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Re: Obnoxious Oceans [
> I take it that there would be a (considerable?) degree of convective mixing
> under normal circumstances. When higher density, low latitude warm water
> stopped being added, the depths would also cool, reducing mixing. This
> would further reduce oxygen concentration at depths. Am I on the right
> track here?
No. Warm saline Mediterranian water forms a middle watermass across much of the
Atlantic basin. The water masses stay descrete for a remarkably long time.
North Pacific bottom water is about 10,000 years old as I understand it (last
time it say O2).
Water has a high heat capacity so it does not lose or gain heat rapidly.
> On the other hand, without polar caps, how do you substantially increase or
> decrease sea levels?
Changes in spreading rates along midocean ridges. The heat capacity of the
ocean crust is a constant. Warm crust is lighter, so with faster spreading
rates you have wider ridges displacing more seawater.
The Pacific ridge (rise) spreads about twice as fast as the Atlantic, thus it
has much greater volume.
For Cretaceous we have good record of spreading rate changes.