Winnipesaukee Forum - View Single Post

CanisLupusArctos · 04-03-2008, 11:13 AM

The air temp doesn't do much to melt the ice until it gets hot, like in the 70s or 80s. This is what I usually see happen: Sun heats the rocks, which in turn melt the ice away. The wind circulates the open water around which widens the hole. The lake receives some heat from the earth which is molten rock a few miles down, and it also receives heat from the sun which impacts shallow areas the most.

The lake is constantly trying to give off this heat. During the winter, that's no problem, so it freezes and the ice grows. When the air can't support that anymore, the equation gets tilted in the favor of warmer water, which melts the ice from below.

Last year when I installed the water temp monitor at the weather station I found that humidity plays a huge role in the water temp by regulating the evaporation rate. Evaporation cools things (that's how your sweat glands work - perspiration evaporates into the air, and the evaporation takes heat from your skin.)

The lake surface does the same. When it's cooling off you'll see the "heat loss fog" that is common in fall - that's water evaporating from the lake.

Warm air can hold a lot more humidity than cold air, and when there's already a lot of humidity in the air, it can't accept much from the lake (or your skin). Evaporation gets held to a minimum, and so the lake retains more heat (and so do you.) On a hot, humid day, the water temp will rise quickly. Here in the northeast we don't get hot *dry* days very often (it's more of a desert thing) but last May we did. It was in the upper 80s with very low humidity, and the water temp barely even budged. A few weeks later we got some weather that wasn't as hot, but it was really humid. The water temp shot up like crazy.

We all know the wind plays a big role in water temp by "stirring up the water" which happens when the wave action mixes surface water down. It also has the same effect as when you sit in front of a fan to cool off... moisture evaporates more quickly (this is what Wind Chill is all about) which carries the heat away.

So, what melts the ice is mostly water temp, and that's controlled by a whole bunch of things: Wind and humidity (the two biggest) followed by solar heat and geologic heat.

04-03-2008, 11:13 AM	#7
CanisLupusArctos Senior Member Join Date: Jan 2007 Location: Center Harbor Posts: 1,049 Thanks: 15 Thanked 472 Times in 107 Posts	The air temp doesn't do much to melt the ice until it gets hot, like in the 70s or 80s. This is what I usually see happen: Sun heats the rocks, which in turn melt the ice away. The wind circulates the open water around which widens the hole. The lake receives some heat from the earth which is molten rock a few miles down, and it also receives heat from the sun which impacts shallow areas the most. The lake is constantly trying to give off this heat. During the winter, that's no problem, so it freezes and the ice grows. When the air can't support that anymore, the equation gets tilted in the favor of warmer water, which melts the ice from below. Last year when I installed the water temp monitor at the weather station I found that humidity plays a huge role in the water temp by regulating the evaporation rate. Evaporation cools things (that's how your sweat glands work - perspiration evaporates into the air, and the evaporation takes heat from your skin.) The lake surface does the same. When it's cooling off you'll see the "heat loss fog" that is common in fall - that's water evaporating from the lake. Warm air can hold a lot more humidity than cold air, and when there's already a lot of humidity in the air, it can't accept much from the lake (or your skin). Evaporation gets held to a minimum, and so the lake retains more heat (and so do you.) On a hot, humid day, the water temp will rise quickly. Here in the northeast we don't get hot dry days very often (it's more of a desert thing) but last May we did. It was in the upper 80s with very low humidity, and the water temp barely even budged. A few weeks later we got some weather that wasn't as hot, but it was really humid. The water temp shot up like crazy. We all know the wind plays a big role in water temp by "stirring up the water" which happens when the wave action mixes surface water down. It also has the same effect as when you sit in front of a fan to cool off... moisture evaporates more quickly (this is what Wind Chill is all about) which carries the heat away. So, what melts the ice is mostly water temp, and that's controlled by a whole bunch of things: Wind and humidity (the two biggest) followed by solar heat and geologic heat.