The circulation and residence time of the strait of Georgia using a simple mixing‐box approach
The circulation and residence time of the strait of Georgia using a simple mixing‐box approach
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DOI：
10.3137/ao.450401
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发表时间：
2007-12
期刊：
影响因子：
1.2
通讯作者：
R. Pawlowicz;O. Riche;M. Halverson
中科院分区：
文献类型：
--
作者：
R. Pawlowicz;O. Riche;M. Halverson
加拿大不列颠哥伦比亚省佐治亚州海峡的新观测表明，温度和溶解氧具有明显的季节性周期，具有空间变化的相位。振荡系统中的相滞后是由内部时间尺度引起的，在流体系统中可以解释为停留时间。在开发阶段，我们将这一水体划分为四个区域：弗雷泽河羽流、50m以下的地表水、200m以下的中游水域和深水，建立了一个定量的、内部一致的循环方案。在该方案中，中水是体积最大的区域，不断更新，其特性随着源水特性的不断变化而变化。河口环流对淡水流入变化的依赖性较弱。深水在体积上不那么重要，但海洋来源水密度的季节性变化可以通过驱动额外的流入而在整个环流中产生变化，从而导致深水更新和上升流增加。反过来，上升流的增加导致地表温度低于预期。中水停留时间约为160天。深水在夏季每年更新一次，在一年的其余时间只受垂直扩散的影响。整个海峡的地表水停留时间最多几个月，但弗雷泽河羽流的淡水停留时间约为1天。此外，我们还发现，由于哈罗海峡的大量再循环，海洋源水在海峡的停留时间为1.7年。这一方案的其他结果与对水平输送、海-气热通量、地下氧气(O2)利用率和初级生产量的独立估计一致。最后，对空间位相变化的分析表明，中间流入流以边界流的形式沿弗雷泽三角洲的斜坡进入海峡。
Abstract New observations in the Strait of Georgia, British Columbia, Canada show that temperature and dissolved oxygen have a pronounced seasonal cycle, with a spatially varying phase. Phase lags in oscillating systems arise due to internal time scales which can be interpreted in fluid systems as residence times. Exploiting phase we construct a quantitative and internally consistent circulation scheme for this body of water after dividing it into four regions: the Fraser River plume, the surface waters down to 50 m, the intermediate waters down to 200 m, and the deep water. In this scheme the intermediate water, the largest region by volume, is continually renewed, and its characteristics change in response to continuous changes in the characteristics of source waters. The dependence of the estuarine circulation on variations in fresh inflow is weak. The deep water is volumetrically less important, but seasonal changes in the density of oceanic source waters can produce a variation in the overall circulation by driving an additional inflow which leads to both deep renewal and increased upwelling. In turn, this increased upwelling results in lower surface temperatures than might otherwise be expected. Intermediate water residence times are about 160 days. Deep water is renewed once per year in summer and is affected only by vertical diffusion during the rest of the year. Surface water residence times for the entire Strait are a few months at most, but the Fraser River plume has a freshwater residence time of approximately 1 day. In addition, we find that the residence time of oceanic source waters in the Strait is 1.7 years due to a substantial recirculation in Haro Strait. Other consequences of this scheme are consistent with independent estimates of horizontal transports, air‐sea heat fluxes, subsurface oxygen (O2) utilization, and primary production. Finally, analysis of the spatial phase variations suggests that the intermediate inflow enters the Strait as a boundary current along the slopes of the Fraser delta.