I'm certainly new to all this but don't forget that if you are moving lower water up with aeration that the water that's moving up is replaced by water residing elsewhere in the pond. While it's not directly pulling water from the surface down it certainly would seem to imply that if one looks at all the diagrams that aeration companies put out on how aeration destroys the stratification layer.
When initially starting up the upwelling water would be colder than the surface water and would tend to sink back down faster but it will at the same time be mixing with the warmer surface water. However the average temperature should be lower than the unmixed surface water and so it should still sink - moving some of the mixed surface water down to the lower depths.
That process would probably continue until the BOW is at a more or less uniform temperature with little to no stratification. No clue where the water to replace the upwelling water comes from at that point but the fancy diagrams suggest the cycle just continues with surface water falling to the lower regions - which may be the case when the water cools in the evening. During the heat of the day it probably just continues to look like a blender.
Just my $0.02 but not based on any real science.
