Models of sea level change during ice-age cycles challenged

Washington, Feb 12 (ANI): A new research has challenged 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.

According to Jeffrey Dorale, assistant professor of geoscience in the UI (University of Iowa) College of Liberal Arts and Sciences, global sea level and Earth's climate are closely linked.

Data he and colleagues collected on speleothem encrustations, 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 that 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," he said.

"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," he added.

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 US 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," said Dorale.

"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 o the ideal scenario," he added. (ANI)