The Arctic's Tropical Past

140Mandak262Jamuna writes "The BBC reports on findings that the arctic/polar region was tropical some 55 Million years ago." From the article: "Although the data tells us how the world changed from one with green house conditions to one with ice house conditions millions of years ago, it may also help scientists to predict what will result from the present changes in climate. Appy Sluijs points out that the data reveals that some of the climate models used to detail the Arctic's history got things wrong, and as they are the same models that predict our future climate they may need adjusting. " The reader pointed out that this may have had as much to do with continental drift as it did climate change.

Comments

Not continental drift

[uncleO]

Continental drift occurs much too slowly to have the effects indicated by the core samples in this study. Over the last 55 million years, the arctic has been about where it is now.

Also, it is ridiculous to suppose that the region moved towards and away from the pole to match the wild temperature fluctuations revealed in the data.

Some of the other speculation I have read on this story is also suspect to me. Namely, trees ringing the Arctic Ocean. I find it difficult to believe that trees would flourish with long periods of darkness annually. But I could be wrong here; there are some plants native to the region today--but they are dormant for most of the year.

Re:Not continental drift

[Red Flayer]

"I find it difficult to believe that trees would flourish with long periods of darkness annually."

Why is that? Deciduous trees in temperate areas now thrive without photosynthesis for many months each year. I'd even speculate that extremely northern (or southern) origin of deciduous trees helps explain their seasonal metabolic extremes -- whereas coniferous trees probably evolved an a latitude with less seasonal variation (and less moisture).

Re:Not continental drift

[spun]

From the wikipedia article on continental drift: "South America and Africa are moving apart at an average of 5.7 cm per year, due to the seafloor spreading along the Mid-Atlantic Ridge. This is comparable to the growth speed of a fingernail. The fastest recorded seafloor spreading takes place along the East Pacific Rise at 17.2 cm per year"

Using the lower number gives us a distance of 2850 kilometers in 50 million years. Not quite far enough for major climate change just based on distance. However, this amount of drift could severely alter the Atlantic Conveyor, a heat pump that moves tremendous amounts of heat from the equator to the poles. It is also enough distance to affect the amount of light available to trees.

It should also be noted that using the higher figure would result in a movement of 8600 kilometers, nearly the distance from the equator to the poles.

Re:Not continental drift

[tdemark]

Using the lower number gives us a distance of 2850 kilometers in 50 million years.

You mean the lower number that is the relative speed between two plates that are moving away from each other?

Read what you posted again:

South America and Africa are moving apart at an average of 5.7 cm per year

The implication is that South America is moving 2.85 cm west each year and Africa is moving 2.85 cm east each year.

Since you are dealing with the absolute speed of a single plate (not its relative speed to another), you could "get away" with 2.85 cm per year.

However, since we are talking about either North American plate or the Eurasian plate, you should use 1.15 cm/year or 0.95 cm/year. This would be a worst case of around 600 km.

- Tony

Re:trees grow in soil

[MrFebtober]

The northernmost parts of Canada, Russia, and Alaska, as well as all of Greenland are considered to represent the Arctic Region of the Earth. The Geographical pole itself is just ice, but there is plenty of Arctic Tundra up there.