Semidiurnal Tides on the Laptev Sea Shelf with Implications for Shear and Vertical Mixing
Semidiurnal Tides on the Laptev Sea Shelf with Implications for Shear and Vertical Mixing
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DOI：
10.1175/jpo-d-12-0240.1
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发表时间：
2014-01-01
影响因子：
3.5
通讯作者：
Lenn, Yueng-Djern
中科院分区：
文献类型：
--
作者：
Janout, Markus A.;Lenn, Yueng-Djern
北极大陆架海拥有全球重要的淡水资源，影响着北冰洋的分层、环流和气候。这种淡水可以通过强烈的湍流动能耗散事件注入到表面混合层以下，正如Laptev海微观结构观测所证实的那样。潮汐提供了一种主要的能量来源，这种能量可以被消散，从而驱动拉普捷夫海的河床混合。来自大陆架各地点的多年ADCP系泊记录显示，半日潮主要由M-2和S-2组成，其中外大陆架的振幅最大。在大陆架的大部分地区，潮汐是顺时针极化的，并被分层剪切，这是M-2临界纬度附近的特征。内陆架潮汐和剪切结构的年际变化主要由分层背景下的勒拿河淡水羽流决定。在所有地点，海冰下的M-2潮汐增强，因此季节性冰盖的变化可能导致潮汐和水柱结构的变化。本研究的主要结论是：(1)相对于内陆架，潮汐在外陆架上的全年作用相对更大；（ii）海冰减少将全面降低海流的可预测性，特别是在内大陆架上；(3)淡水分布通过设置垂直潮汐结构直接影响河床混合。这些综合影响意味着，未来海冰的减少将增加淡水的变化性和垂直混合，特别是在内大陆架，即列拿河最初进入拉普捷夫海的地方。
The Arctic continental shelf seas hold a globally significant source of freshwater that impacts Arctic Ocean stratification, circulation, and climate. This freshwater can be injected below the surface mixed layer by intense turbulent kinetic energy dissipation events, as resolved by Laptev Sea microstructure observations. The tides provide a major source of energy that can be dissipated and hence drive diapycnal mixing in the Laptev Sea. Multiyear ADCP mooring records from locations across the shelf reveal that semidiurnal tides are dominated by the M-2 and S-2 constituents, with the largest amplitudes on the outer shelf. Throughout most of the shelf, tides are clockwise polarized and sheared by stratification, as characteristic near the M-2 critical latitude. Interannual variations of the tidal and shear structures on the inner shelf are mainly determined by the stratification-setting Lena River freshwater plume. In all locations, M-2 tides are enhanced under sea ice, and therefore changes in the seasonal ice cover may lead to changes in tides and water column structure. The main conclusions of this study are that (i) tides play a comparatively greater role year-round on the outer shelf relative to the inner shelf; (ii) a sea ice reduction will overall decrease the predictability of the currents, especially on the inner shelf; and (iii) the freshwater distribution directly impacts diapycnal mixing by setting the vertical tidal structure. These combined effects imply that future sea ice loss will increase the variability and vertical mixing of freshwater, particularly on the inner shelf, where the Lena River first enters the Laptev Sea.