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首页> 外文期刊>Aquatic Sciences >Preconditioning of an underflow during ice-breakup in a subarctic lake
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Preconditioning of an underflow during ice-breakup in a subarctic lake

机译：北极湖冰破裂过程中的底流预处理

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The fate of inflows into lakes has been exten sively studied during summer stratification but has seen relatively little focus during the weak winter stratification, with or without ice-cover. Field observations are presented of groundwater inflow into a shallow bay of a subarctic lake. Atmospheric forcing of the bay during the study period was extremely variable and coincided with spring ice-cover break-up. Two dominant wind regimes were identified; (1) weak wind-forcing (wind speed <5 m s~(-1) or land-fast ice-cover), and (2) strong wind-forcing (wind speed >5 m s~(-1) and open water). At a relatively constant temperature of ～3.3℃, the groundwater inflow was closer to the temperature of maximum density than the water in the main body of the lake, which during the observed winter stratification is ～ 1.2℃. During weak wind-forcing, the stratification within Silfra Bay approximated two-layers as this denser groundwater formed a negatively buoyant underflow. A calculated underflow entrainment rate of 2.8 × 10~(-3) agrees well with other underflow studies. During strong wind-forcing, the water column out to the mouth of the bay became weakly stratified as the underflow was entrained vertically by wind-stirring. Observed periods of mixing can be predicted to occur when turbulent kinetic energy (TKE) production by wind stirring integrated over the underflow hydraulic residence time in the bay exceeds the potential energy associated with the stratification. A decrease of ice cover, as observed in the studied subarctic lake over the last decade, will result in the underflow being more frequently exposed to the strong wind-forcing regime during winter, thereby altering the winter distribution of groundwater inflow within the lake.
机译：在夏季分层期间，对流入湖泊的命运进行了广泛的研究，但在薄弱的冬季分层（有无冰盖）中，关注的焦点相对较少。现场观察显示了地下水流入亚北极湖浅湾的情况。在研究期间，海湾的大气强迫变化很大，并且与春季冰盖破裂有关。确定了两个主要的风况； （1）弱风（风速<5 ms〜（-1）或陆地快速覆冰），和（2）强风（风速> 5 ms〜（-1）和开阔水域） 。在〜3.3℃的相对恒定温度下，地下水流入量比湖泊主体中的水更接近最大密度温度，在冬季观测到的冬季分层为〜1.2℃。在弱风作用下，Silfra湾内的分层大约为两层，因为该稠密的地下水形成了负浮力的底流。计算得出的底流夹带率为2.8×10〜（-3），与其他底流研究非常吻合。在强风作用下，由于潜流在垂直方向上被风的搅动带走，因此进入海湾口的水柱变得分层较弱。当在海湾中底流水力停留时间上通过风搅拌产生的湍动能（TKE）产生的动能超过与分层相关的势能时，可以预见到观察到的混合时间。在过去的十年中，在研究的北极湖中，冰盖的减少将导致底流在冬季更频繁地暴露于强风作用下，从而改变了湖水在冬季的分布。

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