# Why the range in tidal range? **URL:** \ **Category:** Factual Questions\ **Created:** [August 5, 2010, 9:22pm UTC](https://boards.straightdope.com/t/why-the-range-in-tidal-range/549332 "2010-08-05T21:22:15Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [August 5, 2010, 9:22pm UTC](https://boards.straightdope.com/t/why-the-range-in-tidal-range/549332/1 "2010-08-05T21:22:15Z")
[Tidal Range.](http://en.wikipedia.org/wiki/Tidal_range) The vertical difference between high and low tide ranges greatly, from nothing, to a few feet in open ocean, to 30 - 40 feet in some locations, including along the English Channel. Why? It does not seem to be an exclusive issue of latitude … so what is it? ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [August 5, 2010, 9:32pm UTC](https://boards.straightdope.com/t/why-the-range-in-tidal-range/549332/2 "2010-08-05T21:32:17Z")
It depends largely on the conformation of the coast. Here in Panama, we get tides of up to 18 feet on the Pacific side in the semi-enclosed Gulf of Panama. Only 50 miles away on the Caribbean coast, which is more open, the tides are only about 2 feet. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [August 5, 2010, 10:00pm UTC](https://boards.straightdope.com/t/why-the-range-in-tidal-range/549332/3 "2010-08-05T22:00:55Z")
So it is a funnel effect? ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [August 5, 2010, 10:07pm UTC](https://boards.straightdope.com/t/why-the-range-in-tidal-range/549332/4 "2010-08-05T22:07:11Z")
> [@DSeid](#): > > So it is a funnel effect? I believe that has a lot to do with it. The highest tides are in the Bay of Fundy, which narrows very strongly along its length. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [August 5, 2010, 10:11pm UTC](https://boards.straightdope.com/t/why-the-range-in-tidal-range/549332/5 "2010-08-05T22:11:40Z")
This [NOAA](http://www.co-ops.nos.noaa.gov/faq2.html) page linked to in the Wiki article gives more info: > [@](#): > > The tidal range of a particular location is dependent less on it position north/south of the equator than on other physcial factors in the area; topography, water depth, shoreline configuration, size of the ocean basin, and others. For example, let’s consider the southern coast of Alaska and British Columbia. The configuration of this coastline is very similar to a funnel, with the narrow end at Cook Inlet. The tides travel as a “wave” across the oceans, and in many other respects act as a “wave”; this type of configuration tends to accentuate the “wave” at the narrow end of the funnel. This is part of the reason for the large tidal ranges, 30+ feet, in the area of Cook Inlet. If you look at the tidal ranges for stations on the Bering Sea, outside this funnel but at the same latitude, you will find a tidal range of 5-7 feet. > > Another factor is the size of the ocean basin in which the tides are located. The Pacific Ocean is by far the largest of the world’s oceans. This means that the moon’s gravity has a large area of water to work on; therefore, its effect tends to be greater. Compare this to stations in the Baltic Sea. Many stations in the Baltic are as far north as any station in Alaska. However, due to the small size and shallow depth of the ocean basin, the tidal ranges in this area are relatively small. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [August 6, 2010, 1:31am UTC](https://boards.straightdope.com/t/why-the-range-in-tidal-range/549332/6 "2010-08-06T01:31:32Z")
Thank you. ---
**Author:** ![MikeF](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@MikeF](https://boards.straightdope.com/u/MikeF)\ **Post date:** [August 6, 2010, 2:38pm UTC](https://boards.straightdope.com/t/why-the-range-in-tidal-range/549332/7 "2010-08-06T14:38:43Z")
I’m heading for the Bay of Fundy in a couple of weeks. We’re going to ride the “tidal bore” a wave that forms as the incoming tide opposes the out flowing river. Apparently, it can get pretty rough as the bore crosses sand bars and such. Looks like fun in a Zodiac. ---
**Author:** ![Surly\_Chick](https://avatars.discourse-cdn.com/v4/letter/s/ec9cab/32.png) [@Surly\_Chick](https://boards.straightdope.com/u/Surly_Chick)\ **Post date:** [August 6, 2010, 2:44pm UTC](https://boards.straightdope.com/t/why-the-range-in-tidal-range/549332/8 "2010-08-06T14:44:42Z")
> [@MikeF](#): > > I’m heading for the Bay of Fundy in a couple of weeks. We’re going to ride the “tidal bore” a wave that forms as the incoming tide opposes the out flowing river. Apparently, it can get pretty rough as the bore crosses sand bars and such. Looks like fun in a Zodiac. Wear a flotation device. I’ve seen that on TV and it looks pretty scary. ---
**Author:** ![tr0psn4j](https://avatars.discourse-cdn.com/v4/letter/t/958977/32.png) [@tr0psn4j](https://boards.straightdope.com/u/tr0psn4j)\ **Post date:** [August 6, 2010, 4:40pm UTC](https://boards.straightdope.com/t/why-the-range-in-tidal-range/549332/9 "2010-08-06T16:40:54Z")
I don’t think I’ve ever seen a 8’ high tide here in Southern California. When I was in Southeast Alaska, their high tides were over 20’! ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 6, 2010, 5:30pm UTC](https://boards.straightdope.com/t/why-the-range-in-tidal-range/549332/10 "2010-08-06T17:30:31Z")
I suspect that you can get resonance issues, too, if a particular bay just happens to have a resonant frequency of 2/day for standing waves. ---
**Author:** ![Skammer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/skammer/32/143_2.png) [@Skammer](https://boards.straightdope.com/u/Skammer)\ **Post date:** [August 6, 2010, 5:50pm UTC](https://boards.straightdope.com/t/why-the-range-in-tidal-range/549332/11 "2010-08-06T17:50:22Z")
> [@MikeF](#): > > I’m heading for the Bay of Fundy in a couple of weeks. We’re going to ride the “tidal bore” a wave that forms as the incoming tide opposes the out flowing river. Apparently, it can get pretty rough as the bore crosses sand bars and such. Looks like fun in a Zodiac. We spent some time on the Bay of Fundy on our honeymoon, although I couldn’t get my bride to try rafting on the tidal bore. The tides are amazing, though - you can walk along the wharf at Digby and the boats are all up next to the docks, and then 12 hours later come back and they are literally sitting in the mud on the floor of the harbor eighteen feet below. [Here’s a picture](http://upload.wikimedia.org/wikipedia/commons/5/54/Bay_of_Fundy.jpg), although it looks like the image on the left is not full high tide. ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [August 7, 2010, 1:08pm UTC](https://boards.straightdope.com/t/why-the-range-in-tidal-range/549332/12 "2010-08-07T13:08:59Z")
Like Chronos suspects, tides much larger than open ocean tides result from resonance, as I read. That is, it’s not so much a funnel as it is a figurative bathtub whose sloshing frequency is close to the frequency of the tides. It helps if the bathtub is also shaped to not dissipate sloshing, or in other words to resonate with a high Q. I think if you could dig a long channel that ran east to west, whose bottom profile in the east-west direction was a chord of a circle, and whose walls were straight and parallel and smooth, and you made its length right to resonate at 6 hours (or whatever the tidal frequency is), you’d maximize the tide.