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wd40
2012-Sep-13, 06:03 PM
If the Earth was 10 degrees warmer 40 million years ago, how can the Antarctic have been as lush as a jungle http://www.newscientist.com/article/dn22253-lush-antarctic-past-suggests-more-monsoons-in-future.html if the Sun was below the horizon for 1/2 the year?

Is direct sunlight required for a verdant flora?

NEOWatcher
2012-Sep-13, 06:31 PM
If the Earth was 10 degrees warmer 40 million years ago, how can the Antarctic have been as lush as a jungle http://www.newscientist.com/article/dn22253-lush-antarctic-past-suggests-more-monsoons-in-future.html if the Sun was below the horizon for 1/2 the year?

Is direct sunlight required for a verdant flora?
They don't make it clear what kind of flora they found other than relating it to seasonal rainfall.
If I had to take a wild guess, it would have been flora that goes dormant in the winter and bounces back in the spring.

starcanuck64
2012-Sep-13, 06:32 PM
If the Earth was 10 degrees warmer 40 million years ago, how can the Antarctic have been as lush as a jungle http://www.newscientist.com/article/dn22253-lush-antarctic-past-suggests-more-monsoons-in-future.html if the Sun was below the horizon for 1/2 the year?

Is direct sunlight required for a verdant flora?

You need some sunlight for photosynthesis.

Antarctica was much warmer 40Mya ago and before, but it did have cold winter conditions when the sunlight wasn't present.

I'm pretty sure it was like NEOWatcher states, the plants went through a dormant stage when the temperatures dropped and the sun dropped below the horizon.

Also according to this article, the tropical vegetation on Antarctica was limited to the coastal region where the temperatures were warmer.

http://www.sciencedaily.com/releases/2012/08/120801132339.htm


In an area where the Antarctic ice sheet borders the Southern Ocean today, frost-sensitive and warmth-loving plants such as palms and the ancestors of today’s baobab trees flourished 52 million years ago. The scientists’ evaluations show that the winter temperatures on the Wilkes Land coast of Antarctica were warmer than 10 degrees Celsius at that time, despite three months of polar night. The continental interior, however, was noticeably cooler, with the climate supporting the growth of temperate rainforests characterized by southern beech and Araucaria trees of the type common in New Zealand today. Additional evidence of extremely mild temperatures was provided by analysis of organic compounds that were produced by soil bacteria populating the soils along the Antarctic coast.

wd40
2012-Sep-13, 06:54 PM
Was the length of a day, a season and the 23 degree angle any different 50 million years ago?

ravens_cry
2012-Sep-13, 07:02 PM
Wasn't Antarctica a bit closer to the Equator back then as well?

NEOWatcher
2012-Sep-13, 08:04 PM
Wasn't Antarctica a bit closer to the Equator back then as well?
I questioned that myself and tried to find a clear map of the continental drift for then. I can't say for sure, but what I did find seemed to indicate most of Antarctica was already within the Antarctic circle 40MYA.

Rhaedas
2012-Sep-13, 09:30 PM
Antarctica was almost half in the the Antarctic circle when it was part of Pangaea. It didn't move as much as other continents.

http://www.suntrek.org/images/DRIFT1.gif

starcanuck64
2012-Sep-13, 09:52 PM
According to the article posted above, the ocean currents around Antarctic probably would have been very different. Instead of isolating and insulating the continent they delivered a lot of warmth.


These new findings from Antarctica also imply that the temperature difference between the low latitudes and high southern latitudes during the greenhouse phase 52 million years ago was significantly smaller than previously thought. “The CO2 content of the atmosphere as assumed for that time interval is not enough on its own to explain the almost tropical conditions in the Antarctic”, says Pross. “Another important factor was the transfer of heat via warm ocean currents that reached Antarctica.” When the warm ocean current collapsed and the Antarctic coast came under the influence of cooler ocean currents, the tropical rainforests including palms and Baobab relatives also disappeared.

John Mendenhall
2012-Sep-13, 10:17 PM
Antarctica was almost half in the the Antarctic circle when it was part of Pangaea. It didn't move as much as other continents.

http://www.suntrek.org/images/DRIFT1.gif

IIRC, yes, very depressing. Been stuck down there near the pole for a long time. Wonder if any dinosaurs there survived the KT extinction?

slang
2012-Sep-13, 10:47 PM
IIRC, yes, very depressing. Been stuck down there near the pole for a long time. Wonder if any dinosaurs there survived the KT extinction?

You're being orientationist! It might just as well enjoy the heck out of staying up there. ;-)

starcanuck64
2012-Sep-13, 11:00 PM
I believe the new "fact" I posted earlier today explains why Antarctica has stayed where it is for so long.;)

http://cosmoquest.org/forum/showthread.php/115699-We-don-t-need-no-stinkin-Untrue-Facts!-(!!!)?p=2063532#post2063532

Rhaedas
2012-Sep-14, 12:15 AM
You may be partially right. If hot spots break up super continents and drive the movement, then if hot spots also tend to concentrate more towards the equator, it would make sense that a continent that migrates into the cold areas, the poles, wouldn't move much anymore. But that's a lot of ifs that I'm not sure about.

starcanuck64
2012-Sep-14, 01:28 AM
Normal plate movement is more due to the slow convection of the mantle I think, from what I recall about super continents, they create the heat that eventually breaks them apart by insulating the mantle underneath them.

It could be that mantle convection is more limited near the poles, time to do a little reading up.

tnjrp
2012-Sep-14, 04:52 AM
They don't make it clear what kind of flora they found other than relating it to seasonal rainfallWithout knowing that either, I was assuming they would've been temperate rainforests dominated by coniferous trees, somewhat similar to seasonal rain forest zones of the the Pacific Northwest Coast of North America.

Looks like they were more @ what is found in New Zealand tho.

The Baobab (type) trees should work well in conditions were it's dark for long periods of time and then lots of rainfall for a while.

ravens_cry
2012-Sep-14, 06:14 AM
Dammit, where's my time machine?!:think:

Romanus
2012-Sep-16, 03:20 AM
I'm guessing Antarctic beech was probably a fairly common component; it's a cold-tolerant but temperate species limited to Australia and southernmost South America today.

By the by, Scotese.com has much better paleomaps: http://www.scotese.com/earth.htm

Rhaedas
2012-Sep-16, 06:08 PM
Normal plate movement is more due to the slow convection of the mantle I think, from what I recall about super continents, they create the heat that eventually breaks them apart by insulating the mantle underneath them.

It could be that mantle convection is more limited near the poles, time to do a little reading up.

That's sort of what I was trying to describe.

For what it's worth, if you go back to the Percambrian, 650 Mya, Antarctica WAS on the Equator. But that predated land life.

starcanuck64
2012-Sep-17, 05:15 PM
That's sort of what I was trying to describe.

For what it's worth, if you go back to the Percambrian, 650 Mya, Antarctica WAS on the Equator. But that predated land life.

It's amazing how dynamic the Earth's surface is over long enough periods of time.

http://geomaps.wr.usgs.gov/parks/pltec/scplseqai.html

Githyanki
2012-Sep-24, 06:20 PM
IIRC, yes, very depressing. Been stuck down there near the pole for a long time. Wonder if any dinosaurs there survived the KT extinction?

Sometimes I wonder that since the dinosaurs are used to extended periods of no sunlight, they were able to hibernate during the KT and survived until 15MYA when Antarctica fully froze.

Ivan Viehoff
2012-Sep-26, 12:52 PM
Without knowing that either, I was assuming they would've been temperate rainforests dominated by coniferous trees, somewhat similar to seasonal rain forest zones of the the Pacific Northwest Coast of North America.

Looks like they were more @ what is found in New Zealand tho.
Or Chile. The idea that temperate rain forests are dominated by coniferous trees is a strictly northern hemisphere perspective. Though even in the northern hemisphere, birches and willows grow to the north of the conifers.

Fossils of southern beech have been found in Antartica from rather more recent periods than 40mya.