Earth & Environment - Posted by Gary Galluzzo-Iowa on Monday, February 15, 2010 12:18 - 2 Comments 
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(2 votes, average: 5.00 out of 5) Loading ...Shifting debate on sea level models
A caver explores speleothem encrustations, a type of mineral deposit, in a coastal cave on the Mediterranean island of Mallorca. Researchers studying the deposits have found evidence that sea level was about one meter above present-day levels around 81,000 years ago, a time preceded by rapid ice melting, on the order of 20 meters of sea level change per thousand years. (Credit: Tony Merino)
U. IOWA (US)—New findings about the close link between changes in sea level and Earth’s climate challenge theories about the rates of ice accumulation and melting during the Quaternary Period—the time interval ranging from 2.6 million years ago to the present.
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Jeffrey Dorale, assistant professor of geoscience at the University of Iowa, and colleagues collected data on speleothem encrustations, a type of mineral deposit, in coastal caves on the Mediterranean island of Mallorca and found that sea level was about one meter above present-day levels around 81,000 years ago.
The research challenges other studies that indicate sea level was as low as 30 meters—the ice equivalent of four Greenland ice sheets—below present-day levels. Their findings are reported in the journal Science.
Dorale says the sea level high stand of 81,000 years ago was preceded by rapid ice melting, on the order of 20 meters of sea level change per thousand years and the sea level drop following the high water mark, accompanied by ice formation, was equally rapid.
“Twenty meters per thousand years equates to one meter of sea level change in a 50-year period,” Dorale says. “Today, over one-third of the world’s population lives within 60 miles of the coastline. Many of these areas are low-lying and would be significantly altered—devastated—by a meter of sea level rise. Our findings demonstrate that changes of this magnitude can happen naturally on the timescale of a human lifetime. Sea level change is a very big deal.”
Dorale also notes that although their findings disagree with some sea level estimates, such as those from Barbados and New Guinea that come from ancient coral reefs, they are in agreement with data gathered from other sites such as the Bahamas, the U.S. Atlantic coastal plain, Bermuda, the Cayman Islands, and California.
“There has been a long-standing debate on this issue, but our data is pretty robust,” he says. “The key to our research is two-fold. First, the speleothem approach we employed is novel and extremely precise compared to other methods of sea-level reconstruction. Second, Mallorca appears to be particularly well suited to the task, because neither tectonics nor isostasy—geological forces of crustal motion—over-complicate the record. It’s really close to the ideal scenario. It’s also a heck of a nice place to do fieldwork.”
Researchers from the University of Iowa, University of South Florida, Tampa; Universitat de les Illes Balears, Mallorca, Spain; and University of Rome III, Italy contributed to the work, which was supported by the National Science Foundation.
University of Iowa news: http://news.uiowa.edu/
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2 Comments
Sea Levels are falling and have been doing so for perhaps millions of years. Your guess is as good as mine in that conjecture. Where there is no debate is the receding seas. I can prove substantially that seas have been receding over thousands of years since recorded history. We only have to look at all ancient civilizations and see how they evolved: more importantly where they evolved. All ancients evolved in the high regions of the earth and came downward as the seas receded. Read my latest book entitled ” The Ascent of Man: Downhill all the Way” see http://www.widemargin2000.com to get your copy. You can also see my Articles on Google under “The Mysterious Receding Seas” . You can view my videos on http://www.youtube.com. Richard Guy: Tel; 575-740-1084.
Sea levels are not rising nor are they going to rise if and when the ice caps melt totally and they wont. The argument is much overated and over sold. It creates more debate than substance. The seas are receding, all 170 of them, and some are disappearing. Sea level has been falling globally with a few exceptions where the land level is falling instead. This land slump is due to tectonics. This tectonic slump of land is an expression of the same phenomenon that makes sea levels fall globally. That however is part of a more complex explanation which is unnecesary unles you can first grasp the basic concept of Earth Expansion. Suffice it to say at this juncture that our Earth is Expanding and as it expands the sea levels fall. I will go no further here to reveal the wonderful dicoveries that await those who can overcome the outdated mindset of a static earth and move on to overturn Isostatic or Post Glacial Rebound. A new age of dicovery awaits if only we could overlook the media hype and the false prognotications and hypotheses such as rising sea levels. New Wonders await.