Limnological and sedimentary processes at Sawtooth Lake,Canadian High Arctic,and their influence on varve formation   总被引：1，自引：0，他引：1  

Pierre Francus  Raymond S. Bradley  Ted Lewis  Mark Abbott  Mike Retelle  Joseph S. Stoner 《Journal of Paleolimnology》2008,40(3):963-985

This paper synthesizes data collected to document the modern limnological and sedimentary processes in South Sawtooth Lake located on northern Ellesmere Island, Nunavut, Canada. Field observations show that the finely laminated sediments deposited in the distal basin are formed by the settling of overflows and interflows, and in rare occasions, by non-erosive hyperconcentrated density flows. Thin-sections of these sediments allowed for the classification of the sedimentary fabrics into six facies, each representing different limnological processes. The sediments in this distal basin are considered to be continuous and annually laminated (varved) based on radioisotope analyses, and both limnological and sedimentological evidence.  相似文献   

Variability of Freezing Levels, Melting Season Indicators, and Snow Cover for Selected High-Elevation and Continental Regions in the Last 50 Years     

Henry F. Diaz  Jon K. Eischeid  Chris Duncan  Raymond S. Bradley 《Climatic change》2003,59(1-2):33-52

We have used NCEP/NCAR Reanalysis data and a Northern Hemisphere snow cover data set to analyze changes in freezing level heights and snow cover for the past three to five decades. All the major continental mountain chains exhibit upward shifts in the height of the freezing level surface. The pattern of these changes is generally consistent with changes in snow cover, both over the course of the year and spatially. We examined different free-air temperature parameters (dry bulb temperature, virtual temperature, and 700–500 hPa thickness) using the Reanalysis grid point valueslocated over the different mountain areas as defined in this study. The different trend values were in reasonably good agreement with each other, particularly over the second half of the record.Freezing level changes in the American Cordillera are strongly modulated by the El Niño/Southern Oscillation (ENSO) phenomenon and the freezing level heights (FLH) respond to both interannual and decadal-scale change in tropical Pacific sea surface temperature (SST). The 0.5 °C increase in SST recorded in the tropical Pacific since the 1950s accounts for approximately half of the increase in FLH in tropical and subtropical latitudes of the Cordilleran region during that same time.  相似文献   

Comment on "Ecohydrology--why hydrologists should care"     

Talkington RW 《Ground water》2003,41(5):562-562

  相似文献   

Spatially explicit estimates of erosion-risk indices and variable riparian buffer widths in watersheds   总被引：3，自引：0，他引：3  

Robert?C.?WissmarEmail author  W.?Nicholas?Beer  Raymond?K.?TimmII 《Aquatic Sciences - Research Across Boundaries》2004,66(4):446-455

  相似文献   

187Re,recyclingR-process elements through stars,and the age of the Galaxy     

Raymond J. Talbot Jr. 《Astrophysics and Space Science》1973,20(1):241-249

The enhanced -decay rate of ionized¹⁸⁷Re in stars has been studied within the context of a detailed numerical model of the production ofr-process elements and their recycling through stars during the course of galactic evolution. It is concluded that the enhanced decay rate does not significantly reduce the Re-Os chronometer age for the Galaxy. Consequently, the¹⁸⁷Re -decay half-life and the neutron cross-section ratio (¹⁸⁶Os)/(¹⁸⁷Os) remain as the significant uncertainties in this chronology. Unlike the uncertainties in other chronologies, both are amenable to laboratory measurements.  相似文献   

Observations of the 7 March, 1970 total solar eclipse at wavelengths of 3.2 and 8.3 mm     

John P. Hagen  Paul N. Swanson  Robert W. Haas  Fred L. Wefer  Raymond W. Vogt 《Solar physics》1971,21(2):286-296

The 7 March, 1970 total solar eclipse was observed at wavelengths of 3.2 and 8.3 mm; the object being to use the knife edge of the Moon as it passed across the Sun to improve angular resolution on the Sun. This in turn would provide a radial brightness distribution of the Sun with an angular resolution of a few seconds of arc.Excellent eclipse curves were obtained at 3 mm; however, some external interference marred the 8 mm record near totality.The 8 mm brightness distribution is subject to some uncertainty, but tends to show limb brightening. The 3 mm brightness distribution shows a well defined complex limb brightening within about 1 arc min of the optical limb. The maximum brightening is approximately 30% above the average disc temperature.  相似文献   

Numerical simulation of excavation in elastoplastic soils     

Ronaldo I. Borja  Seung R. Lee  Raymond B. Seed 《国际地质力学数值与分析法杂志》1989,13(3):231-249

  相似文献   

Analysis of leaky sheetpile by Summary Representation     

Gabor M. Karadi  Enrique De Miguel  Raymond J. Krizek 《国际地质力学数值与分析法杂志》1980,4(3):199-213

A numerical technique called Summary Representation was used to solve the problem of seepage through a leaky sheetpile; this particular method was selected owing to its accuracy and computational speed. Seepage parameters were evaluated quantitatively and the influence of the leakiness of sheetpiles in a porous medium underlain by an impervious horizontal stratum was determined. The case of a single sheetpile was first considered, and the effect of the depth of penetration and coefficient of leakiness on the total rate of flow and on the values of the exit gradient was analysed. Next, the flow under an impervious dam was considered to assess the accuracy of the method. Finally, the case of seepage under a dam with leaky sheetpiles at both ends was studied, including the effect of the leaky sheetpiles on the uplift pressure acting along the foundation of the dam. Patterns of seepage through the flow line deformation that is caused by the leakiness of the sheetpiles.  相似文献   

On the dynamics of rotating fluids and planetary atmospheres: A summary of some recent work     

Raymond Hide 《Pure and Applied Geophysics》1983,121(3):365-374

An outline is given of some recent and current research in the Geophysical Fluid Dynamics Laboratory of the UK Meteorological Office, on the dynamics of rotating fluids and planetary atmospheres. Many of these investigations bear on the problem of creating a theoretical framework for atmospheric predictability studies.  相似文献   

Numerical classification applied to certain Jamaican eocene nummulitids     

Raymond M. Wright  Paul Switzer 《Mathematical Geology》1971,3(3):297-311

Eighty-eight specimens of Eocene nummulitids from the Yellow Limestone Formation of northwestern Jamaica are classified according to quantitative measurements of morphologic parameters that are generally considered to be taxonomically useful. The specimens are grouped into homogeneous classes by the computer screening of differently oriented data projections. By this method, the use of similarity coefficients and the question of a priori weighting of characters, for which numerical taxonomy has been heavily criticized, are both avoided. The stability of the classes thus obtained is validated by discriminant analysis. These techniques provide an objective view of phenetic differences among specimens and show how the measured characters produce those differences. Tightness of coiling and total number of whorls, prove to be the most useful features in discriminating between groups but seem to have taxonomic value only at the specific and not at the generic level. This suggests that the generaOperculinoides andNummulites are synonymous.  相似文献