Modeling deep-water renewal in Lake Baikal
Modeling deep-water renewal in Lake Baikal
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贝加尔湖深水更新建模
DOI：
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发表时间：
1996
期刊：
影响因子：
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通讯作者：
R. Matear
中科院分区：
文献类型：
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作者：
P. Killworth;E. Carmack;R. Weiss;R. Matear
温度，溶解氧，营养物质，和从贝加尔湖获得的氯氟烃- 12数据被用来描述在一个深，温带湖泊的深水更新。观测结果被用来提出对流的物理机制，并制定了一个模型的深层通风。控制深水更新的关键物理机制是所谓的温压不稳定性。由于最大密度的温度随深度而降低，如果冷混合层的底部移动到其温度与最大密度的局部温度相匹配的深度，则湖泊可能会变得有条件地不稳定，从而导致下沉羽流。这种现象的一个重要后果是，像贝加尔湖这样的深层温带湖泊并不是每年两次完全混合;相反，深层通风是间歇性的。一个二维模型的风和浮力驱动的湖泊显示了许多强大的混合事件和一个相当现实的季节性周期，表明该假设是物理上可实现的。一个填充箱模型是用来推导出所需的年平均通量，以产生一个稳定的垂直分布的示踪剂观测。该模型对氧和氯氟烃的分布拟合良好。世界上大约50%的液态淡水存在于位于北纬-45到65度之间的温带地区的大型深湖中（见哈钦森，1957年）。对这些湖泊来说，最重要的是它们的通风时间，这是与深水更新相关的时间尺度，因为深对流过程最有力地控制了标量性质（如溶解氧、营养物和人为污染物）的内部再分布（见Wiiest等人，1988年）。然而，令人惊讶的是，很少有人尝试研究和量化深呼吸通气。
Temperature, dissolved oxygen, nutrients, and chlorofluorocarbon- 12 data obtained from Lake Baikal are used to describe deep-water renewal in a deep, temperate-latitude lake. Observations are used to propose the physical mechanism governing convection and to formulate a model of deep ventilation. The key physical mechanism governing deep-water renewal is the so-called thermobaric instability. Because the temperature of maximum density decreases with depth, a lake can become conditionally unstable if the base of the cold mixed layer is displaced to a depth at which its temperature matches the local temperature of maximum density, thereby resulting in sinking plumes. An important consequence of this phenomenon is that deep temperate lakes such as Baikal do not completely mix twice yearly; instead, deep ventilation is episodic. A two-dimensional model of a wind- and buoyancy-driven lake shows many strong mixing events and a fairly realistic seasonal cycle, indicating that the hypothesis is physically realizable. A filling-box model is used to deduce the annually averaged fluxes necessary to produce a steady vertical distribution of tracers as observed. Good fits are obtained to oxygen and chlorofluorocarbon distributions by this model. About 50% of the world’s liquid freshwater is contained in the large deep lakes located in the temperate latitudes between -45 and 65”N (see Hutchinson 1957). Of fundamental importance to such lakes is their ventilation time, the time scale associated with renewal of deep water, for it is the deep convection process that most strongly controls the internal redistribution of scalar properties such as dissolved oxygen, nutrients, and anthropogenic pollutants (see Wiiest et al. 1988). However, surprisingly few attempts to study and quantify ventilation in deep