A realistic numerical model is used to study the circulation and mixing of the Salish Sea, a large, complex estuarine system on the United States and Canadian west coast. The Salish Sea is biologically productive and supports many important fisheries but is threatened by recurrent hypoxia and ocean acidification, so a clear understanding of its circulation patterns and residence times is of value. The estuarine exchange flow is quantified at 39 sections over 3 years (2017–2019) using the Total Exchange Flow method. Vertical mixing in the 37 segments between sections is quantified as opposing vertical transports: the efflux and reflux. Efflux refers to the rate at which deep, landward‐flowing water is mixed up to become part of the shallow, seaward‐flowing layer. Similarly, reflux refers to the rate at which upper layer water is mixed down to form part of the landward inflow. These horizontal and vertical transports are used to create a box model to explore residence times in a number of different sub‐volumes, seasons, and years. Residence times from the box model are generally found to be longer than those based on simpler calculations of flushing time. The longer residence times are partly due to reflux, and partly due to incomplete tracer homogenization in sub‐volumes. The methods presented here are broadly applicable to other estuaries.

中文翻译：

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盐海中的河口环流，混合和停留时间

实际的数值模型用于研究Salish海（美国和加拿大西海岸的大型复杂河口系统）的环流和混合。萨利什海具有生物生产能力，并支持许多重要的渔业，但受到反复缺氧和海洋酸化的威胁，因此对它的环流方式和停留时间有一个清晰的了解是很有价值的。使用总交换流量方法，在3年（2017-2019年）的39个断面中，对河口交换流量进行了量化。在段之间的37个段中的垂直混合被量化为相反的垂直传输：外排和回流。外排是指将深层的向岸流动的水混合成浅层的，向海流动的层的速率。相似地，回流是指上层水向下混合形成部分陆上入流的速率。这些水平和垂直运输用于创建盒子模型，以探索在许多不同子体积，季节和年份中的停留时间。通常发现，基于盒式模型的停留时间比基于更简单的冲洗时间计算的停留时间更长。较长的停留时间部分归因于回流，部分归因于子体积中示踪剂均化不完全。这里介绍的方法广泛适用于其他河口。通常发现，基于盒式模型的停留时间比基于更简单的冲洗时间计算的停留时间更长。较长的停留时间部分归因于回流，部分归因于子体积中示踪剂均化不完全。这里介绍的方法广泛适用于其他河口。通常发现，基于盒式模型的停留时间比基于更简单的冲洗时间计算的停留时间更长。较长的停留时间部分归因于回流，部分归因于子体积中示踪剂均化不完全。这里介绍的方法广泛适用于其他河口。