Saturday, August 31, 2013
Three Compartment Ocean
This brings me to a two compartment model by Steven Schwatrz with the Brookhaven National Laboratory. Dr. Schwartz use a simple RC two compartment model with the atmosphere/ocean mixing layer as the smaller compartment and the bulk of the oceans the second compartment. The way he divided the specific heat capacities he ended up with a roughly 8 year time constant for the atmosphere/ocean mixing layer and a roughly 500 year settling time for the bulk of the oceans. The object was to determine climate "sensitivity" and based on his rough model he came up with a ballpark of around 2C per doubling. Nice simple approach, nice solid results, nice simple model. The ~8 year time constant would be the equivalent of the noisy discharge static in terms of actual energy. The bulk of the Oceans would have about 800 times the capacity of the atmosphere/ocean mixing layer compartment.
In the Sketch above, I have a three compartment model for the bulk of the oceans. I am not concerned with the noise, just the energy. Since the southern oceans can more easily exchange energy, their time constant would be close to the 500 years that Dr. Schwartz figured. The northern hemisphere oceans cannot exchange energy as well with each other and thanks to the Coriolis effect, can't exchange energy that well with the southern oceans. As a rough estimate, the time constant for the northern Atlantic would be about 125 years and the time constant for the northern Pacific about 250 years based on just area and common equatorial forcing. With the northern Atlantic "charging" first, it would be the first to start a discharge by what ever convenient path it can find with a "likely" harmonic of tau(Atlantic)/2 or 62.5 years. The northern Pacific would "likely" have a 125 year harmonic and the southern hemisphere a 250 year harmonic. The noisiest signal would likely be the north Atlantic 62.5 year "oscillation". It doesn't matter what external forcing is applied, with unequal areas and limited heat transfer paths there will be some "oscillations" around these frequencies and the magnitude of the oscillations would be dependent on the imbalance between compartments. Most of the world land mass drains into the Atlantic, that energy varies with season and precipitation/ice melt, there will be constant thermal "noise".
Not that complex. Look at the big picture not the noise.