Estuarine versus transient flow regimes in Juan de Fuca Strait
Estuarine versus transient flow regimes in Juan de Fuca Strait
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胡安德富卡海峡河口与瞬态水流状况
DOI：
10.1029/2006jc003925
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发表时间：
2007
影响因子：
--
通讯作者：
E. Kulikov
中科院分区：
文献类型：
--
作者：
R. Thomson;S. Mihaly;E. Kulikov
[1]观察到胡安德富卡海峡的残余流在两种基本状态之间切换：河口和瞬变。夏季盛行90%的时间和冬季55%的时间盛行于河口，具有两周一次的调制三层结构，其特征是60±15米以上的强(∼50 cm S−1)流入，60至125m深度的中等(∼25 cm S−1)流入，125±10 m以下的弱(∼10 cm S−1)流入。旋转使航道北侧上层深度增加40m，有利于上升流的沿海风使底层流入增加达5 cm S−1。旋转与东部海峡潮流混合对河口流的调制相结合，导致核心流区沿航道速度和跨航道位置的双周变化。夏季约有10%的时间发生瞬变流动，冬季约有45%的时间发生瞬变流动，这种流动正在迅速演变，在外海岸的极地风事件期间产生的河口环流在水平和垂直方向上都发生了切变。重大事件可持续数周，迫使净向内输送，并产生沿海峡南部(奥林匹克半岛)边界的O(10)公里宽、表面强化的O(100)厘米S−1流入。这种“奥林匹克半岛逆流”通常伴随着盐度的突然下降，表明这是一种起源于华盛顿大陆架北部低密度水的浮力流。
[1] Residual currents in Juan de Fuca Strait are observed to switch between two fundamental states: estuarine and transient. The estuarine regime, which prevails roughly 90% of the time in summer and 55% of the time in winter, has a fortnightly modulated, three-layer structure characterized by strong (∼50 cm s−1) outflow above 60 ± 15 m depth, moderate (∼25 cm s−1) inflow between 60 and 125 m depth, and weak (∼10 cm s−1) inflow below 125 ± 10 m depth. Rotation increases the upper layer depth by 40 m on the northern side of the channel and upwelling-favorable coastal winds augment inflow in the bottom layer by as much as 5 cm s−1. Rotation, combined with modulation of the estuarine currents by tidal mixing in the eastern strait, leads to fortnightly variability in the along-channel velocity and cross-channel positioning of the core flow regions. Transient flows, which occur roughly 10% of the time in summer and 45% of the time in winter, are rapidly evolving, horizontally and vertically sheared “reversals” in the estuarine circulation generated during poleward wind events along the outer coast. Major events can persist for several weeks, force a net inward transport, and give rise to an O(10) km wide, surface-intensified, O(100) cm s−1 inflow along the southern (Olympic Peninsula) boundary of the strait. This “Olympic Peninsula Countercurrent” is typically accompanied by an abrupt decrease in salinity, indicating that it is a buoyancy flow originating with low-density water on the northern Washington shelf.