1. Originally Posted by archman
Freshwater is densest at 4C. Saltwater is not.
at the average salinity of the ocean, it is right around 4C (plug and chug into inverted mile's calculator and you can find out exactly where).

Deep-sea temperatures vary quite a bit, around six degrees or so. Sometime it's above 4C, more often it's below it.
i'm typically referring to water below the thermocline, which is always below 4C... it slowly keeps dropping. however, the depth at which the thermocline occurs varies for certain.

without a true model of all the ocean, i.e. sea floor depth, salinity, etc., all you can really do is approximate based on averages. i.e. we know about 70% of the oceans' water is below the thermocline, which means <4C. we can also pick some average value for salinity. otherwise, massive finite element analyses would be required to figure out what really would happen.

the point then, is to show averages and run the numbers from there. everybody has to do the same thing simply due to the sheer complexity of the problem.

taks

2. Originally Posted by Fram
Wouldn't this result in even more and stronger hurricanes, making this years naming until Delta (or has there been an Eta as well?) seem like a mild year? Just a thought...
Living in Houston, that thought has occurred to me more than once. BTW, we did get past Delta. Epsilon was next, though, and will be followed by Zeta then Eta (if either storm forms, it will likely not bother anyone other than sea captains and dolphins).

3. Originally Posted by Taks
at the average salinity of the ocean, it is right around 4C (plug and chug into inverted mile's calculator and you can find out exactly where).
Well, if it were that simple, I wouldn't have been laughed down 5 years ago. "Average salinity" in the ocean varies by reference cited, and so does "average temperature". I've got one text in front of me that states "the mean temperature of the ocean" at 3.5C; that's deep AND shallow water mind you. Two online sources state two values different than this, only one of which is >4C (and that's equatorial water). A more basic text I've got merely states that "the bulk of all ocean water is colder than 4C". My favorite text (Gage and Tyler, 1992) states that "temperature of the waters of the deep sea varies from 4C to -1C".

Thus, 4C is more of the high end value. Excepting the Red Sea and Med, which are pretty dang hot.

i'm typically referring to water below the thermocline, which is always below 4C... it slowly keeps dropping. however, the depth at which the thermocline occurs varies for certain.
The so-called "4C isotherm" is generally poo-pooed nowadays for its lack of accuracy, and "permanent thermocline" or "pycnocline" are much more favored. And it's only expected in temperate and tropical seas. Water below these layers can be over 4C certainly... it is in the Gulf of Mexico where I work, for example. An Aussie source states the LOW end of the perm. thermocline at 8C. I don't know if the Red Sea has a permanent thermocline, but as water 2,000+ meters down can often be >20C, either it's got one hot pycnocline or there ain't one at all.

Thus I no longer refer to the "4C isotherm" in public, else some oceanographer heckle me to death. They follow me around like cockroaches!

If the global climate modelers are using 4C to "simplify" things, they're going to have a great deal of explaining to do. From my authorites, I would guesstimate a better average value of between 3.5C and 3.8C.

Hmm... it now occurs to me that maybe folks are rounding up their model values to 4C for press release and introductory text use. That would make sense, although given the monstrous differences between tenths of a degree of global water temps, this smacks of silliness.

4. Originally Posted by archman
Well, if it were that simple, I wouldn't have been laughed down 5 years ago. "Average salinity" in the ocean varies by reference cited, and so does "average temperature".
i never said it was... i clearly stated that it would be very difficult to model completely. the point of using average values, however, allows a general idea of how the overall ocean will expand and contract. one must keep in mind, however, that using such generalities will typically increase the error bars around the result. my point, however, is that the original "sea is rising" calculations were based on an assumption that all water will expand when warmed by a few degrees. this point is patently false, since most of the water in the oceans will, in fact, shrink if/when warmed.

Thus, 4C is more of the high end value. Excepting the Red Sea and Med, which are pretty dang hot.
i realize this, and did note that 4C is about the high end below the thermocline.

The so-called "4C isotherm" is generally poo-pooed nowadays for its lack of accuracy, and "permanent thermocline" or "pycnocline" are much more favored.
i used thermocline. in general, it is about 4C though it does vary.

Thus I no longer refer to the "4C isotherm" in public, else some oceanographer heckle me to death. They follow me around like cockroaches!
hopefully not carrying raid or anything.

If the global climate modelers are using 4C to "simplify" things, they're going to have a great deal of explaining to do. From my authorites, I would guesstimate a better average value of between 3.5C and 3.8C.
no, actually, they aren't even using that. they (originally) assumed the water was much warmer and would ALL warm the same. they assumed a decrease in density based on an initial temperature much warmer than at the thermocline.

Hmm... it now occurs to me that maybe folks are rounding up their model values to 4C for press release and introductory text use. That would make sense, although given the monstrous differences between tenths of a degree of global water temps, this smacks of silliness.
more than just rounding, they're assuming surface temperatures.

the original expanding sea comments i've seen were all rather tounge-in-cheek so to speak. really, people just assumed a few degrees C meant some percentage decrease in density and a corresponding increase in volume and oila! we're all under water. i merely attempted to show a general analysis as to why that assumption is incorrect. while i could not give exact numbers, i did manage to show why the expansion theory is flawed... at least to the point that using such numbers is questionable (at best). what would really happen is too complex to model with simple pen and paper if one desires accuracy.

taks

5. Originally Posted by Lord Jubjub
Living in Houston, that thought has occurred to me more than once. BTW, we did get past Delta. Epsilon was next, though, and will be followed by Zeta then Eta (if either storm forms, it will likely not bother anyone other than sea captains and dolphins).
btw, when considering atlantic storms as an "indicator", one must also consider pacific storms. it should be noted that "global" anything will, by definition, impact the entire globe in one way or another. that said, the atlantic is warm indeed, resulting in a bunch more storms than normal, but the pacific, alas, is cool this year... the result? fewer storms. i do believe the "normal" number of storms for the globe is 90 +/- 10 or so... and this year is no exception.

global warming, btw, actually predicts more el ninos, which are devastating for atlantic storms (the westerly winds tear them apart apparently).

taks

6. Originally Posted by Taks
i used thermocline. in general, it is about 4C though it does vary.
No Taks, stay away from the evil thermocline word! "Thermocline" can refer to ANY boundary layer with measurable temperature differences above/below. Water masses routinely have several of these, at least. Eek!

7. Originally Posted by archman
No Taks, stay away from the evil thermocline word! "Thermocline" can refer to ANY boundary layer with measurable temperature differences above/below. Water masses routinely have several of these, at least. Eek!
??? even you used the phrase "permanent thermocline" or "pycnocline"...

i believe that's what i was referring to. i'm not sure of the semantic difference now.

taks

8. Originally Posted by Taks
btw, 2 x 3.7 cm is 7.4 cm or 3 inches, not 6.
My bad. I'd toss out my calculator and get a new one but I've been informed that the beads are made of lead and I don't have a permit for the proper disposal.

9. LOL!

i can't complain... i do most stuff in my head and it's nearly as reliable as your beads. i'm still wondering about the paint i used to play with as a child, too...

taks

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