In dimictic lakes, the stable density stratification during summer and winter inhibits vertical mixing of nutrients and oxygen. This favors the development of hypolimnetic hypoxia, which degrades cool-water fish habitat and enhances nutrient mineralization from the sediments. Fall and spring turnover events, therefore, provide a crucial biannual link between surface and bottom waters. However, the physical processes occurring to mix lakes during turnover events remain comparatively uninvestigated. In this study, long-term field observations were supplemented with output from a three-dimensional numerical model, to better understand turnover events within a small temperate lake during 2011–2017. Mid-basin penetrative convection, sidearm convection, and wind-induced mixing were identified, with mid-basin convection likely contributing the most to turnover events; a typical side-arm convective plume had 2% (spring) to 4% (fall) of the mass flux compared to those at mid-basin. During fall turnover, wind shear only mixed the upper 35% of the surface mixed layer, with convection acting to deepen below. During spring turnover, ice-cover sheltered the lake from wind, causing convection to be the only process occurring and lengthening the turnover duration (~ 51 d) compared to fall (~ 13 d).

中文翻译：

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加拿大小盾湖的营业额

在双混晶湖中，夏季和冬季稳定的密度分层抑制了营养物质和氧气的垂直混合。这有利于低温缺氧的发展，这会降低冷水鱼类的栖息地并增强沉积物中的养分矿化。因此，秋季和春季的周转事件在地表水和底水之间提供了重要的两年一次的联系。然而，在周转事件期间发生混合湖泊的物理过程仍然相对未经调查。在这项研究中，长期实地观察补充了三维数值模型的输出，以更好地了解 2011-2017 年间温带小湖内的周转事件。确定了盆地中部穿透对流、侧臂对流和风致混合，盆地中部的对流可能对周转事件的贡献最大；与盆地中部相比，典型的侧臂对流羽流的质量通量为 2%（春季）至 4%（秋季）。在秋季周转期间，风切变只混合了表层混合层的上部 35%，对流作用在下面加深。在春季周转期间，冰盖为湖面遮风挡雨，导致对流是唯一发生的过程，与秋季（~13 天）相比，周转持续时间（~51 天）延长。