> On Aug 19, 7:20 am, Bryan Heit gmail.com> wrote:
>

>> Most likely explanation is that the lake was undergoing a turnover.
>> Here in the north this usually occurs in the spring and fall, and it
>> plays a central role in the ecology of most lakes.

>

>> Basically, what happens is over the summer you get a layer of warmer
>> water over the layer of colder water.  By the end of summer this warm
>> layer tends to be quite thick.  When fall comes (or a cold front, etc)
>> the upper layers of water cool, faster then they sink.  This creates a
>> layer of colder water at the surface.  Eventually the sinking of this
>> cold water will mix the whole lake, but for brief periods you can have
>> a colder surface than the layer immediately underneath it.

>
> Sure, in Canada maybe, but how cold does it get in Australia?