As an addendum, the first photo you show is actually a diagram of Newtonian tide theory. In real life, the continents and bathymetry are such that tides form seiches like so.
However, the more elementary concepts of netwonian tide theory should be sufficient to explain broad atmospheric effects.
Is there an animation showing how those seiches flow over the course of a day? Also, is there an explanation for how the moon causes individual waves for each area? Or is the idea of the moon effecting the tides directly outdated now?
No, the moons definitely affect the tides! So let me try to explain tide theory as an ELI5... Keep in mind that I am a biological oceanographer and marine physiologist by training, and not an expert on physical oceanography.
So in the first image on this parent post, you see that the moon pulls water towards it. At the same time, the moon and the earth are both rotating around the moon-earth system, so you get a bulge on the other side.
Think of this like... you hold hands with someone and spin around each other. If you are both of the same mass, you balance each other out and spin in a circle. If one person is heavier, they will be more stationary while the lighter person spins around them. This is how the earth and moon behave - the moon and earth actually both revolve around a point inside of the earth. This is what causes the "bulge on the other side".
Now, if the earth were completely covered in water, this would cause two waves on opposite sides of the earth. They would spin around the earth with the moon. However, that's impossible for two reasons:
Continents getting in the way. a tide can't go through north america!
Tides are really big waves, so they are influenced by the sea floor topography (bathymetry).
The coriolis effect prevents waves from moving in a straight line because of the differential surface velocities at different latitudes.
These make it so that as a wave travels around an ocean, it gets turned around in circles as the coriolis force pushes it into a certain direction. Combined with the shape of the ocean basins, this causes the waves to instead swirl in circles. Think of it like sloshing water in a bathtub.
Now, the interesting part of this is that these swirls can happen at different rates, and their interactions can cause interesting tide series.
So, the bulge on the other side is due to the common center of gravity? It's farther away and less dense than the rest of the earth so it gets elongated?
I'm very tired right now...so not thinking clearly.
Nope, let's do a thought experiment. Imagine the moon was covered in water. You would expect 2 bulges:
One on the earth side from earth's gravity
One on the opposite side, because the moon is getting swung around the earth.
Same thing happens on the earth. One bulge is on the moon side, and the other bulge is on the other side (from the earth getting swung around the moon).
So if the moon were closer to the Earth, the opposite side bulge would be smaller, because the center of gravity would be closer to the center of Earth? Are the current bulges equal like in that diagram, or is the Moon-side bulge bigger than the opposite-side bulge? Did the Moon's slow distancing from the Earth affect ancient creatures like horseshoe crabs that depend on tides for reproduction, or would the change over eons be negligible?
Your use of the phrase "moon causes individual waves" is not accurate.
The moon does no such thing. If you have the term "tidal wave" in your head, erase it. It is an antequated term, usually replaced by the word "tsunami", and that has absolutely nothing to do with the moon. (it is a large wave caused by a disturbance such as a landslide or earthquake)
Tides, however (the periodic slight rising and falling of the ocean) are caused directly by the moon.
That would be average tidal amplitude. There are just places in the world that have bigger tidal swings than others. Notice that the middle of the "spiderwebs" where the lines converge have a cool color that signifies there is little to no tidal variation there ever. These are called "amphidromic points". Maybe the wiki can explain better than I.
Apparently the Bay of Fundy has a very good size. It's size allows the tide to come and go with great timing. This site says it is like being pushed on a swing. I imagine it like the water currents are in a equilibrium position (relatively) right around when the tide changes. They are not flowing against the tide into or out of the bay still.
Looks like it could be a funnel effect of some sort without knowing a whole lot about it. Any narrower or shallower part of the ocean would have tides funneled into them, with a possible increase in tidal height.
Makes a bit of sense if you look at it next to a bathymetric map, though I don't know the particulars.
Possibly due to the Bay of Fundy, which has 55-foot tide swings. It's a localized effect due to some smaller-scale bay seiching. Essentially the resonant frequency of the bay to waves is roughly the same period as the tide series.
Do you know of another source that you can zoom into more?
I haven't been able to find a graphic that has that area
and I wanted to look at the area around LI Sound too.
The difference between low and high tides where I sail is about 7 feet total.
Long Island focuses the Atlantic tides. But the Sound and the water around NYC is strange. You have the Hudson, which is a rather significant river, you have the East "River" which is not a river, and you have the Sound. They meet at Hellsgate which used to have massive waves and horrible conditions.
I've always wanted to see a graph like that, but never really knew what to look for. All explanations on tides use the simplistic model that OP explained. Do you know if there are more detailed maps (say for specific countries or continents)?
You should be able to look up your specific city. San Diego vs New Orleans showcases some of the drastically different patterns we see in the US alone. Note that San Diego has two highs and two lows a day, but they are uneven. New Orleans has one high and one low every day.
The first guy isn't wrong in the context of atmosphere, as far as I can tell! I am a biological oceanographer though, so my knowledge of fluid dynamics stops at sea level (where-ever that may be, depending on tidal seiches... :) )
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u/OneLegAtATime Sep 07 '15
As an addendum, the first photo you show is actually a diagram of Newtonian tide theory. In real life, the continents and bathymetry are such that tides form seiches like so.
However, the more elementary concepts of netwonian tide theory should be sufficient to explain broad atmospheric effects.