Die Bodenbedeckung des Englischen Kanals und die maximalen Gezeitenstromgeschwindigkeiten

Zusammenfassung Es wurde eine Bodenkarte des Englischen Kanals neu zusammengestellt und darin vier Bodenarten unterschieden: Schlick, Sand, Kies und grober Sand sowie Fels. Ihre Verbreitung wurde mit der Verbreitung der Geschwindigkeitsstufen der maximalen Gezeitenströme dadurch verglichen, da die entsprechenden Areale ausgemessen wurden. Es ergaben sich sowohl zahlenmäig für das Gesamtgebiet wie auch für zahlreiche Einzelfälle enge Beziehungen zwischen den maximalen Gezeitenströmen an der Oberfläche des Englischen Kanals und den Korngröen der Bodenablagerungen.

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The covering of the bottom of the English Channel and the maximum velocities of the tidal currents

Summary A new bottom chart of the English Channel has been designed in which four kinds of bottom covering are distinguished: Mud, sand, shingle and gravel, and rocks. Close correlations were found between the maximum tidal currents at the surface and the grain sizes of the sediments of the English Channel, both numerically for the whole area and for numerous particular cases.

     

Sources,seasonal variability,and trajectories of atmospheric aerosols over central Siberian forest ecosystems

The possibility to obtain reliable data on the chemical and physical characteristics of aerosols and the regularities in the processes of their formation and transportation under the background natural-climatic conditions is a necessary requirement for verification of existing climate models [1, 2].     

Die Wurzeln der alpinen Überschiebungsdecken

Ohne Zusammenfassung     

Das oberengadiner Gebirge,seine Schicht- und Eruptivgesteine sowie der Bau und die Wurzeln seiner Überschiebungsdecken

Ohne Zusammenfassung     

Are there social limits to adaptation to climate change?

While there is a recognised need to adapt to changing climatic conditions, there is an emerging discourse of limits to such adaptation. Limits are traditionally analysed as a set of immutable thresholds in biological, economic or technological parameters. This paper contends that limits to adaptation are endogenous to society and hence contingent on ethics, knowledge, attitudes to risk and culture. We review insights from history, sociology and psychology of risk, economics and political science to develop four propositions concerning limits to adaptation. First, any limits to adaptation depend on the ultimate goals of adaptation underpinned by diverse values. Second, adaptation need not be limited by uncertainty around future foresight of risk. Third, social and individual factors limit adaptation action. Fourth, systematic undervaluation of loss of places and culture disguises real, experienced but subjective limits to adaptation. We conclude that these issues of values and ethics, risk, knowledge and culture construct societal limits to adaptation, but that these limits are mutable.     

A SF6 tracer study of horizontal mixing in Lake Constance

Horizontal mixing processes in the hypolimnion of the western part of Lake Constance are studied by measuring the dispersion of a sulfur hexafluoride (SF₆) tracer plume. Only 1 liter gaseous SF₆ (STP) was released at a central hypolimnic depth of 60 m in August 1990. Over a period of 3 months the horizontal dispersion of the tracer plume was measured by 19 surveys using a new, vertically integrating sampling device. The observed horizontal dispersion is marked by strong storm-induced stirring events. Nevertheless mean turbulent diffusion coefficients for the whole period can be computed. They rise about linear from 0.7 10⁵ cm²/s to 3.0 10⁵ cm²/s with the distance from the western end of the lake. For the hypolimnion of Überlingersee, a sill-separated basin in the western part of Lake Constance, a simple budget model gives an exchange time of 67 ± 6 days with the main basin (Obersee).     

The use of video imagery to analyse groundwater and shoreline dynamics on a dissipative beach

Groundwater seepage is known to influence beach erosion and accretion processes. However, field measurements of the variation of the groundwater seepage line (GWSL) and the vertical elevation difference between the GWSL and the shoreline are limited. We developed a methodology to extract the temporal variability of the shoreline and the wet-dry boundary using video imagery, with the overarching aim to examine elevation differences between the wet-dry boundary and the shoreline position in relation to rainfall and wave characteristics, during a tidal cycle. The wet-dry boundary was detected from 10 min time-averaged images collected at Ngaranui Beach, Raglan, New Zealand. An algorithm discriminated between the dry and wet cells using a threshold related to the maximum of the red, green, and blue intensities in Hue-Saturation-Value. Field measurements showed this corresponded to the location where the water table was within 2 cm of the beachface surface. Time stacks and time series of pixels extracted from cross-shore transects in the video imagery, were used to determine the location of the shoreline by manually digitizing the maximum run-up and minimum run-down location for each swash cycle, and averaging the result. In our test data set of 14 days covering a range of wave and rainfall conditions, we found 6 days when the elevation difference between the wet-dry boundary and the shoreline remained approximately constant during the tidal cycle. For these days, the wet-dry boundary corresponded to the upper limit of the swash zone. On the other 8 days, the wet-dry boundary and the shoreline decoupled with falling tide, leading to elevation differences of up to 2.5 m at low tide. Elevation differences between the GWSL and the shoreline at low tide were particularly large when the cumulative rainfall in the preceding month was greater than 200 mm. This research shows that the wet-dry boundary (such as often used in video shoreline-finding algorithms) is related to groundwater seepage on low-sloped, medium to fine sand beaches such as Ngaranui Beach (mean grain size ∼0.27 mm, beach slope ∼1:70) and may not be a good indicator of the position of the shoreline.     

Inversion-related features along the southeastern margin of the North German Basin (Elbe Fault System)

A seismostratigraphic approach constrained by well data is used for the interpretation of the deformation style along the central Elbe Fault System (EFS) within the sedimentary succession. Structural analysis allows to qualify, to quantify, and to date tectonic events. The stratigraphic interpretation is complicated by the mobilized Upper Permian Zechstein salt and by erosional events. A first-order quantification of the inversion-related uplift is estimated from vertical fault offsets that reach up to 4 km. The main uplift occurred during the Maastrichtian/Paleocene. Amounts of erosion inferred from comparing the strata thickness on top of the Flechtingen High with the surrounding basinal areas range from 3 to 4 km. The data indicate a changing deformation style: Thick-skinned deformation with southwest-dipping thrusts that vertically offset the pre-Permian basement is observed along the Flechtingen High in the central part of the EFS. Thin-skinned deformation occurs in the North German Basin where salt detaches the post-Permian cover from the barely faulted basement. It is concluded that during the Late Cretaceous/Early Tertiary inversion, the EFS responded to regional compression with uplift and formation of an internal high, the Flechtingen High. A stress-sensitive crustal weak zone beneath the EFS could be the reason for the repeated strain localization in the area.