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Author Topic: Salinity Depth and Seeding  (Read 1985 times)

jai mitchell

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Salinity Depth and Seeding
« on: June 16, 2014, 06:50:03 PM »
A response to the math challenge, how much salt would move how much water (at the Indonesian warm pool) how far into the ocean?


I wasn't asking you I was challenging you.  It is often the case that people will throw out ideas before looking at them because they don't fit with their preconceived notions.  In fact, this is what basically determines human understanding of everything from butterflies to politics (

the 1916 Helland-Hansen curve of Temperature Salinity;;doc.view=print shows the equilibrium temperature and Salinity profiles for the Gulf Stream between 20 and 180 meters of depth.

In a very clear correlation between this depth range the salinity drops (roughly) from 27.5C to 22C at 180 meters.  The corresponding Salinity for these depths are 36 0/00 (units are kg Salt/1000 kg of H20)  which increases to 36.6 0/00

Therefore, an increase of 6/10th of a kg of salt per 1000 kg of water is enough to equal a temperature differential of 5.5C

so lets increase the surface salinity of 1000 kg of water by adding 100 grams of salt, what is the associated change in temperature and where would the new equilibrium be found at depth?

answer:  (.916 k per tenth of 0/00 = 36 meters depth)

So if you injected 60,000 kg of salt into the 20m depth profile (where surface evaporation/wind mixing meets equilibrium) then you would move 600,000 cubic meters down an additional 18 meters (accounting for temperature differentials = -50% penalty).

If even a thin slice of water 1 cm was spread out and moved at this volume it would still only be 680 X 680 meters.   However, the contribution of this effect to the already strong evaporation/vertical mixing in the region would certainly push the equilibrium mixing layer (now at 20 meters depth down an additional several meters.

At this point though one must realize that we are talking about  hygroscopic cloud seeding, a process where salt water is sprayed over cumulus clouds to generate a "hot rain"  this rain is coming down at temperatures that are significantly warmer (approximately 7-10C warmer) than the ocean surface temperature, causing a regional warming and salinity increase.  This process will increase the rate of heat deposition into the lower layers (via wind mixing) by an amount that is significantly greater than the increased mixing caused by the introduction of salt. 

While the amount of down welling caused by salting is small (in relative volume to the incident mass) the amount is significant if considered with the rates of surface mixing normally found in this region due to evaporation and wind.  (effectively pushing the mixing layer to a new depth profile)

So, the answer is:

Yes the amount of down welling is (relatively) small.

It looks like the increase in surface temperature, mixing rates and the expansion of the subsurface mixed layer depth profiles will have a much larger effect (of heat deposition)

unfortunately, I cannot quantify the actual additional heat deposition values since I do not know the current regional surface mixing rates from 0-20 meters of depth.

However, the amount is not negligible.  This region has observed an increase in heat=depth profiles recently that are extremely unusual.

« Last Edit: June 16, 2014, 08:11:42 PM by jai mitchell »
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