Timeline for How does a tsunami affect biology and other matter in its path while in deep water
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| Jul 6, 2015 at 15:08 | comment | added | milancurcic | -1 This answer is wrong. In an Eulerian framework, water particle has both horizontal and vertical non-zero velocity that averages to zero over the period of the wave. In a Lagrangian framework (following the wave particle), orbits are not closed and there is net movement of mass in the direction of the wave (Stokes drift). Vertical velocity averages to zero in a Lagrangian framework, but there exists a vertical pseudo-velocity due to divergence in the horizontal component of Stokes drift. | |
| Jul 5, 2015 at 23:37 | comment | added | Matt Hall | Sorry for another comment but I ran out of characters. I just wanted to add that the wavelength of tsunamis in deep water is indeed large, but the amplitude is not. I could edit the answer I guess, but given the other problem (see my other comment) I think I'll let Marc do it. | |
| Jul 5, 2015 at 23:34 | comment | added | Matt Hall | The bit about wave motion in this answer is wrong. Particle motion in a horizontally moving transverse wave is entirely vertical (so Simon W's remark is incorrect too). But ocean waves (including tsunamis) are not transverse waves. For one thing, fluids do not support transverse waves. Another clue to the sub-circular motion is in the withdrawal of the water before a tsunami. | |
| Jul 5, 2015 at 7:16 | comment | added | Semidiurnal Simon | As noted in other comments, this answer is wrong. Particle motion in a transverse wave follows an elliptical pattern, and I have no reason to think that a tsunami would be different. It is true that the net horizontal motion will be close to zero (but then again, so will the net vertical motion), but this does not mean there is no affect on the water column or the seabed. I imagine that there is little effect because, as noted, in deep water tsunamis have low amplitude - but I'm not expert enough to say this for sure. | |
| Jul 5, 2015 at 5:52 | comment | added | user4624937 | Interesting question and instructive answer! From what I understand of linear (sinusoidal) waves, the water particles may have a small non-zero instantaneous horizontal velocity (as part of the circular motion reddit referred to), but the net or average velocity is zero, as Marc Defant pointed out. | |
| Jul 5, 2015 at 5:49 | comment | added | @MarcDefant But if it is sinusoidal it makes me think even more strongly that the path should be circular/ellipsoidal (does not mean there is net forward transport). Wouldnt biology follow that orbital path as well? | ||
| Jul 4, 2015 at 21:22 | comment | added | see you | I think the confusion is how the wave is generated. A sinusoidal wave passing through water is not going to have a net horizontal movement (e.g., when a wave from a tsunami passes through water). However, waves generated by friction from wind blowing on the surface do generate some net horizontal movement. But your question relates to the affect of life in the oceans as a tsunami wave passes by. I tell my students that descriptions of tsunami's passing on the ocean under boats are rarely felt because the wavelength/amplitude is so huge. Basically life is unaffected. | |
| Jul 4, 2015 at 19:34 | comment | added | I thought that particles would move in a circular/ellipsoidal fashion like this upload.wikimedia.org/wikipedia/commons/8/8b/… | ||
| Jul 4, 2015 at 13:49 | history | answered | see you | CC BY-SA 3.0 |
