UNDERTOW, RIP TIDE OR "RIP CURRENT".
UNDERTOW, RIP TIDE OR "RIP CURRENT".
复制标题
暗流、激流或“激流”。
DOI：
10.1126/science.84.2173.181
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发表时间：
1936
期刊：
影响因子：
56.9
通讯作者：
F. P. Shepard
中科院分区：
文献类型：
--
作者：
F. P. Shepard
讨论暗流、激流或“激流”地质书籍中关于海洋的讨论似乎特别集中在那些过时的科学教条上。在前一篇文章中，作者提请注意其中的几个谬论。其中可能包括所谓的“暗流”。对暗流的普遍理解，显然是来自于惊慌失措的冲浪者，但已被普遍接受，即水被海浪或风从海面上卷进来，然后回流到海底，形成一股强大的水流，在当地足以把人带到海底或出海。1925年，戴维斯对这一观点提出了挑战，他非常正确地指出，波浪使水面和底部的水在波峰时向前涌动，在波谷时向后涌动，这样，在海浪中的人就会交替地向前和向后涌动。然而，他认为，一定有一种水下回流的水流被岸上的风推到了口袋海滩上。戴维斯要求其他人写下他们可能与这个主题有关的经历。接下来的一系列简短的笔记一定让读者犹豫不决，不知道该相信什么。三位作家描述了他们所经历的水流，这些水流把他们带向大海的速度比他们游向陆地的速度要快，尽管水流主要是一种海面现象。另一位作家在观察的基础上同意戴维斯的观点，认为暗流是神话，而另一位作家则为旧观念提供了理论支持。另一方面，美国陆军工程师对海滩外海水沿底部运动的测量表明，海水以戴维斯所描述的方式沿底部进出。它以一种强烈而迅速的波动进入，以一种漫长而缓慢的运动离开。本文作者首先通过与洛杉矶救生员队长塞西尔·尼科尔斯先生的谈话，对这个问题有所了解。尼科尔斯讲述了他在加州威尼斯海滩上所谓的“激流”，他说，这些激流经常把游泳者卷到水深之外。对这些“激流”的研究表明，它们是沿着笔直的海滩向外移动的窄水带，几乎与海岸成直角。它们的间距为200码或更多，并延伸到半英里的距离。这些海流是在平静和有陆上风的情况下观察到的。它们可以很容易地区分，因为它们有翻腾的水和泡沫，1 SCIENCE, 78: 406-408, 1933。[2]杨建军，中国科学：地球科学，26(1):626,2005。3 w。C.琼斯，科学，61:444,1925；华莱士克雷格，I.布兰特，MP海特和WM戴维斯，科学，62:30-33,1925；[j] .中国科学：地球科学，2003,31(1):1 - 4。4 .队长LH休伊特，个人沟通。我们向外移动，在某种程度上干扰了进来的断路器。事实证明，这些电流的持续时间相当短，通常持续几分钟，并在同一或不同的位置重新发展。通过在“激流”中游泳，人们发现它们在海底和在海面上都至少有一定的速度。在一个案例中，人们发现底部有一个沿着持续的“激流”轴线的凹陷，深度约为一英尺。在电流的外部部分发现了一个漩涡运动。从划艇上看，激流的终点及其边缘边界非常明显，这既是因为流动的水，也是因为水中悬浮的沉积物。
DISCUSSIONUNDERTOW, RIP TIDE OR" RIP CURRENT" THE outworn dogmas of science seem to be par-ticularly concentrated in the discussions of theocean in geology books. In a previous note the writer called attention to several of these fallacies.'Among them could have been included the so-called" undertow." The common conception of the undertow, which comes evidently from panicky surf bathers, but has been commonly accepted, is that water is carried in along the surface by the waves or the wind and returns underneath, developing a current which may be strong enough locally to carry people under and out to sea. In 1925 Davis2 challenged this ie pointing out quite correctly that a wave causes the water to surge forward at the crest and backward in the trough both at the surface and on the bottom so that a person in the surf is alternately carried forward and backward. He suggested, however, that there must be a subsurface return of the water pushed into a pocket beach by an onshore wind. Davis requested others to write of their experiences which might bear on the subject. The series of short notes which followed must have left readers undecided as to what they should believe. Three writers3 described currents which they had experienced which carried them seaward faster than they could swim toward land, although the currentwas largely a surface phenomenon. Another writer on the basis of observations agreed with Davis that the undertow was mythical, while still another gave theoretical support for the old conception. On the other hand, measurement by U. S. Army engineers4 of the movement of water along the bottom outside the beach showed that the water moves in and out along the bottom in the manner described by Davis. It comes in with a strong, quick surge and goes out with a long, slower movement. The present writer first obtained some light on the question through conversationswith Mr. Cecil Nichols, head of the Los Angeles life-guards. Mr. Nichols told of what he called" rip-tides" alongthe beach at Venice, California, whichhe said frequently carried out bathers beyond their depth. Examination of these" rip-tides" showed that they are narrow bands of water moving outward almost at right angles to shore along straight stretches of beach. They are spaced at distances of 200 yards or more and extend out for distances up to half a mile. These currents were observed both under conditions of calm and with an onshore wind. They could be distinguished easily because of the zones of roiled water and foam which 1 SCIENCE, 78: 406-408, 1933. 2 WM Davis, SCIENCE, 61: 206, 1925. 3W. C. Jones, SCIENCE, 61: 444, 1925; Wallace Craig, I. Brant, MP Hite and WM Davis, SCIENCE, 62: 30-33, 1925; TT Quirke, SCIENCE, 61: 468, 1925. 4 Captain LH Hewitt, personal communication. were moving out and interfering to some extent with the incoming breakers. These currents proved to be of rather short duration, lasting several minutes as a rule and redeveloping either at the same or in a different location.By swimming in the" rip-tides" it was found that they have at least some velocity at the bottom as well as that which is so observable at thesurface. In one case thebottom was found to contain a depression about a foot in depth along the axis of a persistent" rip-tide." In the outer portion of the current an eddying motion was found. The terminus of the" rip-tide" as well as its marginal boundaries were seen from a row-boat to be very distinct both because of the moving water and because of the suspended sediment in the water.