Varying salt concentrations in the oceans

[BEM]

After having been underwater in warm sea water (Pacific and Caribbean), four times, I believe that there are different concentrations of salt for different areas. Regular sea water is 96.5% pure water and 3.5% salts, dissolved gasses, organic materials and undissolved particles.

Costa Rica – Pacific Coast = not very salty
Caribbean – San Andres Isla = bit salty
Caribbean - Cayman Brac / Little Cayman = not very salty
Honduras – Roatan = very salty.

Roatan (Jan 2004) water seemed to be very salty and burned my eyes for a longer period than any of the other three areas. Most of the other areas only were a minor nuisances and I got used to it. Other divers also agreed that it was extremely salty and the taste lingered for quite awhile. No rivers near any of our dive sites and rains were not a significant factor.

Also I needed two more pounds of weights than normal (should have used less as I've lost some weight and am in better shape.)

Anyone got any data or information on this.

 

[FredT]

Anyone got any data or information on this.

Sea salt concentration is done by both evaporation and freezing. Sea ice is nearly fresh water which leaves a very denseconcentrated brine at about 28°F. This cold salty water is what drives the Gulf Stream. High salt concentrations in warm water are found on the west side of the Bahama Banks, The Med, Red Sea, Persian Gulf, several other shallow temperate and tropical seas.

FT

 

[BEM]

Well I decided to revive this thread with some new information. ( I know the original poster personally - he sulks when his posts get buried!)


Colorado State University veteran hurricane researcher, W. Gray attributed the Caribbean warming to natural cycles. Gray said he believes salinity buildups and movements with ocean currents cause warming and cooling cycles.
He predicted the Caribbean water will continue to warm for another five to 10 years, then start cooling.

Some observations:

If water (ocean) levels are rising, then the salinity would decrease.

Makes sense that water with greater salinity levels would be able to receive and hold
more of the sun’s energy = higher temperatures.


Have you found, or even noticed, if saltier water is warmer?

 

[archman]

Any recent salinity changes will be small, and difficult to quantify except with sensitive instruments. The average diver will not be able to notice differences on the order of individual parts per thousand, which is what we're talking about.

It's not that saltier water is warmer, but that warmer water is saltier.

 

[Hank49]

I agree with Archman. If you needed more weight in the Caribbean, you probably had one too many enchilladas and packed on a few extra lbs of fat before diving here. The salinity range of any suitable diving area (meaning close proximity to a coral reef) in the tropics will be at least 32ppt. More likely 34-35.

 

[Charlie99]

I agree with Archman. If you needed more weight in the Caribbean, you probably had one too many enchilladas and packed on a few extra lbs of fat before diving here.

http://science.hq.nasa.gov/oceans/physical/SSS.html is an interesting article by NASA on sea surface salinity, including a few maps. Generally oceans are 32-37 practical salinity units, which for our purposes are equivalent to salt weight in parts per thousand. Obviously, areas near river mouths can be a lot lower. Some areas of the Red Sea are 42psu.

Temperature has a larger effect on density than does salinity changes. The chart below shows density vs temp on the left axis and salinity on the horizontal axis. The lines are density, where the "24" line corresponds to 1.024kg/cubic meter, 26 to 1.026, etc.

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One time in Cozumel I suspected that salinity was changing my required weighting. Salinity wasn't the problem. Nor was it Hank's extra enchilas. It was the handmade weights that were quite a ways off from the marked weights.

 

[drbill]

Makes sense that water with greater salinity levels would be able to receive and hold more of the sun’s energy = higher temperatures.

Hmmm... not to me. Am I missing something?

Archman got it right... warmer water can hold higher concentrations of salts than colder water (but lower concentrations of gasses).

 

[AXL72]

Adctually, try getting a salinity measurement at a lab. Not sure the conclusionsare are valid with "hurt my eyes more".

In fact, 28F (-2C) water can hold as much as a salinity of 40 (assuming ppt).

In the arctic, brine collects in hight concentration in the sea ice. The chart you posted is a neat generalized observations, but not always the rule.

By the way, a salinity test involves filtering the water sample, then running current through the water sample with two electrodes to measure conductance. Cheap test.


Actual data = 27.7 and 27.7 F with 33 to 37 ppt salinity
Actual data = several readinsg of 27.7 and 28 F with 29 to 40 ppt salinity

 

[Charlie99]

In the arctic, brine collects in hight concentration in the sea ice. The chart you posted is a neat generalized observations, but not always the rule.

Everything I've seen indicates that sea ice has a much lower salinity than the ocean. Newly formed sea ice has on the order of 1%/10ppt/10psu (about 1/3 of the salinity of the surrounding ocean). Older sea ice will decrease in salinity down to as low as 0.1%/1ppt/10psu to 0.3/3ppt/3psu range (1/10 to 1/30th of the salinity of the surrounding ocean).

 

[AXL72]

Sorry charlie.

I personally took the samples and the temperature readings of the water. Measurements were by another lab.

Albeit the samples were taken within 2 ft of the surface in slush in -20F air on one day and -10F air with 35 mph winds (-55 F windchill) on another.