When Redwood Forests Grew In Arctic Canada-What Were The Tropics Like?

[ralph124c]

The fossil forests found on Ellesmere Island are over 100 million years old. Clearly, the average world emperature was much higher back then. My question-what were the equatorial regions like back then? Were they jungles or vast deserts?

[Diceman]

I expect some of both, depending on how far away large bodies of water were. Tropical temperatures probably would have been almost unbearable by human standards. Back then, even the high arctic was temperate enough (in the summer, at least) to support large colonies of grazing dinosaurs.

[wevets]

100 million years ago was the middle of the Cretaceous period, and the tropics were paradoxically only around 22-30°C, estimated from fossilized plants and shells of marine invertebrates, versus the poles, which were much warmer than present (although still colder than the Cretaceous tropics.)

@wikipedia

A very gentle temperature gradient from the equator to the poles meant weaker global winds, contributing to less upwelling and more stagnant oceans than today. This is evidenced by widespread black shale deposition and frequent anoxic events.[18] Sediment cores show that tropical sea surface temperatures may have briefly been as warm as 42 °C (107 °F), 17 °C ( 31 °F) warmer than at present, and that they averaged around 37 °C (99 °F). Meanwhile deep ocean temperatures were as much as 15 to 20 °C (27 to 36 °F) higher than today’s.[19][20]

If you’d prefer a source other than wikipedia: Paleoclimatology | National Centers for Environmental Information (NCEI)

For example, 100 million years ago, the Earth’s temperature was 20° - 40° Celsius warmer (or 36 ° - 72 ° F) in the polar regions, although only a few degrees warmer around the equator. Evidence suggests that during warm Cretaceous periods, levels of atmospheric carbon dioxide were high. (Barron, et. al., 1985.) Models indicate that carbon dioxide may have been four to six times the pre-industrial levels. (Otto-Bliesner, et. Al., 2001.)

There’s a wikipedia page about the cool tropics paradox with some good references linked at the end.

[engineer_comp_geek]

The polar ice has melted and on more than one occasion there has been plant and animal life there. In the time you are talking about, just as the wikipedia article says, the temperature difference between the poles and the equator wasn’t as great as it is today. Also, the overall temperature of the earth was higher than it is today, but that’s true of most of earth’s history. We’re in an unusually cold period right now, and have been for the last 30 or 40 million years or so. Then again, at one point the entire earth nearly froze solid (google “snowball earth” for more details on that one), so we’re not in the worst cold spell Earth has ever seen. Not even close.

At other times, the ice caps have been melted away, but the temperature difference between the poles and the equator was much greater, resulting in large scale extinctions around the equatorial regions (at least on land, the oceans didn’t fare quite so badly, I believe). These types of conditions are thought to have been present around the end of the Permian–Triassic extinction event (aka the Great Dying) roughly 250 million years ago. There was a lot of other stuff going on at the time (highly acidic seas, volcanism, possibly a large impact event of some sort) so it’s hard to say exactly how much each of those factored into the Great Dying.

[snowthx]

Is it possible that the island was further south 100 MYA?

[Blake]

@snowthx

Is it possible that the island was further south 100 MYA?

Maybe.

However there were deciduous beech trees growing on the mountains in Antarctica within the past few million years. We know that Antractica has remained well within the Antarctic Circle for the past 100 million years at least, and 3 million years ago would have been within a few kilometres of where it is today.

So we know that polar temperatures were much higher in the recent past than they are today. How much warmer we don;t know for sure. Some researchers claim 50oC warmer, some claim 12oC warmer. Either way, much, much warmer than today and much warmer than the worst climate change predictions.

[md2000]

IIRC the area from the Gulf of Mexico to the arctic along the rockies was a shallow sea. (It’s legacy is oil and oil shale all up and down its west coastline following the Rockies). I kind of wonder if part of the climate situation back then was the equivalent of a gulf stream running up through the center of North America to feed warm water into the arctic.