On dynamics and mixing of inflowing saltwater in the Arkona Sea
On dynamics and mixing of inflowing saltwater in the Arkona Sea
复制标题
阿科纳海流入盐水的动力学和混合
DOI：
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
V. Mohrholz
中科院分区：
文献类型：
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作者：
H. Lass;V. Mohrholz
[1]在1998/1999年和1999/2000年冬季期间，对Arkona盆地的窗台和边缘的温度、盐度和海流进行了时间序列测量，并对整个Arkona盆地的分层和海流进行了船基测量。在平均深度为30 m处，盐跃层将混合良好的微咸水表面与分层的咸水底层水分开。含盐底层水被包含在一个高达15米厚的水池中，充满了Arkona盆地的中部。这种分层导致了6 km宽的Rossby半径和0.7 m/s的相速度的第一斜压模式。平均层结的扰动气旋性地转涡旋的特征半径等于第一斜压Rossby半径和上升和下降过程中的海岸边界层。垂直流剖面的90%的变异性可由第一和第二阶矩描述。目前的配置文件的最显着的特点是存在的埃克曼底部摩擦层中发现的两种模式。正压模态的Ekman层厚度为10-15 m，斜压模态的Ekman层厚度约为5 m。斜压环流由底层的脉动气旋运动和上层的反气旋运动组成，沿着Arkona盆地的边缘，由含盐底层水溢出窗台进入Arkona盆地。含盐的底层水作为重力流从岩床流入Arkona盆地，该盆地在重力和科里奥利力的作用下处于一级平衡状态，而摩擦力小于其他两种力。摩擦力迫使一个螺旋运动进入Arkona盆地的中心，在那里它促成了密集的底部水池。密集底层水的前锋在西风带边缘以约30 cm/s的相速度移动，并沿Arkona盆地的南缘和东缘沿着减慢至约10 cm/s。有证据表明，密集的底层水羽与周围的水混合的风引起的夹带在附近的窗台。传播的盐水羽流的主要混合机制是通过差异平流将其前缘前的水与前缘后的底层水混合。
[1] Time series measurements of temperature, salinity and current at the sills and the rim of the Arkona Basin have been performed during the winter seasons 1998/1999 and 1999/2000 together with ship-based measurements of stratification and currents covering the whole Arkona Basin. The well-mixed brackish surface was separated from the stratified saline bottom water by a halocline at a mean depth of 30 m. The saline bottom water was contained in an up to 15 m thick pool filling the central part of the Arkona Basin. This stratification resulted in a 6 km wide Rossby radius and a phase velocity of 0.7 m/s for the first baroclinic mode. The mean stratification was disturbed by cyclonic geostrophic eddies with a characteristic radius equal to the first baroclinic Rossby radius and up- and downwelling processes in the coastal boundary layer. 90% of the variability of the vertical current profile can be described by the first and second EOF. The most pronounced feature of the current profile is the existence of an Ekman bottom friction layer found in both modes. The thickness of the Ekman layer of the barotropic mode is 10–15 m and that of the baroclinic mode is about 5m. The baroclinic circulation consists of a pulsating cyclonic motion in the bottom layer and an anticyclonic motion in the upper layer along the rim of the Arkona Basin, driven by the spilling of saline bottom water over the sills into the Arkona Basin. The saline bottom water is flowing as gravity current from the sills into the Arkona Basin which is in a first order balanced by gravity and the Coriolis force, whereas friction is smaller than the other two forces involved. The friction imposes a spiral motion into the center of the Arkona Basin where it contributes to the dense bottom water pool. The front of the dense bottom water moves with a phase speed of about 30 cm/s at the westerly rim and slows down to about 10 cm/s along the southerly and easterly rim of the Arkona Basin. Evidence was found that the dense bottom water plume mixes with the ambient water by wind induced entrainment in the vicinity of the sill. The main mixing mechanism of a propagating saltwater plume is mixing of the water ahead of its front with the bottom water behind the front by differential advection.