Panama canal: why don't the two sides level out?

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Main Question or Discussion Point

The sea level is different from one side of the Panama canal to the other. The pacific side is 20 cm higher.

Why don't the levels equalize by water flowing around south america?
 

Answers and Replies

  • #2
Born2bwire
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Because of the locks. They only let enough water flow in/out to raise/lower the ship inside each lock. In such a way, they do not allow for a continuous flow of water between the two oceans but only small intervals of water.
 
  • #3
Cleonis
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The sea level is different from one side of the Panama canal to the other. The pacific side is 20 cm higher.

Why don't the levels equalize by water flowing around south america?
If there would not be any ocean currents at all then indeed it would not be possible for any level difference to exist, since by nature water forms a level surface.

I suppose that the 20 cm difference arises because of prevailing ocean currents. Presumably at each side of the Panama canal the ocean currents come out in such a way that difference in level arises.
 
  • #4
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Shouldn't the levels fluctuate seasonally if they were due to ocean currents?

By the way Born2bwire the locks are to carry ships over a mountainous area that is higher than both oceans, and also I asked why doesn't water go all around south america to equalize.
 
  • #5
Cleonis
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Shouldn't the levels fluctuate seasonally if they were due to ocean currents?
I think the major ocean currents are pretty consistent all throught the seasons.

The driving force is that around the equator the water is heated more than at higher latitudes. That differential heating tends to cause a circulation where surface water flows away from the equator, and deep water flowing back. The Earth's rotation tends to redirect that flow (coriolis effect), and geographic features also tend to redirect.

In all the ocean currents are determined more by geographic features than by seasonal features.
 
  • #6
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The Pacific Ocean is 20cm higher than the Atlantic. Not just through the canal.

This answers your question perfectly:

http://www.psmsl.org/train_and_info/faqs/#3
3. Is sea level of the Atlantic and Pacific oceans the same?
If so why are locks required in Panama?


Sea level is about 20 cm higher on the Pacific side than the Atlantic due to the water being less dense on average on the Pacific side and due to the prevailing weather and ocean conditions. Such sea level differences are common across many short sections of land dividing ocean basins.

The 20 cm difference business is determined by geodetic levelling from one side to the other. A datum called Panama Canal Datum is used. When you use spirit levelling you follow a 'level' surface (to our perceptions, see 1) which will be parallel to the geoid (which is geometrically a 'lumpy' surface). The geoid is the surface of constant gravitational potential (plus a 'centrifugal potential' term) which on average coincides with the sea surface i.e. a 'level' surface in everyday language. The 20 cm difference at Panama is not unique. There are similar 'jumps' elsewhere e.g. Skagerrak, Indonesian straits.

If the canal was open sea and not locks (i.e. if somehow a deep open cutting had been made rather than the canal system over the mountains) then there WOULD be a current flowing from Pacific to Atlantic. An analogy (although not a perfect one because there are many other factors) is that you could compare Panama to the Drake Passage off the south tip of Chile which has a west-east flow (but mostly wind-driven of course, but Pacific-Atlantic density must play some role).

Locks are needed in the Panama Canal because the canal climbs over the hills and makes use of mountain lakes. Therefore, locks would be needed even if sea level was the same on the two sides. (So, for example, there are also locks on canals here in England which is much less mountainous than Panama).

Note also that the tides have opposite phase on the 2 sides of Panama, so, if there was a sea level canal, there would be major tidal currents through it.
 
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  • #7
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So if we go to a long lake and disolve a lot of salt on one side of the lake, the opposite side will rise?
 
  • #8
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So if we go to a long lake and disolve a lot of salt on one side of the lake, the opposite side will rise?
If you dissolve a lot of salt the densities change so you'd expect some variation.

Also re-read what is in the link relating to gravity.
 
  • #9
Cleonis
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So if we go to a long lake and disolve a lot of salt on one side of the lake, the opposite side will rise?
Let me propose another setup.
Let there be two lakes, close to each other but not connected. Let the two lakes have the same level, and the same depth. Dissolve a lot of salt in one of the lakes, then establish a conduit between the bottoms of the two lakes (say, a water filled pipe.)

With that setup I expect that water will move through the conduit from the higher density lake to the lower density lake. The equilibrium point will be the point where the pressures at the two sides of the conduit are equalized.

So I think it's a case of communicating vessels, with a bias due to the density difference.
 
  • #10
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Shouldn't the two densities have equalized by now? It's been billions of years.
 
  • #11
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Shouldn't the two densities have equalized by now? It's been billions of years.
Only if there were no changes (no salt added or removed, weather and currents etc). But unfortunately, nature isn't that simple.
 
  • #12
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Maybe because there are more rivers flowing to the atlantic than to the pacific, per cubic foot of sea water?
 
  • #13
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Maybe because there are more rivers flowing to the atlantic than to the pacific, per cubic foot of sea water?
What?

Are you not reading what's been posted above?

I gave you the exact reasons why the Pacific is higher than the Atlantic. There's really no more to it.
 
  • #14
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You said changes prevent density equalization and therefore cause the difference in level. But changes happen on both sides. Currents too flow on both sides and seem completely unconnected. Are you yourself satisfied that currents cause one side to be heavier?
 
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  • #15
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What are you talking about? Stop making things up.

Please read my initial post in this thread. I quoted you an entire section of a site explaining exactly why the ocean levels are different.

I have never said the differing levels prevent density equalisation. Ever.

EDIT: Your edit noted.
 
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  • #16
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I have never said the differing levels prevent density equalisation. Ever.
Look at your #11 post:
- Shouldn't the two densities have equalized by now? It's been billions of years.
- Only if there were no changes.

What did you mean then, if not that changes lead to no equalization of density?
 
  • #17
2,685
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Look at your #11 post:
- Shouldn't the two densities have equalized by now? It's been billions of years.
- Only if there were no changes.

What did you mean then, if not that changes lead to no equalization of density?
RE. Bolded: That is exactly what I meant, but that isn't what you wrote.

The salt levels would only have equalised if there was no further input / removal of salt, among other things. This is not how nature works.

Again, I have never said the different levels prevents the salt level equalising.

There are changes in nature, salt is constantly added and removed alongside other factors that prevent the levels equalising.

Please read the link I provided, it explains it perfectly well.

I don't know if there's a language barrier here or not, but you aren't reading what I write correctly. As such, you are posting what amounts to non-sense based on what I've never said.
 
  • #18
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Good. You mean that changes lead to no equalization of density and you agree that no equalization of density leads to differing levels, correct?

In other words, A leads to B and B leads to C, does it not follow that A leads to C? In other words, that changes lead to differing levels? You do not say it word for word, but you say the equivalent.

The salt levels would only have equalised if there was no further input / removal of salt, among other things. This is not how nature works.
But since there is further input / removal of salt, one has to be denser, which is like saying

"if you input food to two childen, one will be fatter".

Well I suggested that one child seems to be fed more food. One ocean receives more salt. Where from? More rivers.

Please read the link I provided, it explains it perfectly well.
I have read it since the first time you gave it, and copy-pasted it. It does not account for a difference in density. It does not answer why SALT does not diffuse around south america to equalize densities.

You proposed that salt content does not equalize because, word for word, "only if there were no changes (no salt added or removed, weather and currents etc) [would the densities have equalized]. Well consider that salt is added to both sides, weather is similar on both sides, and only currents are perhaps one-sided in a salt-obstructing effect. But currents go in closed paths don't they? How can they obstruct diffusion?
 
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  • #19
2,685
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Well I suggested that one child seems to be fed more food. One ocean receives more salt. Where from? More rivers.
Rivers are fresh water, so how would the ocean get salt from them?

I have read it since the first time you gave it, and copy-pasted it. It does not account for a difference in density. It does not answer why SALT does not diffuse around south america to equalize densities.

You proposed that salt content does not equalize because, word for word, "only if there were no changes (no salt added or removed, weather and currents etc) [would the densities have equalized]. Well consider that salt is added to both sides, weather is similarly varying on both sides, and only currents are perhaps one-sided in their salt-obstructing effect. But currents go in closed paths don't they?
You enjoy closed systems don't you. I've read your other threads and it's a general theme.

Currents aren't "closed paths".

It is the continual processes occurring in both oceans, along with other factors (gravitational variation), that prevent them from equalising.
 
  • #20
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Currents aren't "closed paths".

It is the continual processes occurring in both oceans, along with other factors (gravitational variation), that prevent them from equalising.
Good, then that is a strong indicator that salts should distribute themselves worldwide, is it not?
 
  • #21
2,685
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Good, then that is a strong indicator that salts should distribute themselves worldwide, is it not?
They do distribute themselves. But because of the processes going on, it prevents them balancing out.

What the processes are I'm not entirely sure, but the fact they haven't balanced out tells you they are there and a bit of research will explain to you.

What exactly are you trying to get at by saying they haven't distributed themselves and not accepting there is a process(es) preventing it?
 
  • #22
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What exactly are you trying to get at by saying they haven't distributed themselves and not accepting there is a process(es) preventing it?
That there is a better explanation, that one ocean is fed with more salt. Mystery processes that conspire to produce observed result, or a simple explanation? Remember Occam's razor.
 
  • #23
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That there is a better explanation, that one ocean is fed with more salt. Mystery processes that conspire to produce observed result, or a simple explanation? Remember Occam's razor.
I've never said they are "mystery processes", only that I don't know what they are.

Scientists have the explanation, you just need to look.

Here is a page on the very subject:

http://eesc.columbia.edu/courses/ees/climate/lectures/saltyatlantic.html

It explains why the Atlantic is so salty.
 
  • #24
russ_watters
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Rivers are fresh water, so how would the ocean get salt from them?
Rivers contain more salt than the water that leaves the ocean via evaporation so the net effect is an increase in salinity.
 

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