Winter observation

Nick Guilbert teaches Science at Peddie, and has been a resident of Hightstown since 1984. He is also a photographer, and noted some interesting and very beautiful observations about Peddie Lake last week.

As Peddie Lake has thawed since the cold snap, its surface has had striking bright and dark variations, like lanes or stripes on the surface of the lake.  The white/bright lanes are ice and snow covered; the darker lanes are liquid water.  I've never seen a lake thaw that way before - like an artist painted bold black-and-white stripes on the surface of the lake.

It seemed to me that the lanes indicate where water is/was flowing most heavily, or most quickly, under the icy surface of the lake.  Those under-the-surface currents would erode the ice cover from below more thoroughly, so as the weather warmed, those channels would melt first since the ice became thinner there.  In other words, my thinking was that the dark lanes on the lake serve as an ex-post-facto map of the lake's under-ice currents while it was frozen.

After a little bit of research, I found that the lanes are indeed due to the lake ice melting from the underside first.  That's the part I got right. But it turns out that the melting-from-below happens because of heat convection in the waters below, not from currents flowing and eroding the underside of the ice.  Once the snow on top of the lake either melts or blows off, the ice sheet is transparent enough to conduct sunlight into the water below and warm it up.