Research challenges models of sea level change during ice-age cycles (1 meter change in 50 years)

[OKIsItJustMe]

http://news-releases.uiowa.edu/2010/february/021110dorale.html

University of Iowa News Release

Embargoed for 2 p.m. ET Feb. 11, 2010

Research challenges models of sea level change during ice-age cycles

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 -- may need to be revised, thanks to research findings published by a University of Iowa researcher and his colleagues in the Feb. 12 issue of the journal Science.

Jeffrey Dorale, assistant professor of geoscience in the UI College of Liberal Arts and Sciences, writes that global sea level and Earth's climate are closely linked. Data he and colleagues collected on speleothem encrustations (see photo right), a type of mineral deposit, in coastal caves on the Mediterranean island of Mallorca indicate that sea level was about one meter above present-day levels around 81,000 years ago. The finding challenges other data that indicate sea level was as low as 30 meters -- the ice equivalent of four Greenland ice sheets -- below present-day levels.

He said 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 said. "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 noted 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 said. "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."

Dorale's colleagues include Bogdan Onac of the University of South Florida, Tampa; Joan Fornos, Joaquin Gines and Angel Gines, all of the Universitat de les Illes Balears, Mallorca, Spain; Paola Tuccimei of the University of Rome III, Italy; and UI associate professor of geoscience David Peate.

The research was supported by the National Science Foundation in a grant to Dorale and Onac.

STORY SOURCE: University of Iowa News Services, 300 Plaza Centre One, Iowa City, Iowa 52242-2500
MEDIA CONTACT: Gary Galluzzo, writer, 319-384-0009, [e-mail]

[Viking12]

1. Rec

Not because the article is all that important or original but, rather, to offset the denier douchebag unrec :evilgrin:

[OKIsItJustMe]

2. TIME Magazine - Glaciers: Changing at a Less Than Glacial Pace

http://www.time.com/time/health/article/0,8599,1963878,00.html

Glaciers: Changing at a Less Than Glacial Pace

By Bryan Walsh Thursday, Feb. 11, 2010

Glaciers are thought to change at, well, a glacial pace. Certainly that has been true throughout the planet's history. The current ice age — known as the Pilocene-Quatenary glaciation, which began 2.6 million years ago — has witnessed some 20 cycles of glacial (freezing) and interglacial (thawing) periods, with ice sheets advancing and retreating completely on roughly 100,000-year time scales. But scientists are unsure exactly what prompts the shifts in cycles.

In glacial periods, vast ice sheets cover much of the planet, and sea levels are as much as 130 meters lower than they are today (all that extra water is locked up in ice). During interglacial periods — we are enjoying one now, East Coast blizzards notwithstanding — the ice sheets retreat, the glaciers melt and sea level rises. The expansive but quickly melting ice sheets of Greenland, the North Pole and Antarctica are all that is left of our last glacial period, which reached its peak about 20,000 years ago.

Now a new study published in the Feb. 12 issue of Science indicates that the balance of the world's ice may be shifting faster than scientists thought, which may have consequences in a warming world. A team of scientists traveled to the Spanish island of Mallorca, where they visited a coastal cave that has been submerged off and on by the Mediterranean Sea for hundreds of thousand of years, as glacial periods have waxed and waned. They dated the layers of the mineral calcite, which were deposited by the seawater in rings on the cave walls, as on a bathtub.

Scientists were then able to infer the approximate sea level at the time the calcite was deposited, and estimate that some 81,000 years ago sea levels were about 1 m higher than they are now — which suggests that global temperatures were at least as high, or higher than they are now, even though CO2 concentrations in the atmosphere were much lower then. The study also indicates that the sea level was changing rapidly around this time period, rising as much as 1 m the century before, as ice melted, and then falling afterward at around the same speed, as ice began to freeze once more. Rather than forming steadily and melting steadily, the process of glacier freezing and receding may be more more unstable, reflected in sudden rising and falling of the sea level. "It's fair to say that this means glaciers may change somewhat faster than we once inferred," says Jeffrey Dorale, a geoscientist at the University of Iowa and the lead author of the Science paper. "It does suggest there can be very fast is melting and very fast ice building at times when CO2 levels were lower than now."

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