We investigate the nearshore-offshore exchange of hypoxic waters during episodic coastal upwelling events in the nearshore waters of northern Lake Erie using intensive field observations and a validated hydrodynamic and water quality model. We observe wind-induced coastal upwelling events to be the dominant nearshore physical process in the lake which are energized every 5–10 days. When the winds were predominantly blowing from the west or south-west, epilimnetic waters were transported to the offshore bringing in hypolimnetic waters with low temperature (8–10 °C), dissolved oxygen (DO: 0–6 mg L⁻¹) and pH (6–7) to the nearshore zones. During these events, vertical diffusivity coefficients decreased from 10⁻² m² s⁻¹ to values as low as ~ 10⁻⁷ m² s⁻¹. In late summer, the coastal upwelling events in the nearshore waters lower the near bottom DO to hypoxic levels (DO < 2 mg L⁻¹). Lake-wide observations of DO and pH show that they are positively and linearly correlated while in the nearshore DO and pH experience spatial and temporal variability where upwelling events were developed, which were further assessed using a three-dimensional model. The model accuracy to reproduce offshore hypoxia was first assessed on a lake-wide basis using a coarse resolution model for a five-year period (2008–2012) and in nearshore waters using a higher resolution model for 2013. We use the model results to delineate the near bottom areas experiencing hypoxia at time scales longer than 48 h.

我们使用密集的野外观测以及经过验证的水动力和水质模型，调查了伊利湖北部近岸水域的沿海上升事件中近岸低氧水的近岸-近海交换。我们观察到风诱发的海岸上升事件是湖中主要的近岸物理过程，每5-10天就会通电。当主要从西风或西南风吹来时，上表层水运到近海，带来低温（8-10°C），溶解氧（DO：0-6 mg L ^-1）和pH值（6–7）到近岸区域。在这些事件中，垂直扩散系数从10 ^-2 m ² s ^-1减小值低至〜10 ^-7 m ² s ^-1。夏末，近岸水域的沿海上升事件将近底DO降至低氧水平（DO <2 mg L ^-1）。全湖对溶解氧和pH值的观察表明，它们之间呈线性正相关，而在近岸溶解氧和pH值发生时空变化时发生了上升流事件，并使用三维模型对其进行了进一步评估。首先，使用五年（2008-2012年）的粗分辨率模型在全湖范围内以及2013年使用高分辨率模型在近岸水域中，对重现近海缺氧的模型准确性进行了评估。在超过48小时的时间范围内描绘出发生缺氧的近底部区域。