What are Amphidromic Points and how do they effect the ocean’s tides?

77 viewsOtherPlanetary Science

I’m researching how tides work as part of a book I’m writing, and I came across the term “Amphidromic Points” a couple of times. I did read through the Wikipedia page on them ([https://en.wikipedia.org/wiki/Amphidromic\_point](https://en.wikipedia.org/wiki/Amphidromic_point)) but there’s a lot of math involved that I didn’t quite understand.

Was curious if anyone here might be able to better explain it in layman’s terms?

In: Planetary Science

2 Answers

Anonymous 0 Comments

Tides are a bulge of water pulled by the moon and sun acting together.

If there was no land that bulge would just go around the earth

But because the world is not one ocean the bulge has to circulate

There’s a point that bulge revolves around and where there is no movement up and down from the tide

Anonymous 0 Comments

So, I’m just going off of the wikipedia article and my understanding of math and physics (associate’s degree in math, general-ed college physics). That said, I’ve never encountered this particular idea before, so I can’t provide anything deeper than what follows:

If you take a container of water, and shake it so that waves form; you will notice that some places in the container have big waves, and some don’t. If you get a different container of water, there will be different points. You will especially notice this if instead of shaking randomly, you shake the bottle in a circular motion: there will tend to be a point around which the water rotates; and that point will tend to have very small change in height from your shaking.

The oceans are a really big container of water; and the sun and moon shake that container through gravity. The result are the tides. However, the oceans are also shaken some by the Coriolis Effect – the fact that the earth is a rotating sphere, and so the equator is rotating around the center faster than the poles. However, all of these forces tend to be circular; so the result is the same as when you shake your container in a circle: the tides circle around some points.

Those points are called “amphidromic points” (“around-flowing points”), because the tides flow around those points.