Observations of the principal tidal currents at Drake Passage
Observations of the principal tidal currents at Drake Passage
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德雷克海峡主要潮流的观测
DOI：
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发表时间：
1982
期刊：
影响因子：
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通讯作者：
R. Pillsbury
中科院分区：
文献类型：
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作者：
W. Nowlin;J. Bottero;R. Pillsbury
本文利用德雷克海峡12个测点的21条长流记录，描述了大西洋和太平洋之间该海域的主要全日（K_1和0_1）和半日（M_2和S_2）分潮。在北方海峡，潮汐主要为半日潮，在其他位置，潮汐为混合型。四分之一的波动动能的记录之间的周期为2小时和2天。大约50%的能量包含在以周日和半日频率为中心的两个窄带中（半日带也包含重要的惯性流能量）;这些带中的能量部分向南增加，从39%增加到66%。导纳计算表明，平均56%的带通动能与潮汐强迫势是一致的。最小二乘拟合（循环下降的方法）的250天的记录在10个最有活力的短期潮汐频率产生电流基本一致的潮汐强迫功能。从这些适合的平均分割相干潮汐能之间的四个主要潮汐成分的估计：75%在M2，16%在S2，9%在K1，和3%在01。这四个潮汐的平均潮汐椭圆构造的拟合和用于描述整个通道的深度和纬度变化，并在1975年，1976年和1977年之间进行比较。在深水中，相干全日潮的方差向南增加，而相干半日潮的方差在中途最小，并且向北增加比向南增加更多。的非相干（残留）部分的带通电流是各向同性的，在对比的相干成分，这是最有活力的通过（沿电流）方向。一般而言，这些非相干振荡在水深范围和最大静稳度的位置处能量最大。从最小二乘拟合得到的主轴分量之间的平方相干性和相位关系显示，K1，M2和S2潮汐传播与向南的组件，而01有一个向北的组件传播整个德雷克海峡。在同一系泊上垂直分离的海流计之间的一致性对于昼夜潮汐K1是最大的。时间变化的潮汐描述的时间序列的速端曲线和动能密度的电流在狭窄的通带集中的四个主要的潮汐成分。
Twenty-one long current records collected at 12 positions in Drake Passage are used to describe the principal diurnal (K1 and 01) and semidiurnal (M2 and S2) tidal current constituents in that region between the Atlantic and Pacific Oceans. The tide is predominantly semidiurnal in the northern passage and of mixed type at other locations. One-quarter of the fluctuation kinetic energy of the records is between periods of 2 hours and 2 days. Approximately 50% of that energy is contained in two narrow bands centered at the diurnal and semidiurnal frequencies (the semidiurnal band also contains significant inertial current energy); the fraction of energy in these bands increases southward across Drake Passage from 39 to 66%. Admittance calculations show that an average of 56% of this band-passed kinetic energy is coherent with the tidal forcing potential. Least square fitting (by the method of cyclic descent) of 250-day records at the 10 most energetic short-term tidal frequencies yields currents essentially coherent with the tidal forcing functions. From these fits the average partitioning of coherent tidal energy among the four principal tidal constituents is estimated: 75% at M2, 16% at S2, 9% at K1, and 3% at 01. Mean tidal ellipses for these four tides are constructed from the fits and used to describe depth and latitudinal variation across the passage and to make comparisons between the years 1975, 1976, and 1977. The variances of coherent diurnal tides in the deep water increase southward, whereas those for coherent semidiurnal tides are smallest in midpassage and increase more to the north than to the south. The noncoherent (residual) portions of the band-passed currents are isotropic, in contrast to the coherent constituents, which are most energetic in the through-passage (along-current) direction. In general, these non-coherent oscillations are most energetic for depth ranges and locations of greatest hydrostatic stability. The squared coherence and phase relationships between principal axis components obtained from the least square fits showed the K1, M2, and S2 tides to propagate with southward components while the 01 has a northward component of propagation across Drake Passage. Coherence between current meters separated vertically on the same mooring was greatest for the diurnal tide K1. Temporal variability of the tides is described by time series of hodographs and of kinetic energy density of currents in narrow pass bands centered on the four major tidal constituents.