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Originally Posted by ewitte
I heard before that if enough ice melts somewhere (not sure where) it would actually trigger an Ice Age not warming. I'm also recalling off of memory the warm periods usually do not last that long.
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You are correct. When enough ice melts, seawater will become less dense and we will no longer create the deep-water seawater that drives the ocean circulation system. That is already beginning to happen as is evidenced by the increasing frequency of El Nino. Interglacial periods typically last 10 -15k yrs--we are somewhere around 12-13k into the current interglacial period. It is the warming that leads to the ice melt and then the shut-down of the circulation system that is believed to have driven the glacial/interglacial cycles over the past 600k yrs. The warming starts as a result of a combination of changes in our orbital path and the wobble in our axis, CO2 released naturally in the warming process then enhances and extends the warming, but now we are way beyond the historical CO2 concentrations.
I think that once the ocean circulation system shuts down, there will be some rapid climate change, initially causing a rapid warming, followed by increased snowfall that will start a glacial cycle.
Edit, BTW it is the North Atlantic that is the source of Deep-Water formation, so ice melt or decrease in formation of Ice in the North Atlantic is what will slow or stop the ocean circulation system.