Well, it's tricky, isn't it bz? However, I was guessing that there was enough ice off to allow the circulation to equalize the water temps from top to bottom.
Dave - You are correct in your guessessment about the amount of circulation causing the equalization. With the influx of 4,000,000 plus gallons of ground water and the circulator running 24/7 there has been a lot of mixing occurring.
