65 resultados para in-channel dam
em Publishing Network for Geoscientific
Resumo:
Density and diversity of bottom fauna population as dependent on sediment types and water depth is largely well known in Kiel Bay. This is in contrast to structures and processes of bioturbation, although generally it has a big influence on the benthic boundary layer and its processes, e.g., the metabolism of the bottom fauna, the mechanical properties, the age dating, and the large field of chemical processes. In the densely inhabited sands and muddy sands of the shallower waters with sediment thicknesses of some decimeters only, bioturbation is usually ubiquitous, and most of the structures left are monotonously of "biodeformational" character. At greater water depths, however, where a sedimentary column of several meters of Holocene is developed, the X-ray radiographs of numerous sediment cores show heterogeneous biogenic structures with regional and stratigraphical differentiation. They are described in terms of ichnofabrics and are interpreted on ethological knowledge of the related macrobenthos species. lmportant organisms creating specific traces include the bivalve Arctica (Cyprina) islandica and the polychaete worm Pectinaria koreni. These species are abundant in Kiel Bay and produce by their crawling-plowing mode of locomotion, a characteristic biogenic stratification, the "plow-sole structure". Other typical biogenic structures are tube traces, which are left by a number of different polychaetes occurring either singly, or as U-pairs mainly in mud sediments. Although sea urchins are rare to absent in Kiel Bay, layers of their characteristic traces Scolicia occur as witness of paleohydrographic events in channel sediments of the central bay. Plow-sole traces, polychaete-tube ichnofabric, Scolicia layers and alternations of laminated and bioturbated layers are considered as building blocks of a future "ichnostratigraphy" of Kiel Bay.
Resumo:
This dataset present result from the DFG- funded Arctic-Turbulence-Experiment (ARCTEX-2006) performed by the University of Bayreuth on the island of Svalbard, Norway, during the winter/spring transition 2006. From May 5 to May 19, 2006 turbulent flux and meteorological measurements were performed on the monitoring field near Ny-Ålesund, at 78°55'24'' N, 11°55'15'' E Kongsfjord, Svalbard (Spitsbergen), Norway. The ARCTEX-2006 campaign site was located about 200 m southeast of the settlement on flat snow covered tundra, 11 m to 14 m above sea level. The permanent sites used for this study consisted of the 10 m meteorological tower of the Alfred Wegener Institute for Polar- and Marine Research (AWI), the international standardized radiation measurement site of the Baseline Surface Radiation Network (BSRN), the radiosonde launch site and the AWI tethered balloon launch sites. The temporary sites - set up by the University of Bayreuth - were a 6 m meteorological gradient tower, an eddy-flux measurement complex (EF), and a laser-scintillometer section (SLS). A quality assessment and data correction was applied to detect and eliminate specific measurement errors common at a high arctic landscape. In addition, the quality checked sensible heat flux measurements are compared with bulk aerodynamic formulas that are widely used in atmosphere-ocean/land-ice models for polar regions as described in Ebert and Curry (1993, doi:10.1029/93JC00656) and Launiainen and Cheng (1995). These parameterization approaches easily allow estimation of the turbulent surface fluxes from routine meteorological measurements. The data show: - the role of the intermittency of the turbulent atmospheric fluctuation of momentum and scalars, - the existence of a disturbed vertical temperature profile (sharp inversion layer) close to the surface, - the relevance of possible free convection events for the snow or ice melt in the Arctic spring at Svalbard, and - the relevance of meso-scale atmospheric circulation pattern and air-mass advection for the near-surface turbulent heat exchange in the Arctic spring at Svalbard. Recommendations and improvements regarding the interpretation of eddy-flux and laser-scintillometer data as well as the arrangement of the instrumentation under polar distinct exchange conditions and (extreme) weather situations could be derived.
Resumo:
A rock salt-lamprophyre dyke contact zone (sub-vertical, NE-SW strike) was investigated for its petrographic, mechanic and physical properties by means of anisotropy of magnetic susceptibility (AMS) and rock magnetic properties, coupled with quantitative microstructural analysis and thermal mathematical modelling. The quantitative microstructural analysis of halite texture and solid inclusions revealed good spatial correlation with AMS and halite fabrics. The fabrics of both lamprophyre and rock salt record the magmatic intrusion, "plastic" flow and regional deformation (characterized by a NW-SE trending steep foliation). AMS and microstructural analysis revealed two deformation fabrics in the rock salt: (1) the deformation fabrics in rock salt on the NW side of the dyke are associated with high temperature and high fluid activity attributed to the dyke emplacement; (2) On the opposite side of the dyke, the emplacement-related fabric is reworked by localized tectonic deformation. The paleomagnetic results suggest significant rotation of the whole dyke, probably during the diapir ascent and/or the regional Tertiary to Quaternary deformation.
Resumo:
The marine laboratories in Plymouth have sampled at two principle sites in the Western English Channel for over a century in open-shelf (station E1; 50° 02'N, 4° 22'W) and coastal (station L4; 50° 15'N, 4° 13'W) waters. These stations are seasonally stratified from late-April until September, and the variable biological response is regulated by subtle variations in temperature, light, nutrients and meteorology. Station L4 is characterized by summer nutrient depletion, although intense summer precipitation, increasing riverine input to the system, results in pulses of increased nitrate concentration and surface freshening. The winter nutrient concentrations at E1 are consistent with an open-shelf site. Both stations have a spring and autumn phytoplankton bloom; at station E1, the autumn bloom tends to dominate in terms of chlorophyll concentration. The last two decades have seen a warming of around 0.6°C per decade, and this is superimposed on several periods of warming and cooling over the past century. In general, over the Western English Channel domain, the end of the 20th century was around 0.5°C warmer than the first half of the century. The warming magnitude and trend is consistent with other stations across the north-west European Shelf and occurred during a period of reduced wind stress and increased levels of insolation (+20%); these are both correlated with the larger scale climatic forcing of the North Atlantic Oscillation.
Resumo:
A new technique for the harmonic analysis of current observations is described. It consists in applying a linear band pass filter which separates the various species and removes the contribution of non-tidal effects at intertidal frequencies. The tidal constituents are then evaluated through the method of least squares. In spite of the narrowness of the filter, only three days of data are lost through the filtering procedure and the only requirement on the data is that the time interval between samples be an integer fraction of one day. This technique is illustrated through the analysis of a few French current observations from the English Channel within the framework of INOUT. The characteristics of the main tidal constituents are given.
Resumo:
The marine laboratories in Plymouth have sampled at two principle sites in the Western English Channel for over a century in open-shelf (station E1; 50° 02'N, 4° 22'W) and coastal (station L4; 50° 15'N, 4° 13'W) waters. These stations are seasonally stratified from late-April until September, and the variable biological response is regulated by subtle variations in temperature, light, nutrients and meteorology. Station L4 is characterized by summer nutrient depletion, although intense summer precipitation, increasing riverine input to the system, results in pulses of increased nitrate concentration and surface freshening. The winter nutrient concentrations at E1 are consistent with an open-shelf site. Both stations have a spring and autumn phytoplankton bloom; at station E1, the autumn bloom tends to dominate in terms of chlorophyll concentration. The last two decades have seen a warming of around 0.6°C per decade, and this is superimposed on several periods of warming and cooling over the past century. In general, over the Western English Channel domain, the end of the 20th century was around 0.5°C warmer than the first half of the century. The warming magnitude and trend is consistent with other stations across the north-west European Shelf and occurred during a period of reduced wind stress and increased levels of insolation (+20%); these are both correlated with the larger scale climatic forcing of the North Atlantic Oscillation.