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View Full Version : Could ocean/sea surfaces be cooled by circulating water from depth ?


am77494
09-19-2017, 05:54 PM
Is there any existing research on the subject ? New York's aqueducts move about 1.2 billion gallons of water per day.

Would a circulation rate close to the above make any dent to the surface temperature ?

What about speeding up conduction something like a heat pump but in reverse ?

Ludovic
09-19-2017, 06:22 PM
The Gulf Stream moves at least 30 million cubic meters per second according to Wikipedia which is several orders of magnitude higher. It affects around the same area that we would need to change in order to affect hurricane formation (which I know you weren't asking about but assuming you are.) On the other hand, the temperature difference it induces is more than sufficient to affect the climate.

So, unless I"m not being conservative enough, you'd need the equivalent of many New York aqueducts, and power them, to make a temperature difference in a semi-regional area. And I might be underestimating the number: it might be completely undoable.

TriPolar
09-19-2017, 06:59 PM
Water moves through New York's aqueducts by gravity. You'll produce a lot of heat trying to pump enough water from the depths upward with conventional means. Maybe you can make some huge heat engine that uses the difference in temperature between the surface water and the depths to run the pumps. Not so sure heating the water at depth is going to be a good idea at all. The warmer water will rise, currents may carry it somewhere else, and it could have a lot of ecological impact, possibly adding to the problem.

watchwolf49
09-19-2017, 07:02 PM
The New York aqueducts are (in part) gravity fed, so basically free ... pumping cold water up to the sea surface would require a pump and the energy draw thereof ... it would cool the surface, but this is a convective heat transfer mechanism, same with heat pumps ... there's really nothing that causes conduction to increase, except larger temperature differences ...

However, all it not lost ... it's possible to passively drive warm surface water down to depth ... "Another Look at an Unorthodox Hurricane-Prevention Idea" (http://freakonomics.com/2012/11/06/another-look-at-an-unorthodox-hurricane-prevention-idea/) ... I see no reason this won't work in a localized area ...

Senegoid
09-20-2017, 03:17 AM
Is there any existing research on the subject ? New York's aqueducts move about 1.2 billion gallons of water per day.

Would a circulation rate close to the above make any dent to the surface temperature ?

What about speeding up conduction something like a heat pump but in reverse ?

If you're talking about doing this to solve Global Warming, keep the sea from rising, and reduce hurricanes -- probably too big a task to make a dent in, as everyone in this thread seems to be saying.

However, aside from that, there IS a process called Ocean Thermal Energy Conversion (OTEC) that uses this very idea as a renewable energy source. The idea is to find areas of the ocean where there is a greater-than-average temperature gradient between the surface and deeper waters, and use that gradient to generate electricity. This typically works best in warmer tropical waters, like around Hawaii and in the Caribbean.

Wherever you have a temperature gradient, heat energy will flow from the hot area to the cooler area. That is basic thermodynamics. It's possible to capture and manipulate that energy flow to perform work, like driving a turbine. Several technologies have been studied, but I think the one that's gotten the most traction is the simple heat exchanger.

Cold water is pumped up from the depths, while warmer water is taken from the surface. These are brought into close contact through a heat exchanger apparatus (essentially the "heat pump" that OP suggests, similar to the workings of a refrigerator), and the energy flow can be captured to drive a generator.

Here are a few examples of pages I just found on-line that discuss the process. There are many others:

http://www.explainthatstuff.com/how-otec-works.html
http://www.otecnews.org/what-is-otec/
https://www.makai.com/ocean-thermal-energy-conversion/

I first heard and read about this in an Introductory Oceanography class I took in Hawaii, circa 1984, when the research was mainly in its infancy.

bob++
09-20-2017, 03:26 AM
I would also be concerned about pumping stuff up from the bottom that should really stay there. The Suez Canal is causing problems in the Med, because there is a flow of water etc from the Red Sea. It is relatively small but has been going on for a long time. Who knows what damage some deep sea biology might do on the surca and warmed up?

naita
09-20-2017, 07:52 AM
Who knows what damage some deep sea biology might do on the surca and warmed up?
Deep sea biology stays in the deep because it can't live elsewhere. Not because it's unable to get to the surface.

watchwolf49
09-20-2017, 07:57 AM
Another problem is keeping the cold water at the surface ... it's more dense so it will just sink ...

LSLGuy
09-20-2017, 08:16 AM
Deep sea biology stays in the deep because it can't live elsewhere. Not because it's unable to get to the surface.True. But if we're altering the temperatures at the surface then we're also altering the temperatures in the deep.

Which might not make the current deep sea critters happy.

Exapno Mapcase
09-20-2017, 10:04 AM
Is there any existing research on the subject ? New York's aqueducts move about 1.2 billion gallons of water per day.
One estimate of the Atlantic ocean is 82001247453000000000 gallons.

That's always the problems with geoengineering. It's nearly impossible to grasp how freaking huge the Earth is.

watchwolf49
09-20-2017, 10:38 AM
True. But if we're altering the temperatures at the surface then we're also altering the temperatures in the deep.

Which might not make the current deep sea critters happy.

Pressure is the problem, it's easy to keep water at 4șC, but the critters just simply explode on their way up ... any water not at 4șC will be buoyant in 4șC water ... but that's at the bottom of the oceans ... we only need to go down a few hundred's of meters to find water cold enough ...

Bones Daley
09-21-2017, 01:56 PM
Pressure is the problem, it's easy to keep water at 4șC, but the critters just simply explode on their way up ...

Has the explosion thing been verified? I have no cite, but I do seem to have a recollection of seeing pictures of some creature which had been removed from the deep ocean bed, and was still intact at sea level.

I would surmise that the internal and external pressure would just equalize as the creature rose to the surface ... it would probably experience whatever the piscine equivalent of the "bends" might be, and it almost certainly would not enjoy the experience overmuch, but I would be surprised if any "explosion " were to occur.

eburacum45
09-21-2017, 02:24 PM
If we could make OTEC technology work efficiently enough, there is enough of a thermal gradient in the Gulf of Mexico alone to power the world. So the motivation is there.

Weisshund
09-21-2017, 02:32 PM
Somehow i do not think mankind is able to generate enough energy efficiently enough for long enough to go recirculating enough ocean to make any kind of change.

The ocean is a very very very large thing, and it already has its own ideas about circulation and heat distribution

naita
09-21-2017, 02:57 PM
Has the explosion thing been verified? I have no cite, but I do seem to have a recollection of seeing pictures of some creature which had been removed from the deep ocean bed, and was still intact at sea level.

I would surmise that the internal and external pressure would just equalize as the creature rose to the surface ... it would probably experience whatever the piscine equivalent of the "bends" might be, and it almost certainly would not enjoy the experience overmuch, but I would be surprised if any "explosion " were to occur.

It does happen to some extent to beings with internal pockets of gas, such as fish with a swim bladder. The gas expands and can push internal organs and the eyes out of the body: https://themarinedetective.com/2012/07/22/rockfish-barotrauma/

Creatures consisting almost entirely of non-compressible material, not so much.

PatrickLondon
09-21-2017, 03:20 PM
Don't you dare muck about with the Gulf Stream. Every now and again someone scares us all by talking about climate change reversing the Atlantic Conveyor, and us ending up with a climate more like everyone else on the same latitude.

boffking
09-21-2017, 03:22 PM
This is exactly what hurricanes do. They churn the water and bring up cold water from below.

wolfpup
09-21-2017, 06:40 PM
Keep in mind that the deep oceans are warming, too (https://www.scientificamerican.com/article/deep-ocean-waters-are-trapping-vast-stores-of-heat/), just not as fast as the upper layer above 700 m, because all kinds of factors produce vertical mixing. It's one of the reasons that El Nino and La Nina have net effects on global average temperature and not just regional effects that cancel out.

watchwolf49
09-21-2017, 06:43 PM
It does happen to some extent to beings with internal pockets of gas, such as fish with a swim bladder. The gas expands and can push internal organs and the eyes out of the body: https://themarinedetective.com/2012/07/22/rockfish-barotrauma/

Creatures consisting almost entirely of non-compressible material, not so much.

Apparently, it's the fatty lipids that ooze through the cell membrane ... so the cell wouldn't "explode" like dynamite or anything ... but it's enough to kill some critters on their way up the water column ... those critters that would survive do survive and thus are available at the surface anyway ... or some such ...

We will find cold enough water down a thousand foot, so the main environmental disaster will probably be the cooling effect on the surface ...

Ludovic
09-21-2017, 07:04 PM
Don't you dare muck about with the Gulf Stream. Every now and again someone scares us all by talking about climate change reversing the Atlantic Conveyor, and us ending up with a climate more like everyone else on the same latitude.That's pretty flippin' scary. But like I said it's a couple orders of magnitude from feasible before you could muck with it. But if you could it would affect a billion or so people.

LSLGuy
09-21-2017, 08:25 PM
Pressure is the problem, it's easy to keep water at 4șC, but the critters just simply explode on their way up ... any water not at 4șC will be buoyant in 4șC water ... but that's at the bottom of the oceans ... we only need to go down a few hundred's of meters to find water cold enough ...Sounds like you're worried about transporting the creatures up the water column. "By-catch" of the human-driven circulation if you will.

I was thinking of the opposite problem. The creatures stay in the deep. But as we "mine" the deep cold water by drawing it up, there's a net motion of thermal energy down. Despite the fact warmer water floats on colder.

The end effect is we pollute their deep cold environment by making it an equally deep but warmer environment. Which may upset their delicate sensibilities and ecosystems.

The deep ocean is a lot like a desert. It's biologically inhospitable and anything surviving there is barely getting by in some carefully honed narrow niche. Whacking a deep ocean or a desert has a lot more opportunity to create mass die-offs than does whacking a thriving temperate forest.

watchwolf49
09-22-2017, 08:58 AM
[whimper] ... it's only a thousand feet ... what could possibly go wrong? ...

Isilder
09-22-2017, 08:57 PM
Another problem is keeping the cold water at the surface ... it's more dense so it will just sink ...



Thats why you'd pump the hot water down and mix it with the water in the depths ?


BUT, reducing the temperature of the waters surface reducing the cooling of the earth.. because warmer water loses heat faster, that would be to space on a clear night , it can be backward to desired effect.. Cooling the surface can increase the average temperature of the ocean .. thus making the treatment backfire ??


Basically warm ocean surfaces is a symptom of global warming. There's no treatment of that symptom.

The only cure is curing global warming.

race_to_the_bottom
09-26-2017, 07:43 PM
One estimate of the Atlantic ocean is 82001247453000000000 gallons.

Far too many significant figures (https://en.wikipedia.org/wiki/Significant_figures).

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