Saturday, April 19, 2014

Thermodynamics 001 (for Judy and Lumo)

Judy Curry and Lumo think that the second law of thermodynamics prevents heat deposited in the deeper ocean from warming the surface. They know, I assume, that net heat flow between bodies at different temperature is from warmer (surface) to cooler (deep ocean), but, in yet another example of a little knowledge being a dangerous thing, they assume that that means that adding a little heat to the deep ocean won't warm the upper ocean. That's not true.

If you put on a jacket on a cold winter day, you will probably be warmer than you were without it, even though the inside of the jacket is colder than your skin. The point is that it's not as much colder than your skin as the outside air is. This is a ubiquitous theme in atmospheric physics - cirrus clouds a lot colder than the ground moderate winter surface temperatures because they are a lot warmer than outer space.

The same principle applies to warming the deep oceans - even though net heat flow will still be downward, it will be less when the subsurface is warmer.

Probably more important, though, is the effect of deep ocean warming on densities and the dynamics that drive ocean circulation.

Another freshman physics error for our dynamic duo, probably more egregious for a supposed atmospheric physicist who really really should know this. String theorists, not used to dealing with anything in the the real world, have a slightly better excuse.