Over what time period? The Isthmus of Panama, for example, developed some 40 million years ago; before there was a connection between the two Americas, the oceanic circulation must have been significantly different, with a concurrently different distribution of the heat budget.

I thought that the ocean was a major part of climate, a factor but not a distinct actor.

http://www.physicalgeography.net/fundamentals/8q_1.html

A relief map of the Atlantic Ocean floor:

http://shop.nationalgeographic.com/product/4339.html

Don’t know if that’s what you were looking for.

http://www.newscientist.com/article/mg20026814.100-sunspot-activity-linked-to-earth-riverflow.html

That is the prevailing theory.

I am simply wondering if that trigger might be a major change in tropical Atlantic (or maybe even somewhere else) currents when ocean levels reach a certain point.

Could be. Land configuration is a significant factor. The theory doesn’t exactly explain how the ice forms (then leads to albedo feedback), merely that it does.

While orbital mechanics might be an “enabling” mechanism, something must act as a trigger (in both directions). I am simply wondering if that trigger might be a major change in tropical Atlantic (or maybe even somewhere else) currents when ocean levels reach a certain point. So do oceans rise until Florida is flooded causing the “Gulf Stream” not to be channeled around the end of Florida forming a stream? Do oceans drop until the stream is basically cut off? Is that the “trigger”? And even then I would think it would be a gradual change. Whatever happens seems to happen quite dramatically. In the space of one modern human’s lifetime we go from maximum cold and glaciation to the warmest period of the interglacial. The contrast in temperatures over only a couple of hundred years is simply amazing and something that is counter-intuitive to me if orbital changes are the cause of it.

Not unlike IPCC tipping-point theory.

There is an argument over which is more of a primary driver, obliquity or eccentricity. (There are some inclination fans as well.) The reason for this is that at one point, ice ages were occurring every c. 50,000 years and before that ever 100,000. Others argue that it is not one driver but a conjunction which causes the feedback loops.

Orbital changes happen gradually over long periods of time. Changes from glaciation to interglacial happen practically instantly on a geological timescale. I wonder why. Could a general cooling slowly lower ocean levels until the gulf stream changes in some significant way and causes less heat to be transported Northward and suddenly the entire North Atlantic climate changes? During ice ages, what is the delta in temperatures in North Atlantic climates vs North Pacific climates? Does the Atlantic make an extreme change and the Pacific not change much at all? Why do things suddenly warm up out of glaciation for about 10K years and then go back to the “normal” glaciation state?

I am curious what I might find if I am able to gradually drop sea levels. How does the Gulf Stream react and is there a certain point where things succenly change.

Thanks but things have drifted somewhat and continents have different shapes, etc. Basically what I would want to do is pull the shoreline down to the 100 meter sea floor contour line and have a look. I am guessing that a lot would change. A lot of land area in the Caribbean would become exposed. How would that change the path of the Gulf Stream? Would the stream get “split” somewhere? It certainly would change tropical storm behavior in the region with much more land area storms would behave differently.

What I would be most interested in is if the stream gets pushed considerably farther East before heading into the Atlantic and if it might become split by some landmass in its path. Or does the amount of water available for the current become reduced greatly because of considerable shallowing of the path? Basically I just want to see what that region looks like with the ocean level 100 meters lower.