnitude and timing of subsurface outflow and the redistribution of storage within the catchment. Hydraulic conductivities in the elevated polygonal rims sharply decrease with the transition from organic to mineral layers. This interface causes a rapid shallow subsurface drainage of rainwater towards the depressed polygon centres and troughs. The re-release of storage water from the centres through deeper and less conductive layers helps maintain a high water table in the surface drainage network of troughs throughout the summer.  相似文献   

Review paper: What Kelvin might have written about Elasticity     

Klaus Helbig 《Geophysical Prospecting》2013,61(1):1-20

One hundred and fifty five years ago, Kelvin published the first part of a fundamental analysis of the elastic tensor, in which he proposed a coordinate‐free representation through its eigensystem. His thoughts were apparently far ahead of his time, since it took 125 years before the paper elicited a positive reaction (it is now accessible through several modern reviews). Science not only lost track for 125 years of the original paper but also lost the ideas Kelvin might have proposed in the second part, a publication that was never put to paper, presumably in view of the lack of appreciation of the first part. In an attempt to establish what might have been on Kelvin's mind for a second part, one has to ‘forget’ the progress of mathematical physics in the intervening time and base all arguments strictly on the content of the first part and on the state of science in the second half of the 19^thcentury. The theory of elasticity would certainly have developed faster, had Kelvin's paper peen appreciated by his ‘peers’. But a theory based on Kelvin's ideas would be fruitful even today.  相似文献   

Formation and significance of laurionite in geothermal brine     

Simona Regenspurg  Dejene Legesse Driba  Carolin Zorn 《Environmental Earth Sciences》2016,75(10):865

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Assessing streams in Germany with benthic invertebrates: selection of candidate metrics   总被引：3，自引：0，他引：3  

Daniel Hering  Carolin Meier  Claudia Rawer-Jost  Christian K. Feld  Regina Biss  Armin Zenker  Andrea Sundermann  Susanne Lohse  Jürgen Bhmer 《Limnologica》2004,34(4):398-415

The process of selecting invertebrate-based candidate metrics for the German stream assessment system is described. The aim was to identify metrics indicating degradation types other than organic pollution and acidification (“general degradation”). For 18 out of 24 German stream types a data base of roughly 2,000 benthic invertebrate samples was generated; for each sample 79 metrics were calculated. Data on land use in the catchment were compiled for all sampling sites, together with data on hydromorphology for many sampling sites. Hydromorphological and land use parameters, which describe a clear gradient in the data sets were identified by Non-metric Multidimensional Scaling (NMS). Correlation analyses between land use/hydromorphological parameters and metric results were calculated separately for the individual stream types. Among those metrics best indicating catchment- and hydromorphological degradation in the majority of stream types are: proportion of Ephemeroptera, Plecoptera and Trichoptera; proportion of Plecoptera (mainly suited for mountain streams); number of Plecoptera taxa; proportion of xenosaprobic taxa; proportion of epirhithral preferring taxa. Differences of metric correlations between stream types and between degradation types are discussed, leading to a list of candidate metrics for assessing German streams.  相似文献   

Foreword     

R Cassinis  K Helbig  G.F Panza  Editors 《Journal of Applied Geophysics》1993,29(3-4)

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Optimal estimation of catch by the continuous underway fish egg sampler based on a model of the vertical distribution of American plaice (Hippoglossoides platessoides) eggs     

Pepin  P.; Curtis  K. A.; Snelgrove  P. V. R.; de Young  B.; Helbig  J. A. 《ICES Journal of Marine Science》2007,64(1):18-30

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