High variability and exceptionally low thermal conductivities in nearshore sediments: a case study from the Eckernförde Bay

IF 1.6 4区 地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS
Regina Usbeck, M. Dillon, N. Kaul, A. Lohrberg, F. Nehring, A. C. Ploetz
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Abstract

Heat flow measurements are a standard technique in Geophysics both onshore and offshore. Recently, such measurements became increasingly important in shallow waters. The increasing amount of offshore power installations makes it necessary to have a good knowledge about the subsurface heat flow and the thermal properties of the sediments to optimize the construction of the necessary powerlines. While the thermal properties are well studied for deep ocean sediments, only few published data exist for nearshore sediments. In this study, we investigate the sediment temperatures and thermal conductivities of nearshore sediments in the German part of the Baltic Sea. The shallow sediment temperatures reflect the interplay of the response to the seasonal cycle in connection with the sediments’ thermal conductivity. We find thermal conductivity values ranging from 0.67 to 3.34 W/(m*K) for the sediments down to ~ 4.2 m below seafloor. This variability exceeds that of conservative estimates widely used for coastal sediments and is also much higher than the variability found in the deep oceans. Sandy sediments show thermal conductivities larger than 1 W/(m*K) whereas organic-rich muds have lower values (< 1 W/(m*K)). Furthermore, the thermal conductivities seem to decrease with increasing free gas content in the sediment. The latter needs to be confirmed by further investigations.

Abstract Image

近岸沉积物的高变异性和异常低的热导率:Eckernförde湾的案例研究
热流测量是陆上和海上地球物理学的一项标准技术。最近,这种测量在浅水区变得越来越重要。随着海上电力设施数量的增加,有必要对地下热流和沉积物的热特性有很好的了解,以优化必要的电力线的建设。虽然对深海沉积物的热性质研究得很好,但对近岸沉积物的研究却很少。在这项研究中,我们研究了波罗的海德国部分近岸沉积物的沉积温度和热导率。浅层沉积物温度反映了对季节循环响应的相互作用,与沉积物的热导率有关。我们发现海底以下~ 4.2 m的沉积物的热导率值为0.67 ~ 3.34 W/(m*K)。这种变异性超过了广泛用于沿海沉积物的保守估计,也远远高于在深海中发现的变异性。砂质沉积物的热导率大于1 W/(m*K),而富有机质泥的热导率小于1 W/(m*K)。此外,热导率似乎随着沉积物中游离气体含量的增加而降低。后者需要进一步的调查来证实。
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来源期刊
Marine Geophysical Research
Marine Geophysical Research 地学-地球化学与地球物理
CiteScore
2.80
自引率
14.30%
发文量
41
审稿时长
>12 weeks
期刊介绍: Well-established international journal presenting marine geophysical experiments on the geology of continental margins, deep ocean basins and the global mid-ocean ridge system. The journal publishes the state-of-the-art in marine geophysical research including innovative geophysical data analysis, new deep sea floor imaging techniques and tools for measuring rock and sediment properties. Marine Geophysical Research reaches a large and growing community of readers worldwide. Rooted on early international interests in researching the global mid-ocean ridge system, its focus has expanded to include studies of continental margin tectonics, sediment deposition processes and resulting geohazards as well as their structure and stratigraphic record. The editors of MGR predict a rising rate of advances and development in this sphere in coming years, reflecting the diversity and complexity of marine geological processes.
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