Hydrodynamic Equilibrium for Sediment Transport and Bed Response to Wave Motion

An experimental and theoretical identification of hydrodynamic equilibrium for sediment transport and bed response to wave motion are considered. The comparison between calculations and the results of laboratory experiments indicates the linear relation between sediment transport rate and the thickness zm of bed layer in which sediments are in apparent rectilinear motion. This linear relationship allows to use the first order “upwind” numerical scheme of FDM ensuring an accurate solution of equation for changes in bed morphology. However, it is necessary to carry out a decomposition of the sediment transport into transport in onshore direction during wave crest and offshore direction during wave trough. Further, the shape of bed erosion in response to sediment transport coincides with the trapezoid envelope or with part of it, when some sediments still remain within it. Bed erosion area is equal to the one of a rectangle with thickness znm.     

Revised marine reservoir offset (ΔR) values for molluscs and marine mammals from Arctic North America

Appropriate marine–terrestrial reservoir offset (ΔR) values are essential for accurate calibration of marine radiocarbon dates. However, ΔR values are only valid for the specific calibration curve that their calculation is based on. Here, we present revised ΔR values for the Marine20 calibration curve from Arctic North America, based on previously published ¹⁴C dates on pre-bomb live-collected marine molluscs (n = 124) and cetaceans (beluga whales; tooth dentine; n = 12), and bowhead whale–driftwood age comparisons from the same glacio-isostatically uplifted shorelines (n = 18). Molluscan-based ΔR are: Chukchi/Beaufort sea coasts, 265±116 ¹⁴C years; NW Canadian Arctic Archipelago, 188±91 ¹⁴C years; NE Baffin Island, 81±18 ¹⁴C years; SE Baffin Island, 14±58 ¹⁴C years; Hudson Strait, −73±64 ¹⁴C years; Ungava Bay, 0±86 ¹⁴C years; Foxe Basin, 175±89 ¹⁴C years; Hudson Bay, −21±72 ¹⁴C years; James Bay, 209±114 ¹⁴C years; West Greenland, −93±111 ¹⁴C years. Species-specific marine mammal ΔR terms are 107±59 ¹⁴C years for beluga and 24±58 ¹⁴C years for bowheads. Our revised ΔR values are applicable for as long as the same broad oceanographic conditions (circulation, ventilation) have persisted, i.e. through the Holocene. While molluscan values are applicable to other marine carbonate (e.g. foraminifera), cetacean ΔR are valid only for the species they were calculated for and should not be applied to other marine mammals. Importantly, the ΔR terms calculated here are only valid for Marine20 and should not be used with earlier or later calibration curves.     

Improvement of the geoid in local areas by satellite-to-satellite tracking

Summary The concept of satellite-to-satellite tracking measuring the relative velocity of two orbiting satellites spaced some hundreds kilometers on a close orbit, provides now possibilities for the investigation of the Earth’s gravity field. In the paper only medium and short wave length effects affecting the measured relative velocity have been considered. Collocation is used in such an analysis of local geoid improvement, because this method allows to combine heterogeneous data in a consistent way. Covariance functions relevant for the particular case of a circular equatorial orbit are given. Two kinds of observation equations have been formulated. The choice of observation equation with regard to satellites configuration is discussed. It is found that it is sufficient to have a limited number of satellite-to-satellite observations in a 7^o×7^o area around the estimation point with distances between profiles of about 1^o.5 and between the two satellites forming the pair of 200+350 km; the altitude of satellite-to-satellite observations should be as low as possible. The accuracy of the geoid determination strongly depends on the degree and order of the reference field used. An accuracy of about ±1 m can be achieved with an assumed reference field of (40,40). The influence of measuring errors is discussed and it is shown that only satellite-to-satellite observations with accuracy better then 0.1 mm/sec will give an improvement of the geoid. Finally, some results on the combination of low-low satellite-to-satellite tracking and terrestrial gravity data are given. The proposed method seems to be especially interesting for unsurveyed areas. Furthermore, it has the practical advantage that only a local coverage data is needed.     

Hydrogeochemical background based on spring waters (Lubuskie Lakeland,western Poland)

Hydrogeochemical background determined for an investigated environment, defines characteristic range of its hydrochemical characteristics. This allows to observe the temporal changes of the chemical water properties taking place in the studied environments, such as due to human impact. The paper presents the results of study on the present-day hydrogeochemical background in the Lubuskie Lakeland, the region repeatedly covered by the ice sheets during the Pleistocene and little affected by anthropogenic impact. The hydrogeochemical background was established on a basis of physicochemical analyses of spring waters sampled every 3 months between November 2011 and October 2013 from 20 springs. Present-day hydrogeochemical background was assumed to be represented by values ranging between 16 and 84 percentiles. The ranges of hydrogeochemical background for the studied ions on the Lubuskie Lakeland, were in the lower range of the background considered for useful waters in Poland. The obtained results indicated that the studied spring waters were poorly diversified in terms of composition of main cations and anions, as well as electrical conductivity and total water hardness. However, large variability was observed for Fe_tot, Mn²⁺ and NO₃^?. Moreover, NO₃^? and SO₄^2? were noted in some cases to be in excess of national hydrogeochemical background values.     

A GIS-based WFD oriented typology of shallow micro-tidal soft bottom using wave exposure and turbidity mapping

Our GIS based project aims at producing a classification scheme to develop a typology of the bottom of the Bay of Gdansk in the southern Baltic. The typology was based on the abiotic factors which are used to define water body types by the European Water Framework Directive (WFD). Significance analysis of particular factors has shown that within the discussed area wave exposure seems to play the most important role. All other factors are to a greater or lesser degree correlated with these two. Taking into consideration the shallows and the varied coastline of the investigated area it was decided to make use of the SWAN numerical wave model to determine the influence of wave impact upon the bottom. The model was used to produce raster maps of orbital velocity near the bottom for each wind scenario. With the help of the GIS analysis the maps were turned into layers: the mean velocity and the maximum velocity at the bottom. To produce the layer of yearly amount of solar radiation a GIS model was built which main parameters were the layer of depth and three layers of turbidity for three seasons. The layers of the maximum orbital velocity and of the solar radiation at the bottom were then used in a classificatory procedure consisted in an iterative sequence of the three following steps: cluster formation, dendrogram analysis and classification using the maximum likelihood method. Ecological importance of the classification has been obtained by means of the aggregation of a part of classes based upon the statistics calculated for them within the GIS system with the help of the zonal function out of the following parameters: salinity, depth, mean and maximum orbital velocity at the bottom, temperature differences between warm and cold seasons, solar radiation, and type of sediments. The method proposed here makes it possible to produce high resolution thematic maps of the bottom even with incomplete data cover of the investigated area.     

Deep lithospheric structure beneath the Polish part of the East European Craton as a result of magnetotelluric surveys

Studia Geophysica et Geodaetica - A fundamental tectonic boundary between the Precambrian East European Craton (EEC) and the younger Phanerozoic mountain belts of Europe runs through Poland....