Along-isopycnal variability of spice in the North Pacific
Along-isopycnal variability of spice in the North Pacific
复制标题
北太平洋香料的沿等密度变化
DOI：
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
R. Pinkel
中科院分区：
文献类型：
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作者：
J. Klymak;W. Crawford;M. Alford;J. MacKinnon;R. Pinkel
介绍了阿拉斯加湾和北太平洋副热带环流的两次水文调查。这两次调查大致垂直于横向温度梯度，都是在夏季采集的，当时有浅层混合层和季节性温跃层。等轴线位移和水平速度主要由内波控制。沿等轴线的SPICE异常被检查以诊断侧向搅拌机制。沿近地表等参线的SPICE异常梯度谱大致服从∼kx0.6±0.2的幂规律(∼kx−1.4±0.2的方差谱幂规律)，并且在大多数情况下，谱随深度变红。近地表光谱可能与准地转湍流理论(考虑地面浮力效应时)的预测一致，但深部光谱与任何准地转理论不一致。SPICE梯度的概率分布在低梯度处表现出大的峰值，在大梯度处表现出长尾，表现为前锋的征兆。SPICE信号的垂直相干性随去相关深度尺度的变化而减弱，在10 0公里波长处的最大去相关深度尺度约为80m，并依赖于水平波长，其幂定律约为kx−1/2。横向去相关长度尺度为20-40公里，接近斜压Rossby半径。横向搅拌发生在大尺度上，平均横向位移在75m以上约200公里，更深处减少到100公里。统计数据的深度变化表明，示踪剂搅拌在每个等温线上的时间历史是重要的，或者存在未被考虑的深度相关的搅拌机制。
Two hydrographic surveys in the Gulf of Alaska and the North Pacific subtropical gyre are presented. Both surveys are roughly perpendicular to lateral temperature gradients, and were collected in the summer when there was a shallow mixed layer and a seasonal thermocline. Isopycnal displacements and horizontal velocities are dominated by internal waves. Spice anomalies along isopycnals are examined to diagnose lateral stirring mechanisms. The spectra of spice anomaly gradients along near-surface isopycnals roughly follow power laws of ∼kx0.6±0.2 (variance spectra power laws of ∼kx−1.4±0.2), and in most cases, the spectra become redder at depth. The near-surface spectra are possibly consistent with the predictions of quasi-geostrophic turbulence theory (when surface buoyancy effects are accounted for), but the spectra at depth are inconsistent with any quasi-geostrophic theory. Probability distributions of spice gradients exhibit a large peak at low gradients and long tails for large gradients, symptomatic of fronts. Vertical coherence of the spice signal falls off with a decorrelation depth scale that has a maximum of about 80 m at 100 km wavelengths and depends on horizontal wavelength with a power law of approximately kx−1/2. Lateral decorrelation length scales are 20–40 km, close to the baroclinic Rossby radius. Lateral stirring occurs over large scales, with average lateral displacements of about 200 km in the upper 75 m, decreasing to 100 km at greater depths. The depth variation of the statistics indicates that time history of tracer stirring on each isopycnal is important, or that there are unconsidered depth-dependent stirring mechanisms.