Turbulent mixing and heat fluxes under lake ice: the role of seiche oscillations
Turbulent mixing and heat fluxes under lake ice: the role of seiche oscillations
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DOI：
10.5194/hess-22-6493-2018
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发表时间：
2018-12-14
影响因子：
6.3
通讯作者：
Lindgren, Elisa
中科院分区：
文献类型：
--
作者：
Kirillin, Georgiy;Aslamov, Ilya;Lindgren, Elisa
我们进行了一个实地研究的混合和垂直热量输送下的冰盖的北极湖泊。混合强度估计从小尺度振荡的水温和湍流动能耗散率来自当前的速度波动。在将冰基与较温暖的深水沃茨分开的稳定分层界面层中，普遍存在着发展良好的湍流条件。湍流混合的来源被确定为整个湖泊（正压）振荡的水体驱动的强风事件在冰面上。我们推导出一个缩放的冰水热通量耗散Kolmogorov尺度的基础上，并成功地测试对测量的耗散率和冰下温度梯度。结果抛弃了传统的假设，近传导热输运内的分层冰下层，并建议到冰盖融化的基础热通量的贡献是高于通常假设。北极季节性冰盖的减少目前正被公认为气候变化的一个主要指标。在控制季节冰生长和融化的机制中，冰-水界面处的热传递仍然是研究最少的。研究结果可应用于内陆和沿海沃茨季节性冰的热收支。
We performed a field study on mixing and vertical heat transport under the ice cover of an Arctic lake. Mixing intensities were estimated from small-scale oscillations of water temperature and turbulent kinetic energy dissipation rates derived from current velocity fluctuations. Well-developed turbulent conditions prevailed in the stably stratified interfacial layer separating the ice base from the warmer deep waters. The source of turbulent mixing was identified as whole-lake (barotropic) oscillations of the water body driven by strong wind events over the ice surface. We derive a scaling of ice-water heat flux based on dissipative Kolmogorov scales and successfully tested against measured dissipation rates and under-ice temperature gradients. The results discard the conventional assumption of nearly conductive heat transport within the stratified under-ice layer and suggest contribution of the basal heat flux into the melt of ice cover is higher than commonly assumed. Decline of the seasonal ice cover in the Arctic is currently gaining recognition as a major indicator of climate change. The heat transfer at the ice-water interface remains the least studied among the mechanisms governing the growth and melting of seasonal ice. The outcomes of the study find application in the heat budget of seasonal ice on inland and coastal waters.