On the current profile in the German Bight: A two-month BroadBand ADCP time series of high vertical resolution

Summary A bottom mounted BroadBand ADCP was deployed for about two months in the German Bight (54° 15.3′, N, 7° 35.5′ E) at 40 m depth. The ADCP recorded current data and echo intensity between 3 and 38m depth with a vertical resolution of 1 m. The data, which provide continuous vertical current profiles, are investigated with regard to the vertical variations of residual and tidal currents and kinetic energies. To investigate the temporal variability of the current profiles, the time series are subdivided into 8-day intervals. Furthermore, the data are compared with historical data. According to the ADCP profiles, the water column can be subdivided into three layers: A primarily wind-driven near-surface layer (∼10m), a middepth layer with great directional variability, and a near-bottom layer of about 10 m thickness with a strictly logarithmic current profile.

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über das Stromprofil in der Deutschen Bucht: Eine zweimonatige BroadBand ADCP Zeitserie mit hoher vertikaler Aufl?sung

Zusammenfassung Ein am Boden stehender BroadBand ADCP wurde für zwei Monate in der Deutschen Bucht (54° 15.3′ N, 7° 35.5′ E) in 40 m Wassertiefe eingesetzt. Er registrierte Str?mungsdaten und Echointensit?t zwischen 3 und 38 m Wassertiefe mit einer vertikalen Aufl?sung von 1 m. Dieser Datensatz, der kontinuierliche vertikale Stromprofile liefert, wird hinsichtlich der vertikalen Variation von Rest- und Gezeitenstr?men und kinetischer Energie analysiert. Zur Untersuchung der zeitlichen Variabilit?t der Stromprofile wird die Gesamtzeitserie in 8-Tage-Intervalle unterteilt. Ferner werden die Ergebnisse mit historischen Messungen verglichen. Aus den ADCP-Profilen ergibt sich eine prinzipielle Dreiteilung der Wassers?ule: Eine vorwiegend windgetriebene oberfl?chennahe Schicht (∼10m), eine mittlere Schicht mit hoher Richtungsvariabilit?t und eine etwa 10 m m?chtige Bodenschicht mit streng logarithmischem Stromprofil.

     

Dynamic soil–structure interaction of coupled shear walls by boundary element method

For a class of civil engineering structures, that can be accurately represented by ‘coupled shear walls’ (CSWs), a discrete model for the analysis of the dynamic interaction with the underlying soil is proposed. The CSWs, with one or more rows of openings, rest on a rigid foundation embedded in the elastic or viscoelastic half-space. A hierarchical finite element model based on an equivalent continuum approach is adopted for the structure. A frequency-domain boundary element method is used to represent the half-space. Finally, the set of equations governing the response of the coupled soil-structure system to harmonic lateral loads acting on the structure is also given. The frequency deviation effect with respect to the fixed-base structure and the effects of radiation and material damping in the soil are presented for different characteristics of the structure and different soil properties.     

Pressure anomalies in the Indian Ocean area, 1796–1960

Summary Barometric anomalies for stations near the Indian Ocean since 1841 are tabulated and combined for years and half-years. Early records for India yield a further series back to 1796. Regional anomalies for the west Indian Ocean correlate inversely with Nile Flood data, and those for the east Indian Ocean inversely with Java tree-rings. Combined values (including Australia), if reversed, correlate well with such rainfall indicators and at the same time provide good indicators of the half-yearly anomalies of the Southern Oscillation and the yearly anomalies of the Pressure Parameter. The Pressure Parameter is an index linked also with tropical temperature changes and with climatic fluctuations in various parts of the world.

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Zusammenfassung Luftdruckwerte für Orte im Gebiete des Indischen Ozeans seit 1841 wurden zusammengestellt in Tabellen jährlicher und halbjährlicher Anomalien. Frühe Aufzeichnungen in Indien sind erhältlich seit 1796. Regionale Anomalien des Luftdruckes im westlichen Indischen Ozean sind umgekehrt korreliert mit der Nilflut, solche im östlichen Indischen Ozean mit den Jahresringbreiten von Bäumen auf Java. Kombinierte Luftdruckanomalien (Australien eingeschlossen) sind umgekehrt korreliert mit solcherart Indikatoren des Niederschlags und ergeben zur gleichen Zeit gute Anweisungen für die halbjährlichen Anomalien der sogenannten Südlichen Schwankung und der jährlichen Anomalien eines gewissen Luftdruckparameters. Der Luftdruckparameter ist verbunden mit tropischen Temperaturänderungen und klimatischen Schwankungen in verschiedenen Weltteilen.

     

Assessment of the feasibility of utilizing Landsat for detection and monitoring of landfills in a statewide GIS

Use of satellite data could be beneficial and cost effective in detecting and monitoring landfills in a state-wide geographic information system (GIS). To assure the feasibility of this approach, multitemporal Landsat data were used to detect several selected active and inactive landfills in central and southwest Missouri. The landfills were visually delineated from aerial photography of approximately the same two dates. A classification procedure based on homogeneity of the digital numbers was performed on each landfill scene for each time period using four spectral bands: two visible, one near-infrared, and one mid-infrared. The mid-infrared band proved more useful in delineating landfills, especially when spectral change was compared to the near-infrared band. The active landfills were spectrally different from surrounding land cover as were the two landfills which closed after the collection of the first Landsat scene. These landfills showed considerable areal change between the two selected time periods as verified by the aerial photographs. The inactive landfills were more difficult to discern from surrounding land cover types because they were grass covered and spectrally similar to pasture. Consequently, areal change could not be assigned to these older landfills because the reclamation process was practically complete.     

Tidal triggering of reservoir-associated earthquakes

If the effect of a reservoir is to bring a fault zone gradually to failure and trigger an earthquake, then it is reasonable that rapidly fluctuating tidal stresses may influence the time of the induced earthquakes. An examination of earthquakes from eight reservoirs shows that earthquakes at six sites occur at preferred times in the semidiurnal tidal cycle. Tidal-stress orientations and the phase within the semidiurnal tidal cycle were calculated for only the largest earthquakes occurring at each site. This insures the elimination of aftershocks and selects earthquakes which are independent of each other. Sites of a significant earthquake/tide correlation with less than a 3% chance of occurring randomly include Hebgen Lake, Mont., U.S.A.; Kariba, Rhodesia; Kerr Dam, Mont., U.S.A.; Kremasta, Greece; Lake Mead, Nev., U.S.A.; and Monteynard, France. Each data set includes from about ten to twenty earthquakes. In most of the above cases earthquake triggering seems to occur when tidal stress enhances slip, i.e., when tidal stresses are oriented to enhance the tectonic stress.     

Drainage area and the variation of channel geometry downstream

Recent geomorphological studies tend to deal with small basins. The understanding of small basin dynamics provides important information for the understanding of large basin dynamics assuming that the extrapolation of small basin data to larger basins is valid. This work tests the validity of this extrapolation of data with reference to channel geometry. An analysis of the variation of channel width downstream reveals that the value b =0.5 (W = aQ^b) is a ‘good’ average. However, the use of a one-line model consisting of a simple power function incurs a loss of a considerable amount of relevant information concerning the channel form and hence the channel processes. It has been shown that the –b– value for small basins and very big basins is lower than the one for the intermediate basins.     

The relevance of Old World archeology to the first entry of man into the New World

Archeological evidence from the USSR suggests that cultural adaptations to the most rigorous (most continental) environments of northern Eurasia were not achieved until 35–40,000 BP. This presumably sets an absolute basement date for the entry of man into Alaska through the region of Beringia. The absence of evidence for pre-14,000 yr old man in the 48 adjacent United States comparable in any sense to the evidence that has been developed for man prior to 14,000 y.a. in the Old World suggests that movement south out of Alaska only occurred after 14,000 BP.     

Measurement of electromagnetic effects generated by swell

Many studies have been conducted on swell, some of which have been particularly concerned with its associated magnetic field. One of us (M.K.) has reconsidered some of the theoretical studies which have been made, with attention given to the practical case of an ocean of finite depth.In the marine magnetotelluric program on the continental shelf, the Geophysical Research Center at Garchy has obtained records of the variation of the magnetic-field components in an ocean twenty meters deep.After having presented the hypothesis of the theoretical calculation, we give some computer-drawn chart (P.L.) and some power-density spectra of records obtained in the Mediterranean Sea. Some recent results on the electric field permits us to conclude that these first results are due to the magnetic field associated with swell and we discuss some implications of these results.     

Taking the uncertainty in climate-change vulnerability assessment seriously

Climate-change vulnerability assessment has become a frequently employed tool, with the purpose of informing policy-makers attempting to adapt to global change conditions. However, we suggest that there are three reasons to suspect that vulnerability assessment often promises more certainty, and more useful results, than it can deliver. First, the complexity of the system it purports to describe is greater than that described by other types of assessment. Second, it is difficult, if not impossible, to obtain data to test proposed interactions between different vulnerability drivers. Third, the time scale of analysis is too long to be able to make robust projections about future adaptive capacity. We analyze the results from a stakeholder workshop in a European vulnerability assessment, and find evidence to support these arguments. To cite this article: A. Patt et al., C. R. Geoscience 337 (2005).