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Ocean Currents


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#1 OceanBreeze

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Posted 10 January 2017 - 11:50 AM

I could have sworn I saw a thread here about ocean currents and made a mental note to myself to post a reply. I must have imagined it!

 

 

Ocean currents are very complex, involving the tides, winds, thermohaline circulation and all of these are variable, including seasonal changes but I am not familiar with any “centrifugal force” theory of ocean currents, that I imagined I saw. :lol: 

 

 Anyway, if anyone is interested this is an excellent source of information.

 

perpetualocean_cover.jpg

 

 



#2 DrKrettin

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Posted 10 January 2017 - 12:09 PM

Awesome. Somebody recently mentioned that Coriolis forces were significant.



#3 exchemist

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Posted 10 January 2017 - 12:31 PM

Awesome. Somebody recently mentioned that Coriolis forces were significant.

I mentioned that I thought they would be, on the basis that they are for winds.

 

This Russian post and poster seem to have vanished. Perhaps it was a drive-by by the FSB. :) 



#4 OceanBreeze

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Posted 11 January 2017 - 02:13 AM

Awesome. Somebody recently mentioned that Coriolis forces were significant.

 

 

The incoming energy from the sun is what powers the winds, and the rotation of the earth, acting via the Coriolis force, sets up the general circulation pattern of wind flow. In the Northern Hemisphere, warm air rising at the equator and flowing northward is turned to the Right (Eastward) by the Coriolis force. At about 30° latitude this warm moist air comes down and returns to the equator in an Westerly stream known as the Trade Winds.

 

walker_circulation.jpg

 

The winds drag on the water’s surface via friction, this causes water currents to move in the same general direction as the wind blows. These major gyres of ocean-circling currents occur both North and South of the equator. So, it is correct to say the Coriolis effect results in the general direction of circulating water currents, just as it does for the wind.

 

winds2.jpg

 

The Coriolis doesn’t have any effect on wind velocity; that is determined mainly by differences in barometric pressure, which also has a large effect on water levels. Hence, water level and water currents are significantly affected by both barometric pressure and the direction and duration of the winds.

 

I don’t know what point the original poster was trying to make, as I only had the opportunity to briefly skim through his rather long post. If I recall correctly, he felt that centrifugal force was a major determining factor in seasonal water levels, and then he posted a lot of data pertaining mainly to coastlines, not ocean currents. It seems to me he was conflating tides with ocean currents. It is well established that coastlines do undergo seasonal cycles in their tides due to several obvious facts; the difference between summer and winter water and air temperatures, the amount of precipitation and runoff, and seasonal changes in wind speed and direction.

Because of many variables and complexity, not everything is known about tides and ocean currents, but I see nothing to be gained from a dubious claim about centrifugal forces.

 


Edited by OceanBreeze, 11 January 2017 - 05:41 AM.


#5 exchemist

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Posted 11 January 2017 - 02:46 AM

The incoming energy from the sun is what powers the winds, and the rotation of the earth, acting via the Coriolis force, sets up the general circulation pattern of wind flow. In the Northern Hemisphere, warm air rising at the equator and flowing northward is turned to the Right (Westward) by the Coriolis force. At about 30° latitude this warm moist air comes down and returns to the equator in an Easterly stream known as the Trade Winds.

 

walker_circulation.jpg

 

The winds drag on the water’s surface via friction, this causes water currents to move in the same general direction as the wind blows. These major gyres of ocean-circling currents occur both North and South of the equator. So, it is correct to say the Coriolis effect results in the general direction of circulating water currents, just as it does for the wind.

 

winds2.jpg

 

The Coriolis doesn’t have any effect on wind velocity; that is determined mainly by differences in barometric pressure, which also has a large effect on water levels. Hence, water level and water currents are significantly affected by both barometric pressure and the direction and duration of the winds.

 

I don’t know what point the original poster was trying to make, as I only had the opportunity to briefly skim through his rather long post. If I recall correctly, he felt that centrifugal force was a major determining factor in seasonal water levels, and then he posted a lot of data pertaining mainly to coastlines, not ocean currents. It seems to me he was conflating tides with ocean currents. It is well established that coastlines do undergo seasonal cycles in their tides due to several obvious facts; the difference between summer and winter water and air temperatures, the amount of precipitation and runoff, and seasonal changes in wind speed and direction.

Because of many variables and complexity, not everything is known about tides and ocean currents, but I see nothing to be gained from a dubious claim about centrifugal forces.

 

Fair enough, but I was thinking Coriolis forces would be expected to have a direct effect on the direction of circulation of water currents as well. Any body of water in the N hemisphere moving South towards the Equator or North away from it would be deflected such as to set up a clockwise circulation, wouldn't it? Or is the motion of water currents considered to be too slow for this to have any impact?



#6 OceanBreeze

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Posted 11 January 2017 - 05:45 AM

Fair enough, but I was thinking Coriolis forces would be expected to have a direct effect on the direction of circulation of water currents as well. Any body of water in the N hemisphere moving South towards the Equator or North away from it would be deflected such as to set up a clockwise circulation, wouldn't it? Or is the motion of water currents considered to be too slow for this to have any impact?

 

Yes, there would be a direct effect if the body of water was flowing North-South to begin with. But the largest effect is from the winds which do blow North-South due to atmospheric conditions.