Jump to content

Tides and Amphidromic points


Recommended Posts

.."the tides in French Pass can kill John Dories"..

& not just fishes by the sounds of it. I have been through that gap in a yacht - it looked scary even from the safety of big white floater, so I am not sure what would possess someone to actually jump in .

 

 

Link to post
Share on other sites
On 5/08/2022 at 6:00 AM, Black Panther said:

Papeete only has one high tide per day at noon.

Cool -it’s really  that far from everywhere else

Link to post
Share on other sites

Distance is not the issue. Think of Thor standing in one spot swinging his hammer, as the hammer crosses the ocean tides go up and down, more so the further you get from Thor. Bur where Thor is standing there is little or no movement.  Thor is standing in Papeete.

 

There are several Thors.

Link to post
Share on other sites

Maybe I have not read enough or watched enough Marvel to understand Thor :-) 

While I am certain it's perfectly valid, here's an alternative...

Think of it like carrying a shallow tray of water.  As you walk the water swishes from left to right up the sides, there is a middle, or fulcrum, point where the water hardly moves at all. Polynesia is located at the fulcrum point for the Pacific basin, (nothing to do with the equator), resulting in almost no tidal movement.

Tahiti, and Polynesia have no lunar tide.  The tide is about 20cm-30cm and is caused by the sun.

You'll get two high tides per 24hour day.

 

 

  • Like 1
  • Upvote 1
Link to post
Share on other sites

Didn't pick you as a flat earther CD? Like the analogy tho. Unless the carrier of the tray is drunk, then the tides out everywhere.

Does Thor swing perpendicular to earths surface or tangental? If vertical then Papeete is going to have massive tides, obvious dependent

on rpd, and if horizontal, hmmm, I guess his hammer must have a long handle and it might work.

Bizarre!

  • Haha 1
Link to post
Share on other sites

Try this

 

Near Tahiti though the lunar tide is cancelled because of an interesting phenomena called an amphidrome, or amphidromic point. As the lunar tidal swell passes around the earth and through the ocean basins, it gets broken up into lots of smaller swells, bouncing off continents and islands along the way, and it also gets affected by the Coriolis Force which bends it north and south. The ultimate effect is that there are places where a crest of the lunar swell meets a trough of the lunar swell, and cancels the tide out completely and these are the amphidromes. So with a lunar amphidrome located here we just have a solar tide, which is weaker, thus lower in amplitude, and locked into our normal 24 hour solar day. As you move away from Tahiti, into the Tuamotu Archipelago for instance or to the Marquesas, you get away from this amphidrome and the lunar tides begin to play a stronger role in the tidal cycle. 

  • Like 1
  • Upvote 1
Link to post
Share on other sites

The Mediteranian basically has no tide, any rise or fall is related to barometric pressure. It does have currents though, usually 6 hourly + - with very little time between the changes of direction, very noticeable in restricted waters. Between the mainland and the island of Evoia (Greece) for example or the straits of Sicily, (between Sicily and the toe of Italy being 2 of the more prominent ones). I believe the water comes into the Med from the Atlantic on the Spanish side and goes out on the African side and takes 7 years for 1 complete circulation, and then is also the water coming from the Black sea also adding to the flow.

Link to post
Share on other sites

Current enters the Med from the Atlantic through the Straights of Gibraltar at or near the surface right across but stronger on the northern side

Theres a counter current running out but down deep, it’s only 7nm wide but over 500m deep

When we came out there was 25kt W blowing and the current was 3 to 4kts

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...