Thread: Thermocline

I noticed what I now think is the thermocline on my home lake on my new Helix 8. This is the first unit I've had that has DI and SI and I could see the feature on both. This is a shallow lake and the deepest point I've found so far is around 23 feet. Is there a minimum depth at which a thermocline would form? Also, I assume that the thermocline could show up in different areas of the lake, but in areas that are deep enough for the separation to form?

This is a good thread.

If there is no water movement it can form pretty shallow, usually will not form in a main channels that has frequent movement like from hydro-generation and such. I had jug lines out one year about 50 yards from the channel set at 20 and pulled up 4 dead cats all around 5 lbs. but the channel was pulling water so it can be a very fine line as too where it is and where it isn't.

Originally Posted by Sickle Hook

Here are my thoughts on the the OP image.
Im thinking that graph is showing only the top
portion of the thermocline. The bottom edge
of the thermocline is deeper than the 28.8 ft
shown on the graph, therefore we would have
to move out to deeper water to see the
bottom of the thermocline and the cool layer
of water underneath it.
SH

Thermoclines from when the density of hot water and cold water differ. The change in water temperature occurs rapidly in a a short depht change. Water will be warmer at the top and slowly cool down as you go deeper. When you hit the thermocline the water temperature and density will change rapidly within a ft or two. Unless there is a current the thermocline will separate the bottom water from the surface water.

As I diver I've hung in the water column vertically with my head above the thermocline and my feet below the thermocline. I required a full wet suit when diving belong the thermocline in freshwater lakes in the hot summer months. I also liked to dive off the diving boards and would often dive down to the bottom of the lake. It was very cold on the bottom and when coming back up you could easily feel the water warming up above the thermocline. Some lakes have two thermoclines. Some at 12 ft and the other at 25 ft or so. It depends on the water quality and the depth of the lake. Now running waters mix the water up so that thermoclines don't always form.

Some of the old stripper pits that I used to dive in where 60 ft deep and had a thermocline at around 25 ft and below that depth, the water was dirty and orange colored. We never went below the thermocline in that pit. It was clear for 100 ft at times above the thermocline and all the fish were swimming above the thermocline. Lots of sunfish swimming around 10 to 15 ft deep way above the thermocline.

The thermocline is not very thick. It's where the temperature of the water changes by more than a few degrees in just a foot or so of water depth. So the thermocline does not extend way down to the bottom. That area below the thermocline is called the hypolimnion. The area above is called the epilimnion. Most aquatic fish life lives above the thermocline during the hot summer months. After the thermocline breaks up and the oxygen mixed down into the hypolimnion again then fish can enter the deepwater again dn spend time down on the bottom of the lake in the cold winter months.

Originally Posted by tstone

Is the drop-off a creek channel? Reason I ask is that on one of the lakes I fish I found an almost identical scenario and it was "within" the edges of a small creek channel (if that makes sense). Looked liked a thermocline layer but shouldn't have been one within the current of the channel, or at least I don't think it would.

All you can tell is that the transducer was over shallow water and moved out over deeper water. It could have been the shoreline or a creek channel edge or an underwater hump or island. Unless the OP gives us more information about the area he was going over we won't know for sure.

If there is a strong current there won't always be a thermocline as the current will mix the deeper water with the surface waters and break up any thermocline.

Originally Posted by Moveon

All you can tell is that the transducer was over shallow water and moved out over deeper water. It could have been the shoreline or a creek channel edge or an underwater hump or island. Unless the OP gives us more information about the area he was going over we won't know for sure.

If there is a strong current there won't always be a thermocline as the current will mix the deeper water with the surface waters and break up any thermocline.

I was just moving out from the shoreline to deeper water.
Thanks
SH

Originally Posted by Sickle Hook

Hey Redge. Can you show an image
Of thermocline on si?
Thanks SH

I’ll try and get one this weekend!


Sent from my iPhone using Crappie.com

You can see some faint lines on the SI here...it was on auto that's why it's at 300 feet.

Can you give us your thoughts on
What’s happening in the OP image? Is it
a thermocline? I’m here to learn.
Thanks SK

Originally Posted by Moveon

Thermoclines from when the density of hot water and cold water differ. The change in water temperature occurs rapidly in a a short depht change. Water will be warmer at the top and slowly cool down as you go deeper. When you hit the thermocline the water temperature and density will change rapidly within a ft or two. Unless there is a current the thermocline will separate the bottom water from the surface water.

As I diver I've hung in the water column vertically with my head above the thermocline and my feet below the thermocline. I required a full wet suit when diving belong the thermocline in freshwater lakes in the hot summer months. I also liked to dive off the diving boards and would often dive down to the bottom of the lake. It was very cold on the bottom and when coming back up you could easily feel the water warming up above the thermocline. Some lakes have two thermoclines. Some at 12 ft and the other at 25 ft or so. It depends on the water quality and the depth of the lake. Now running waters mix the water up so that thermoclines don't always form.

Some of the old stripper pits that I used to dive in where 60 ft deep and had a thermocline at around 25 ft and below that depth, the water was dirty and orange colored. We never went below the thermocline in that pit. It was clear for 100 ft at times above the thermocline and all the fish were swimming above the thermocline. Lots of sunfish swimming around 10 to 15 ft deep way above the thermocline.

The thermocline is not very thick. It's where the temperature of the water changes by more than a few degrees in just a foot or so of water depth. So the thermocline does not extend way down to the bottom. That area below the thermocline is called the hypolimnion. The area above is called the epilimnion. Most aquatic fish life lives above the thermocline during the hot summer months. After the thermocline breaks up and the oxygen mixed down into the hypolimnion again then fish can enter the deepwater again dn spend time down on the bottom of the lake in the cold winter months.