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Posts: 619
Location: Verona, WI | I am going on a dive trip to Cozumel in January and did a couple of dives yesterday on Lake Wazee to shake the rust off a bit. Surface temp was 55 degrees but as we got down to the 60' level the water reached 40 degrees. That got me thinking. Turnover occurs at the time when the water temp on a lake is warmer at the bottom than the top so the water from the bottom rises and mixes with the water from the surface. The mixing causes water temps to equalize across the lake.
Given that big temperature difference in the lake it had not turned over because the water temp was not consistent. Is it possible that some deep clear lakes don't turn over or that the turnover occurs so late in the year (when surface temps get to that 40 degree level) that we just don't see much of it?
Shane |
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Location: Yahara River Chain | Shane you could be right as in the sense as we as muskie anglers define it. While deep clear lakes stratify, fish can be below the thermocline (lake trout, cisco, etc) as the oxygen does not deplete enough because of the lack of decomposition of matter in those depths. If that is the case, then the mixing we see on say the Madison Lakes does not happen. We do see junk floating up and smell with the flip here and I would think that would not be noticed on a deep clear infertile lake.
The real question is what is turnover? Is it when the temps of the lake the all the same? Or is it when the oxygen is the same throughout the depth of the lake?
Good topic!
Edited by muskie! nut 10/26/2008 3:18 PM
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Posts: 83
| Enjoy that trip to Cozumel Shane! It's one of my favorite dive destinations. I don't know if all lakes turn over, but I would bet that some don't. I would say that there would be a point where the water is all the same density, but it would take current or wind to mix it. Say some very heavy 39 deg water was at the bottom of a 20 acre quarry. I'll bet it stays down there for ages.
http://muskie.outdoorsfirst.com/watch.asp?id=1084 |
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Location: Rhinelander, Wisconsin | Cool surface water sinks as it is denser than the warm water below, displacing the warmer water that rises, as it is less dense. Temps throughout the water column equalize; once that has happened, the lake has 'turned over'. This process continues and is effected by wind mixing and other variables throughout the fall and even winter. The densest water is at 39 degrees.
If the lake has stratified and there is an effective thermocline with low oxygen, 'turnover' removes that layer and mixing allows the fish to move throughout the water column, about anywhere, in reasonable comfort.
Here's a great link.
http://waterontheweb.org/under/lakeecology/05_stratification.html
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Posts: 2894
Location: Yahara River Chain | I found this on another web site
"So, in theory, when the surface temps continue to cool the cooler water will sink, displacing the warmer water. When the temp below the thermocline is the same as above it the lake is ready to roll. With some strong winds it'll happen. Keep in mind that temp is only a part of rollover, the dissolved oxygen is the key. Having the same temp throughout the water column is meaningless until the deleted oxygen supply is refreshed from the surface waters." |
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Location: Verona, WI | So then on this lake where the bottom layer (or at least as far as I dove) was 40 degrees, turnover won't occur until the surface water temp reaches 40 degrees? If that's the case doesn't that mean that the deeper lakes may turn MUCH later than most of us think? There are a lot of implications if that's the case as I would guess this lake won't hit 40 degrees for another month. If this happened on a deep musky lake we could be fishing way to shallow.
Shane
Edited by ShaneW 10/27/2008 3:39 PM
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Posts: 567
| I used the cozumelmycozumel.com website for info on lodging, food diving, etc etc -- food reccomendations were excellent ! MD |
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Posts: 83
| The surface temp does not always have to drop to 39 for a turnover to occur, although this is probably the most common. In September 2006 a strong sustained east wind blew over lake Erie for several days. the surface temp was nearly 70, but the sustained winds pushed the surface layer toward Toledo. As the cool water welled up, it dropped the lake temp by about 20 deg at the eastern end.
So, with our thin wetsuits, no hoods or warm gloves, our crew embarked on our annual last group dive and ensuing party. It's a big deal for us, deep fried turkeys, everybody brings a dish, plenty of liquor, you know. The surge of icy fun hit the Niagara about the same time we were rolling in. Plenty of yelling and swearing. I had volunteered to run one of the boats for the first dive, and hit the water on the second and third drifts. Well, that one drift was the end of the diving. No way am I plunging into 52 deg. water with a 3mil. and a licra hood.
So, even though they painted my big toenails purple as I dosed in my bag chair after Turkey and BV, it was a lot better than actually having ALL MY NAILS TURN PURPLE from the cold. |
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Location: Southern W.Va. | Very interesting stuff. My question is this , " Does a shallow , 300 acre, max depth 13 feet, still go thru the turnover process or does the wind keep things in balance from top to bottom?" |
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| Mauser, I'd think a lake that shallow would never stratify during the warmer periods, and therefore no turnover would occur.
Edited by esoxaddict 10/30/2008 12:33 PM
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Location: Grand Rapids, MI | jimkinner - 10/27/2008 6:51 PM The surface temp does not always have to drop to 39 for a turnover to occur, although this is probably the most common. In September 2006 a strong sustained east wind blew over lake Erie for several days. the surface temp was nearly 70, but the sustained winds pushed the surface layer toward Toledo. Jim - I'm sure the lake was still stratified though. In fact a thermocline probably would increase the effect of the cold water upwelling. Lake Erie is known for it's seiche effect which can drop the water on the west end a couple feet during sustained winds. |
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Location: Grand Rapids, MI | Mauser - 10/30/2008 11:22 AM Very interesting stuff. My question is this , " Does a shallow , 300 acre, max depth 13 feet, still go thru the turnover process or does the wind keep things in balance from top to bottom?" Since there isn't a thermocline it doesn't technically "turnover". Unless it is spring fed there is usually a layer of water, even in shallow lakes, that the wind doesn't mix that is low oxygen and usually much cooler than the surface. |
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Posts: 83
| I'm sure the lake was still stratified though. In fact a thermocline probably would increase the effect of the cold water upwelling. Lake Erie is known for it's seiche effect which can drop the water on the west end a couple feet during sustained winds.
You are correct Will. A surface thermocline would set up. Similar to the kind of break that is fished for salmon and trout in the spring.As the wind eased, and shifted, the colder water would sink again, and the warmer water at the west end would spread over the the surface of the lake again. It is a more common occurance on lake Ontario. It did cause a big fish kill on the east end of Erie, though.
http://muskie.outdoorsfirst.com/watch.asp?id=1084 |
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| Shane,
I've been down there a ton, most recently this past May. Cozumel remains that crappy little Mexico that most of us fell in love with. Stay the hell away from Playa Del Carmen at all costs, unless you want to get shaken down every 2' for time share purchase, scooter rentals, excusion rentals and gringo mexican food. The place has gone crazy. I like my Mexico crappy and cheap, not European and expensive.
A little heads up, the deeper dives like Santa Rosa are a bit better nowadays due the hurricane a few years back beat up the shallower reefs. If for some reason you decide to hit the Playa side, make sure you dive the Cenotes. The excursion BS may wear you out, but diving the caves is pretty unique.
I have a friend down there who runs the dive operation for Iberostar, if you are happen to be staying at one get back to me, I can save you so $. |
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| Just because the lake turns over doesn't mean the temp will be the same throughout. It only means that the thermocline breaks open, and that the water has mixes to a certain extent. Think about it ... the sun hits the water and warms it up on top, but it isn't going to warm the bottom. Just because it's warmer near the surface doesn't mean the lake is still stratified. |
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Do deep clear lakes really turnover?