Naked Science Forum
Life Sciences => The Environment => Topic started by: Geezer on 28/03/2010 21:43:53
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According to SciAm, in a paper published in Feb 12 Science some researchers have discovered some really unexpected changes in historical global sea levels.
They studied speleotherms in caves in Mallorca to make their determinations. Two of their interesting (if not downright scary) conclusions:
Sea levels were one meter higher (yes! higher) 81,000 years ago than present day levels. (That's really weird, because previous studies say they would have been as much as 30 meters lower because of all the ice locked up on land.)
Sea levels have changed up or down at rates as high as two meters in a century. This is much faster than previous data indicated.
One of the authors is a Jeffery Dorale, University of Iowa.
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Totally plausible
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Are they suggesting that global sea levels were higher than previously thought i.e. there was much more surface water? That wouldn't make much sense to me, and the fact that plenty of submerged prehistoric settlements have been found show that sea levels have certainly been lower than they are now.
What seems more likely, and more plausible to me, is that the land may have risen or fallen in different regions, just as much of the northern hemisphere is in isostatic rebound from the ice sheets of the last ice age. Of course, I don't think the ice sheets got as far south as Mallorca in the last ice age, but there are other isostatic factors too, that might result the land moving up or down.
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Geezer,
After a bit of googling it seems to me Sea Level changes are continuous, and bit mystifying. Here is an additional study on Mediterainean changes over the last 2,500 years:
"During the Hellenistic period, the sea level was about 1.6 meters lower than its present level; during the Roman era the level was almost similar to today's; the level began to drop again during the ancient Muslim period, and continued dropping to reach the same level as it was during the Crusader period; but within about 500 years it rose again, and reached some 25 centimeters lower than today's level at the beginning of the 18th century." http://www.eurekalert.org/pub_releases/2010-01/uoh-tsl012610.php
One might expect sea levels to be lower during the cooler pre and post Roman Eras due to more ice. However, the levels are reported to have continued to fall despite subsequent Midieval Warming, then rose again during The Little Ice Age. Weird. Its another cautionary tale about jumping to conclusions based on clearly incomplete understanding.
Incidentally, even extensive dam building can lower Sea Levels. Someplace I read the mid 20th century flury of such activity might have lowered sea levels by as much as 10 cm.
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Well, it all does seem a bit strange, but the science seems to be quite reputable. Beats me! That's why I posted the info.
In the article they do say that Mallorca is very stable. Maybe there was an ice dam at the Straits of Gibraltar [;D] [::)]
Wasn't there a waterfall there at one time - although I think it was flowing in, not out!
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I am part of a research group that does work developing speleothems as a proxy...Id like to ask them about the authors and what they think of the paper. We just had our weekly meeting, but Ill bring it up next Monday.
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I am part of a research group that does work developing speleothems as a proxy...Id like to ask them about the authors and what they think of the paper. We just had our weekly meeting, but Ill bring it up next Monday.
That would be great! Thanks Frethack.
(You might have to go to Mallorca to check it out for yourself.)