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Modeling the estuarine circulation and fine sediment transport associated with subglacial buoyant jets in glacial fjords

机译：模拟与冰川峡湾下冰川浮力射流有关的河口环流和细沙输送

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摘要

It has been suggested that high latitude systems are one of the regions where the consequences of global warming are becoming more evident. From an oceanographic point of view, glacial fjords are particularly sensitive to climate change because of the seasonal dynamics of sea-ice formation and melting and the important amount of sediment delivered by tidewater glaciers. Our understanding of glacial fjords dynamics in the context of global warming, however, has been the subject of study only during the last two decades. Glacial fjords are estuaries whose complexity arise from a combination of submarine freshwater discharges, as buoyant jets, a highly non-hydrostatic process. Although buoyant jets and sediment transport associated with these processes have received attention through experimental, numerical and field studies, an integrated study of these processes and the estuarine circulation in glacial ford has been missing. This is explained partly by the difficulty in collecting field data to validate and compare with modeled and experimental results. This thesis describes the estuarine circulation and fine sediment transport associated with a sub-glacial freshwater discharge in a glacial fjord through simplified numerical simulations. Results showed that the discharge of freshwater underneath a glacier into an idealized fjord induces an estuarine-like circulation which is dynamically unstable in the near field, with gradient Richardson number at the sheared interface less than < 1 /4. The dilution factors and velocities of the vertical and surface plumes are strongly and nonlinearly related to the Froude number. The buoyancy flux primarily controls the resulting circulation with the momentum flux playing a secondary role. Fine sediment transport experiments showed that jet-dominated conditions are more sensitive to the presence of suspended sediment in the discharge than buoyancy-dominated conditions. At high concentrations, sediment settles in the far field, driven by convective sedimentation, and is transported back to the near field by the landward estuarine current. Convective sedimentation is triggered when density is increased by the higher sediment concentration at the interface between the upper and lower layer.
机译：已经提出，高纬度系统是全球变暖的后果日益明显的地区之一。从海洋学的角度来看，由于海冰形成和融化的季节动态以及潮水冰川输送的大量沉积物，冰川峡湾对气候变化特别敏感。但是，仅在过去的二十年中，我们对全球变暖背景下的峡湾动态的理解才是研究的主题。冰河峡湾是河口，其复杂性源于海底淡水排放（如浮力喷射）的结合，这是一种高度非静水的过程。尽管通过实验，数值研究和野外研究已经注意到与这些过程有关的浮力喷射和泥沙输送，但是对这些过程和冰川福特河口环流的综合研究却缺乏。部分原因是难以收集现场数据以验证并与建模和实验结果进行比较。本文通过简化的数值模拟描述了与冰川峡湾中亚冰川淡水排放有关的河口环流和细沙输送。结果表明，将冰川下面的淡水排入理想的峡湾会诱发类似河口的环流，该环流在近场中是动态不稳定的，剪切界面处的理查森数梯度小于<1/4。垂直羽和表面羽的稀释系数和速度与弗洛德数强烈且非线性相关。浮力通量主要控制所产生的循环，而动量通量起次要作用。精细的泥沙输送实验表明，与浮力为主的条件相比，射流为主的条件对排水中悬浮泥沙的存在更为敏感。在高浓度下，沉积物在对流沉积作用下沉积在远处，并通过陆上河口流运回近处。当上层和下层之间的界面上的较高沉积物浓度增加密度时，就会引发对流沉积。

著录项

  • 作者

    Salcedo-Castro, Julio.;

  • 作者单位

    Memorial University of Newfoundland (Canada).;

  • 授予单位 Memorial University of Newfoundland (Canada).;
  • 学科 Physical oceanography.
  • 学位 Ph.D.
  • 年度 2011
  • 页码 122 p.
  • 总页数 122
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 普通生物学;
  • 关键词

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