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  • American Chemical Society  (1)
  • American Meteorological Society  (1)
  • Blackwell Publishing Ltd  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 110 (1992), S. 0 
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: In a hydrothermally active ocean basin, vigorous hydrothermal circulation in highly permeable basement rocks maintains a nearly constant temperature at the base of the overlying accumulating sediment section. To investigate the thermal effects of sedimentation in such geological settings, we have developed a simple one-dimensional finite element model and applied it to cases in the northeast Pacific. The model accounts for differential motion of fluids and sediment grains during compaction, and can be used with any porosity-depth function. Results demonstrate clearly that the constant basal temperature of an accumulating sediment section, maintained by convective heat transfer in the basement, causes the section to remain thermally near steady state for even very high rates of accumulation, particularly when compared to conditions estimated for a section where heat is transported in the basement by conduction. A 10-kyr period of thermal recovery due to the highly diminished sediment supply during the post-Pleistocene further reduces the thermal effects of sedimentation by a significant amount. Only in rare cases where rates of accumulation exceed 10 mm yr−1 and sediment thicknesses exceed 1 km are the sea-floor heat flow and temperatures at depth diminished significantly. An example is found in Middle Valley of the Juan de Fuca Ridge, in a part of which over 2 km of sediment has accumulated in the past 200 kyr. Even in this extreme case, the heat flow is estimated to be lower than that of the steady state by about only 15 per cent. While rates of accumulation are also high in other parts of Middle Valley and in many other hydrothermally active areas, such as Guayamas Basin, Escanaba Trough and the eastern flank of the Juan de Fuca Ridge, these rates and the accumulated sediment thicknesses are found to be insufficient to cause appreciable thermal anomalies.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2017-10-01
    Description: Karst landforms cover 7%–12% of the Earth’s continental area and provide water resources for 25% of the global population. Climate, particularly frequent climate extremes, may greatly affect the annual runoff, especially in climate-sensitive regions such as a karst area of southwest China. Knowledge of the linkage between climate and runoff is urgently needed for smart water resources management. This study therefore selected five catchments that have different carbonized rock coverage (from 11% to 64%) to detect the dominant climatic variables driving changes in annual runoff for the period of 1957–2011 in southwest China. Because climatic variables are highly codependent, a partial least squares regression (PLSR) was used to elucidate the linkages between runoff and 17 climatic variables. Results indicated that the dominant climatic factors driving annual runoff are annual total precipitation, rainy days, heavy precipitation amount, heavy precipitation days, rainstorm amount, and rainstorm days. These six factors are generally used to represent extreme climatic events, and hence it may demonstrate that annual runoff is highly linked to precipitation extremes in this region. The PLSR approach presented in this study is beneficial and novel, as it enables the elimination of codependency among the variables and facilitates a more unbiased view of the contribution of the changes in climatic variables to the changes in runoff. As a practical and simple tool, the PLSR approach is thus recommended for application to a variety of other catchments.
    Print ISSN: 1525-755X
    Electronic ISSN: 1525-7541
    Topics: Geography , Geosciences , Physics
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  • 3
    Publication Date: 2019-04-10
    Print ISSN: 0003-2700
    Electronic ISSN: 1520-6882
    Topics: Chemistry and Pharmacology
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