Cold water diving

[Tomeck]

Those are some cool(!) pics Tomeck! What kind of fish is it I see in one??!

Here are some from me: Ice, Ice, Baby!


Takes a while to load I suppose...

Good movie!

This is a trout.

 

[Lauri]

A couple of weeks ago water temperature was -1 celsius and it wasn't that cold. Dive time was 40 minutes but you could have been even longer.

 

[KOMPRESSOR]

A couple of weeks ago water temperature was -1 celsius and it wasn't that cold. Dive time was 40 minutes but you could have been even longer.

Where was this? I cannot have been in Finland, because the salt level in the Baltic Sea is to low to affect the freezing point that much. I bet you have a Suunto computer!

There are Suunto temps, and there are real temps...

 

[dave4868]

Went diving this week in Montana and our computers both said the water temperature was 30 degrees at about 60 feet. I understand that increased pressure will lower the freezing point but didn't think it would be that much at that depth. Just wondering what the coldest water temps anyone has experienced in fresh water?

It's time for calibration, I think. Get a bucket of ice water and several thermometers you think are accurate.

Not really surprising that the Suuntos would read the same. I'd be interested in hearing how far they are off.

I'll bet flowing freshwater can get close to 32F though. We need to hear from the prospecting river divers in Alaska....

Coldest freshwater I've seen has been 34F both under ice and in open water. Also saw as high as 37F under ice.

Dave C

 

[Jafo123]

Why? I live up here and don't find the idea of freezzing my but off any fun at all. Although I have thought about giving it a try some day. I THINK I'M GOING CRAZY SAYING SOMETHING LIKE THAT!

 

[KOMPRESSOR]

I'll bet flowing freshwater can get close to 32F though. We need to hear from the prospecting river divers in Alaska....

Are you kidding??! Do you need to hear it from someone else that freshwater freeze up at 32F? It does... Put some salt in it and it'll keep kind off "flowing" a little bit colder though.

 

[dave4868]

Are you kidding??! Do you need to hear it from someone else that freshwater freeze up at 32F? It does... Put some salt in it and it'll keep kind off "flowing" a little bit colder though.

Exactly right!

Dave C

 

[Gary D.]

We were diving at about 4000 feet altitude. Both computers said 30. I know phase diagrams for fresh water show an initial decrease in freezing point with increased pressure but not that much. Just odd both computers would be off. I'll have to check again this weekend. Gary, were you doing an SAR dive or just recreational?

It would have been work if the three of them busted through. Where they were the ice is far from being ready but it was a short cut to the bar.

I would have been top side cuz I kind of got myself grounded for a while.

Gary D.

 

[DA Aquamaster]

It's time for calibration, I think. Get a bucket of ice water and several thermometers you think are accurate.

Not really surprising that the Suuntos would read the same. I'd be interested in hearing how far they are off.

I'll bet flowing freshwater can get close to 32F though. We need to hear from the prospecting river divers in Alaska....

Coldest freshwater I've seen has been 34F both under ice and in open water. Also saw as high as 37F under ice.

Dave C

Right idea but overly complicated. Assuming you use fresh water, if you mix a generous amount of ice and water in a bucket and wait a few minutes for the temperature to equalize, the water temp will be exactly 32 degrees and no thermometer will be needed.

Fresh water ice melts at 32 degrees and it takes a great deal of energy for the ice to undergo the phase change to water. Consequently as long as there is ample ice in the water and the two are not allowed to stratify, the temp will be 32 degrees.

So...dump a bag of ice in bucket, add water, wait a few minutes, put your console in and see then track the temperature to see 1. how much lag there is as the thermometer cools (the rate of change will probably get much slower as the temp approaches water temp) and 2. to see what the final temp is and how far it deviates from 32 degrees.

In my experience, the thermometers in dive computers are seldom accurate to more than a few degrees of the actual temperature. Changes in freezng point are not significant for normal atmospheric pressures and an altitude under 10,000ft should not make a significant difference.

------

As an aside, water becomes denser as it cools until it reaches 35 degrees F at which point it begins to expand. This is a fortunate event as if water did not expand and rise to the surface before freezing, bodies of water would freeze from the bottom up. This would mean that ice would not insulate bodies of water from colder surface air temps and would continue to freeze thicker all winter. The cold water over the ice (if any) along with a tendency for the coldest water to stay just over the ice would then insulate the ice underneath and greatly slow any thawing that would occur. The result would be that ice on the bottom of deep bodies of water would not melt and would eventually freeze all the way to the surface. Once this occurs, the light and heat reflected by the relatively light ice even under several feet of melt water, along with the loss of the oceans and large lakes as a natural heat sink, would reflect enough heat to turn planet earth into an ice ball in short order.

As it is, ice forms at the surface and insulates the water underneath greatly limiting the depth of ice that forms over a body of water and ensuring that ice quickly melts in the summer.

In short the expansion of water at 35 degrees, is one of the fortunate quirks of physics that makes life here possible.

 

[KOMPRESSOR]

Right idea but overly complicated. Assuming you use fresh water, if you mix a generous amount of ice and water in a bucket and wait a few minutes for the temperature to equalize, the water temp will be exactly 32 degrees and no thermometer will be needed.

Fresh water ice melts at 32 degrees and it takes a great deal of energy for the ice to undergo the phase change to water. Consequently as long as there is ample ice in the water and the two are not allowed to stratify, the temp will be 32 degrees.

So...dump a bag of ice in bucket, add water, wait a few minutes, put your console in and see then track the temperature to see 1. how much lag there is as the thermometer cools (the rate of change will probably get much slower as the temp approaches water temp) and 2. to see what the final temp is and how far it deviates from 32 degrees.

In my experience, the thermometers in dive computers are seldom accurate to more than a few degrees of the actual temperature. Changes in freezng point are not significant for normal atmospheric pressures and an altitude under 10,000ft should not make a significant difference.

------

As an aside, water becomes denser as it cools until it reaches 35 degrees F at which point it begins to expand. This is a fortunate event as if water did not expand and rise to the surface before freezing, bodies of water would freeze from the bottom up. This would mean that ice would not insulate bodies of water from colder surface air temps and would continue to freeze thicker all winter. The cold water over the ice (if any) along with a tendency for the coldest water to stay just over the ice would then insulate the ice underneath and greatly slow any thawing that would occur. The result would be that ice on the bottom of deep bodies of water would not melt and would eventually freeze all the way to the surface. Once this occurs, the light and heat reflected by the relatively light ice even under several feet of melt water, along with the loss of the oceans and large lakes as a natural heat sink, would reflect enough heat to turn planet earth into an ice ball in short order.

As it is, ice forms at the surface and insulates the water underneath greatly limiting the depth of ice that forms over a body of water and ensuring that ice quickly melts in the summer.

In short the expansion of water at 35 degrees, is one of the fortunate quirks of physics that makes life here possible.

Just a bit of correction. It's at 39F/4C which water have the highest density. Other than that, the rest is very accurate

When ice diving in lakes one will "always" find temps around 39F at the bottom, and colder further up underneath the ice. In our fiords there's an interesting phenomena as the water can be VERY cold on the surface. Perhaps 34-35F. With surface temps like these I've personally experienced 8C/46F at 30m/90ft in the Oslofiord! This is because salt water is even denser, and with no wind cold freshwater from rivers float out on the surface of the fiord like a carpet, not mixing with the warmer sea.