Two questions for 100ft Lakes diving!

[MasterGoa]

As backround, this will be done on wrecks.
Maby deeper, but I will aim for 50-100ft.

So here goes:

1- Does a thermocline work backwards when surface
temps is near freezing?

Lets say you have 45F water at 100ft in Lake Huron in summer.
Will the water at this dept stay at 45F when surface temp goes lower?

2- It has been suggested, in another thread, to eat well before diving cold
to keep resources available for heat production.

Any suggestions on what is easy to digest and provided ample
energy for a 1 hour dive? (1 hour being that the food must not
digest instantly like sugar and stuff...)

So here you go

Thanks in advance for the answers.

MG

 

[MasterGoa]

Shameless bump!

Wow, no one has opinions on this?

Hmmmm.....

 

[Dean810]

This is a quote from the book, "The Certified Diver's Handbook" by Clay Coleman:
" An interesting phenonomenon occurs if the surface temperature of a lake or quarry approaches the freezing point in winter. As water molecules approach the freezing point, they organize themselves in a way that reduces density (that's why ice floats). When this occures, the freezing or near freezing water near the surface is less dense than the warmer water beneath, and a reverse thermocline develops. The cold water is on top and warmer water is beneath." So you seem to be right, although I haven't actually dived in the winter proper yet, so haven't experienced it. This of course reverses itself in the Spring.

I'm sorry, but I don't know anything about the proper food to eat!

 

[diverbrian]

All that I know is that the couple of times that I have been under ice, it has been one heck of lot warmer in the water than in the air. But that makes sense as the coldest that the water beneath the ice can go down to is the freezing temperature for that pressure. Wind chill may be somewhere below zero F . (Yes, I have been crazy enough to dive in those conditions.)

As for food, all that I can recommend from the cold water diving that I do is to stay away from "heavy" types of foods and acidic foods. I have had a real bad experience on deco with orange juice wanting to tear my stomach up. Thank goodness it was at Gilboa because I surfaced so wiped out that I don't know how I would have made up a boat ladder in pitching seas.

 

[MasterGoa]

Duly noted!

My instructor recommends plain whole wheat pasta 1 hour before
a dive...

Instructors at my school also say that the second thermocline never changes
temperature during the year.

So if you have a thermo at 30ft and one at 100ft, the 100ft one stays put...
At around 42F

 

[Dive1Dennis]

In my experience (mostly lake MI), the thermocline is sharpest in the summer when the surface water is warmer. Late season and especially in the spring the thermocline will be gone. The bad news is that there is no thermocline because it is cold from top to bottom! Around 100' or so the temperature drops a few degrees in the winter, but so does the surface temp. In April when we get out for the first time it is usually around 38F. top to bottom. I won't say it does not happen, but I have not experienced a reverse thermocline.

 

[cmufieldhockey8]

The more dense a food is, the longer it takes to digest. High fiber stuff like apples and carrots will be more likely to "sit" in your stomach, whereas something more with the consistancy of a smoothie won't do that. Not like you'd eat a cold smoothie before going on a cold dive but I'm sure you get the picture. Pasta sounds good.

Eating a LOT of protein (like beef jerky) or a LOT of sugar (candy bars) is obviously more likely to upset the stomach too. I've done a lot of sports nutrition lectures and tell athletes that whatever they do, make sure they eat something they are used to eating and something they know they wouldn't be burping up later. You'd never catch me eating peanut butter or oranage juice before a dive for that reason. I've got a minor in nutrition but I definitely not a registered dietician so take anything I say with a grain of salt.

 

[do it easy]

I like to carbo load the night before the dive- 12 ounces at a time...

Because of the van Der Waals forces that Dean alluded to, water is maximally dense at 4C, give or take. So the surface can be frozen, while the water beneath remains above freezing. There is also some mechanism where lakes "turn over" where the bottom layer moves up and the top layer moves down.

In short, I suppose a "reverse thermocline" is possible since the bottom is usually 35f-48f, while the top goes from 32f-80f.

 

[theskull]

A couple food suggestions for before or between winter dives:
Oatmeal
Chicken noodle soup
Bananas
Protein bars
(NOT all at once!)

theskull

 

[Rick Inman]

I have noticed the reverse thermalcline in my area when ice starts developing around the bays. But really, at 34f near the surface and 37f at depth, who cares? Personally, I can't tell the difference.