Re: Need Beginner Equipment Help

John Hanson wrote:
"-hh" wrote:
By any chance, are these are the same guys that said that a thermocline
of 35F water could exist below a 40F layer? :-)

It's true. I've witnessed it as has just about every other diver up
here as well. You don't account for underground streams and run off.

Thermoclines are density-based and can be overcome by flow.

Come up next June and I'll introduce you to
those cold waters below the surface.

Or you could head east in March/April and do a dip in Dutch. Dutch
traditionally has thermoclines so strong that even novices with poor
buoyancy control can lay on them.



Here's a good illustration of how lake waters typically respond. Sorry
I wasn't able to find one specifically for Lake Superior, but that's
your assignment:

....


Lake Superior is really an inland sea.

Even oceans can't ignore the laws of water density.


You are treating Superior as if it was some little lake like you have
down there in Texas.

A) I'm not in Texas.

B) The physical properties of water do not regionally vary.

C) Lake Superior is tiny in comparison to the Atlantic Ocean.


What you fail to realize is that warmer water is
constantly running off into it after about May and continues until
winter sets in.

So you have hot and cold running streams, depending on what temperature
you want the lake to be? How convenient!


We don't get a lot of rain in November and when we do
get precipitation, it is usually snow and it doesn't readily run off
at that time of year. If it did, you'd see run off temps at
around33-35 degrees.

Look at it this way:

Lake Superior contains 2934 cubic miles of water, which is roughly 4.3
E+14 cubic feet.
For easier math, let's round down the volume by ~10% to an even 4E14.

The combined inflow to *ALL* of the Great Lakes has to equal its
outflow. Otherwise, the lakes would either empty, or continuously get
deeper.

Looking at just Lake Superior, its inflow gets dispersed as outflow
into the next Lake and evaporation. In turn, the next lake down the
chain has its own watershed and outflows. Eventually, it all goes over
Niagra Falls.

The combined flow of Niagra Falls is 6 million cubic feet/minute
(Wiki).

6E6 ft^3/min * 60 = /hour * 24 = /day *365 = /year = 3.15 E+12 cubic
feet per year
For easier math, let's round up the outflow by 25%, to an even 4E12


Dividing Lake Superior's volume by Niagrar's outflow:

4E14 / 4E12 = 1E2 = 100

In other words, if one tried to empty Lake Superior with just the flow
that goes over Niagra, it would take 100 years. However, what this
also suggests is that the annual influx into Lake Superior is only
roughly 1% of its volume.

Assuming that Lake Superior was at an average temperature of 5C (41F)
and its heat influx flow was equal to the flow of Niagra Falls ... but
literally at boiling (100C = 212F), with no other system changes, how
long would you need this amount of heat input to raise the average
temperature of the lake by 1 degrees C?

Answer: roughly 1 year.

However, since we don't have a Niagra of boiling water, what this
really means is that the temperature variation of water influx might
cause some highly localized effects, but its effect on the system as a
whole - - to use the proper scientific term - - is "diddly squat".



And "coldest" means "lake ice will be the thickest".

No, the water under the ice is always at a constant temperature of
around 40 degrees. You'd know that if you ever did and ice dive.

So "up north", water freezes at 39F? :-)


Start your planning now for doing a Halloween dive in a Farmer John.
According to your buddies, the lake's water temperature should be just
past peak ;-)


The last day of October is considerable different than the first day.

So you're now claiming that the lake goes from its hottest to 'dang
chilly' in only 4 weeks?



But, some folks dive Superior every month of the year. Check this guy
out.
http://www.superiordivers.com/Images/Brads%20pics%20046.jpg


Hmmm..."3 out of 4 Lake Superior Divers are stupid enough to put their
masks on their foreheads". Oh, and the guy without a drysuit is the
only one not smiling.


-hh

.

Relevant Pages

  • Re: Need Beginner Equipment Help
    ... Even oceans can't ignore the laws of water density. ... Lake Superior is tiny in comparison to the Atlantic Ocean. ... So you have hot and cold running streams, depending on what temperature ...
    (rec.scuba)
  • Re: Swimming in cold water, part 2
    ... The 5C lake would be Lake Superior. ... surface water moves away and the cooler ... I have heard that the temperature cycle in Lake Superior is two month ... only the surface water gets warm and weather ...
    (rec.sport.swimming)
  • Re: Need Beginner Equipment Help
    ... traditionally has thermoclines so strong that even novices with poor ... You really should dive Superior. ... They certainly do within the same body of water. ... asked you for Climatological data for Lake Superior. ...
    (rec.scuba)
  • Re: Lake Superior dropping and warming, fishing and boating effected
    ... Filed Under: Nation News, Science News ... gray, choppy Lake Superior, Michigan Tech University chemist Noel ... a water sample from the bottom. ... Wal-Mart and Halliburton teamed up to ship another ...
    (rec.boats)
  • Re: Lake Superior losing water
    ... The mystery of Lake Superior's low levels, ... The shoreline of Lake Superior at Pukaskwa National Park ... fresh surface water. ... Its average temperature has surged about 4.5 degrees Farenheit since ...
    (rec.outdoors.fishing)