Palm phytoliths in subarctic Canada imply ice-free winters 48M years ago | Hacker News Reader

Palm phytoliths in subarctic Canada imply ice-free winters 48M years ago

academic.oup.com

40 pointsStratoscope17 comments

The equable climate problem reminds me of the exoplanetary curiosity of the tidally locked planet. For a long time, people expected that all such planets would have an atmosphere that inevitably crashed out as ice on the cold side, rendering them uninhabitable.

More recent computer models of convection suggest that many such worlds would have sufficient convective activity, cycling between altitudes from one side of the planet to the other, to maintain gasses and liquids on the surface.

To match the observations, a model simply requires something about higher CO2 levels which specifically encourage hygrothermal exchange between poles and equator, and/or significantly insulates the poles against radiative losses in disproportionate ways versus today. CO2 itself doesn't seem likely to cause this because it's in the gaseous phase for almost all of Earth's history, but substantially increased water in the atmosphere would be the first suspect because water is such a strong thermal reflector when a cold liquid, and not so much when a gas.

it would require a very specific configuration not to freeze out, high greenhouse gasses, world spanning oceans, and continental masses that directed ocean and atmospheric currents, all located in a very tight circular orbit, just the right distance from the star. Given that a tidaly locked planet, means a VERY old system, it becomes improbable that conditions for maintaing an atmosphere and water over the radicaly different conditions that the planet experienced on its way to being tidaly locked can be described. so, modeling the steady state condition is possible, but there is no way to model the process that created it.

Popularized summaries:

Study reveals palm trees once thrived in subarctic Canada

https://www.eurekalert.org/news-releases/1074307

New study reveals Canada’s subarctic was once a tropical paradise

https://www.ctvnews.ca/sci-tech/article/new-study-reveals-ca...

What would the equator have been like at this time? Too hot for human life?

more info https://en.wikipedia.org/wiki/Eocene_epoch

For some reason, the temperature difference from the poles to the equator was much smaller at that time than it is now. Explaining why is an open challenge known as the equable climate problem.

https://en.wikipedia.org/wiki/Eocene#Equable_climate_problem

> BAYSPAR measurements indicate extremely high sea surface temperatures of 40 °C (104 °F) to 45 °C (113 °F) at low latitudes,

I'm going to take a wild guess that humans aren't doing so good near the equator with 45°C oceans. Though it's definitely interesting that the temperature gradient flattened out so much.

Kingdoms in the poles, wasteland in the middle. No wonder why Canada and Greenland became targets.

https://landtrustalliance.org/blog/as-temperatures-rise-farm...

"As temperatures rise, farms are sprouting in Alaska

Even as farms decline across the U.S., a longer growing season is bringing food security to a state that has long relied on sustenance from afar."

The kimberlite source of these phytoliths and their age makes me question our confidence in their origination from the arctic surface. Is it at all possible this material was cycled through plate tectonics which subducted it from a southern source and eventually ejected far north through volcanic action? I mean, a lot could happen over 48M years...

The sort of trip it would need to go through to make that journey doesn't make survival of the fossil very plausible.

Even a 'microscopic siliceous structure', which is what they're talking about here? To be clear, I am in no position whatsoever to challenge your statement, just curious as to why it would be unlikely for something invisible to the human eye to be shifted around the planet via plate tectonics (which seems entirely plausible to the layperson that I am).

Perhaps that part of subarctic Canada was at a completely different latitude 48M years ago, quite separate from continental drift.

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

Are you suggesting the earth flips around like the tennis racket?

about 500km from today's position (1cm/year drift).

https://images.theconversation.com/files/325868/original/fil...

How many flights were people allowed on back then and how much carbon tax did they pay?

0 and $0, therefore we should require a minimum of 20 flights at a tax of $5,000 each to guarantee the opposite effect! Of course, perhaps it's less about where the CO2 came from and more about how much is in the air. The former was a bit more fun to think about though :).

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