Tide-induced vertical mixing in the Laptev Sea coastal polynya
Tide-induced vertical mixing in the Laptev Sea coastal polynya
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DOI：
10.1029/2011jc006966
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发表时间：
2012-09
影响因子：
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通讯作者：
I. Dmitrenko;S. Kirillov;E. Bloshkina;Y. Lenn
中科院分区：
文献类型：
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作者：
I. Dmitrenko;S. Kirillov;E. Bloshkina;Y. Lenn
2008年4 - 5月和2009年4月，在拉普捷夫海陆架东部（~ 74°N, 128°E）的陆地快速冰缘系泊声学多普勒电流廓线仪（ADCP）和电导率-温度-深度（CTD）观测中，发现大陆架盐斜层（SHL）的半日带速度切变增强。2008年，月球半日日潮汐椭圆的主轴振幅在SHL中表现为11-13 m（15±3 cm/s）的中间最大值，在下层和近底层分别逐渐减小至~ 9±3 cm/s （7 m）和7±2 cm/s （19 m）。2009年，半日潮流表现出相似的趋势，但流速降低了约2倍。我们对梯度理查德森数的估计表明，与半日斜压潮汐流相关的速度切变可能足够强，足以在水团改变中发挥作用，促进切变不稳定性、湍流和跨SHL海水性质的垂直混合。这一结论与浅海中偶尔出现的接近均匀水层一致。2008年和2009年背景分层和局地潮汐动力学的差异，以及对冰湖开口的半日运动的快速响应，表明斜压潮是局地产生的。
Enhanced semidiurnal-band velocity shear across the shelf halocline layer (SHL) was found during land-fast ice edge mooring-based acoustic Doppler current profiler (ADCP) and conductivity-temperature-depth (CTD) observations over the eastern Laptev Sea shelf (∼74°N, 128°E) in April–May 2008 and April 2009. In 2008, the major axis amplitude for the lunar semidiurnal M2tidal ellipses demonstrated intermediate maximum in the SHL at 11–13 m (15 ± 3 cm/s), gradually decreasing to subice and near-bottom layers to ∼9 ± 3 cm/s (at 7 m) and 7 ± 2 cm/s (at 19 m), respectively. In 2009, the semidiurnal tidal flow exhibited similar patterns, but velocities were reduced by about factor of 2. Our estimates of gradient Richardson numbers suggest that the velocity shear associated with semidiurnal baroclinic tidal flow may be strong enough to play a role in water mass modification, promoting shear instabilities, turbulence, and vertical mixing of seawater properties across the SHL. This suggestion is consistent with near-homogeneous water layers episodically occurring in the SHL. Differences in the background stratification and local tidal dynamics between 2008 and 2009, together with rapid responses of the semidiurnal motion to polynya openings, suggest that the baroclinic tide is locally generated.