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Comment by mistrial9 | Hacker News Reader

Is it true that only 30,000 years ago the level of the sea was very different? lower in that case, exposing the land bridge at Alaska, and connecting the Islands north of Australia.. and previous to that, the sea level was much higher? evidence is the inland sea that is California Central Valley..

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The past 5000 years have been quite stable, but there have been dramatic changes from melting ice caps before that. See https://commons.m.wikimedia.org/wiki/File:Post-Glacial_Sea_L...

With a high enough warming rate, we might get a chance to see what a "meltwater pulse" looks like :-/

Yes, there has been a cycle going on in the most recent era of flipping between glaciers growing and shrinking. I don't recall the actual date but the most recent maximum glacier coverage was on the order of 30,000 years ago. The whole of human civilization we know about more or less happened since the last retreat of the glaciers.

There have also been times when the polar caps melted completely and there were rainforests pole to pole.

If you go back tens of millions of years ago there were dinosaurs in polar regions. Of course it was much warmer then

https://www.smithsonianmag.com/history/the-strange-lives-of-...

https://en.wikipedia.org/wiki/South_Polar_region_of_the_Cret...

The dinosaurs in the polar reason isn't because it was warmer, it's because the Strait of Magellan were closed.

One of the reasons we are in an ice age right now (which refers to a period where you have periodicly advancing and retreating glaciers) is because you have a continent on the pole and a clear sea lane around it, before the Strait of Magellan opened you have a current that circulated between the poles and equater evening out the temperatures allowing for ice free poles.

The same three atmospheric cells exist in the northern hemisphere and there is no continent there. Why is that?

https://en.wikipedia.org/wiki/Atmospheric_circulation

Those are different, this is about water circulation not air circulation, water has a much higher specific heat so it it's far more important when it comes to temperature circulation.

Humans evolved under much warmer conditions than exist today

Modern sea level is the highest it's been in over 100k years. Central valley hasn't been anything close to an inland sea for about 1.5m years, but that has more to do with deposited sediment than sea level.

Yes, there is periodic cycle, depending on ice ages.

I don’t see how given the Earth is only 6000 years old.

And flat, so any excess water will just run over the edge.

Good thing turtles are OK getting wet.

If they can put up with elephants standing on their backs then a bit a water is clearly not going to bother them.

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