sail-world.com
 
 
News Home Cruising Photo Gallery Video Gallery

 

Sail-World.com : Possible future sea-level changes hinted by new coral dating methods

Possible future sea-level changes hinted by new coral dating methods

'WHOI geochronologist William G. Thompson, lead author of the study, sampling a fossil coral on Great Inagua Island, Bahamas in 2006.'    © H. A. Curran, Smith College

New evidence of sea-level oscillations during a warm period that started about 125,000 years ago raises the possibility of a similar scenario if the planet continues its more recent warming trend, says a research team led by the Woods Hole Oceanographic Institution (WHOI).

In a paper published online in the Sept. 11 Nature Geoscience, the researchers report data from an improved method of dating fossil coral reef skeletons in the Bahamas. By calculating more accurate ages for the coral samples than previously possible, they found that sea levels were considerably less stable than earlier believed--oscillating up and down by four to six meters (13-20 feet) over a few thousand years about 120,000 years ago during a period known as the Last Interglacial.

'This was the last time that climate was as warm as—or warmer than—today,' said WHOI geochronologist William G. Thompson, lead author of the study. 'If today’s ice sheets continue to melt, we may be headed for a period of ice sheet and sea-level change that is more dynamic than current observations of ice sheets suggest.'

The polar ice caps currently are shrinking and sea level is rising at a rate of about 30 centimeters (one foot) per century. 'How much sea level will rise over the next century or two is a crucial question for the significant part of the world’s population that lives in coastal zones,' Thompson said.

Researchers sampled and dated corals from two fossil reefs of different ages on the islands of Great Inagua and San Salvador, in the Bahamas. This photo shows a large individual fossil coral from the younger reef, which grew directly on the remains of an older generation of similar corals. The two reefs are separated by a wave-cut surface, also visible in the photo, which was eroded in the swash zone after sea level fell. Since both generations of corals grew in about 3 m of water, and the wave- -  © H. A. Curran, Smith College  

A better understanding of sea-level change in the past can help to inform predictions for the future. Historical records such as those from tide gauges extend back only a century or so. 'The geological record offers a longer perspective on rates of change,' Thompson said, 'and sea-level changes during previous warm intervals are especially relevant to today’s situation.' Sea levels during the Last Interglacial are known to have been about six meters (20 feet) higher, on average, than they are today. 'The real surprise is that sea levels were oscillating during this period.'

To get more accurate age estimates from the geological record, Thompson developed an advanced way of interpreting the uranium and thorium isotope ratios that have been traditionally used as a coral dating method. Until now, scientists attempting to date Last Interglacial coral reefs concluded erroneously that sea level was relatively stable during this period. 'Our analysis of Last Interglacial fossil reef ages represents a breakthrough in our understanding of U-Th coral dating, leading to improved chronologies of past sea-level change,' Thompson said.

Thompson teamed up with colleagues H. Allen Curran and Brian White of Smith College, and Mark A. Wilson of the College of Wooster, experts on the key Bahamas fossil coral sites. 'The geologic evidence for sea-level change at these sites is convincing,' said Curran, 'but we couldn’t absolutely prove sea-level oscillation without more precise dating.'

A fossil coral like those the authors sampled and dated to reconstruct sea level changes during the Last Interglacial period. -  © H. A. Curran, Smith College  

Because coral reefs grow near the sea surface, they are accurate markers of former sea levels. Two fossil reefs are evident at the Bahamas sites, separated by an erosional surface that was cut by wave action. The first reef grew when sea levels were about four meters (13 feet) higher than today. 'The fall of sea-level is indicated by the wave-cut erosion of this first reef,' said Wilson, 'and the second sea-level rise was recorded by the growth of new corals on this eroded surface. The dating of fossil corals below and above this erosional surface, using our new methods, reveals important details about the timing of sea-level change that were previously obscured.'

The finding of a significant sea-level oscillation 120,000 years ago is in sharp contrast to the last 5,000 years, where sea level has been relatively stable. 'It appears that the smaller ice sheets of the Last Interglacial were significantly less stable than today’s ice sheets,' Thompson said.

Researchers at the site of two fossil reefs described in the new study. In background, from left, William Thompson of WHOI, Mark Wilson of the College of Wooster, and undergraduate students Ann Steward and Emily Griffin from the College of Wooster. -  © H. A. Curran, Smith College  

Should the current warming trend continue, Thompson said, a scenario similar to that of the Last Interglacial could result. 'Variable sea level during the last Interglacial points to instability in the polar ice sheets, which were somewhat smaller than today. If changing climate leads to smaller ice sheets in the future, this may provoke similar instability.' The work was supported by the WHOI Ocean and Climate Change Institute, the Comer Science and Education Foundation, and the National Science Foundation.

Woods Hole Oceanographic Institution website

The Woods Hole Oceanographic Institution is a private, independent organization in Falmouth, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the ocean and its interaction with the Earth as a whole, and to communicate a basic understanding of the ocean's role in the changing global environment.




by Woods Hole Oceanographic Institution

  

Click on the FB Like link to post this story to your FB wall

http://www.sail-world.com/index.cfm?nid=88732

9:41 PM Tue 20 Sep 2011 GMT






Click here for printer friendly version
Click here to send us feedback or comments about this story.


News - USA and the World





















Big Boat Series - It's not the size, it's the length by Erik Simonson, Pressure-Drop.US,




















470 Men and Women Worlds - Champs take over leaderboard by 470 International Association Class,


























J/24 World Championship - Excitement builds for Newport racing
Volvo Ocean Race - Seb Marsset joins Team Alvimedica
Fall Seamanship training opportunities at New York Yacht Club
Rolex Big Boat Series: More images from San Francisco - Final Day
AWT Hatteras Wave Jam action commences on day 3
Rolex Big Boat Series: Images from San Francisco - Final Day
ISAF Sailing World Championships - Watch medal races live here
Hobie 16 Open North American Championships and Pan Am Games qualifier
ISAF Sailing World Championship - Videos from Santander
ISAF Sailing Worlds: Buckingham into Medal Race, 470's stay consistent
470 Men and Women Worlds - Vadlau and Ogar into pole position
2014 Chicago Match Cup - Defending champion on top
ISAF Sailing Worlds, Santander - Strong competition for RS:X fleets
ISAF Sailing Worlds, Santander - Big breeze on day 6 + Video
ISAF Sailing Worlds, Santander - Buckingham into Laser Medal Race
U.S. Multihull Championship - Hobie Alter Trophy to be decided
ISAF Sailing Worlds - The kind of form most sailors only dream about
Royal Cup Marina Ibiza - Quantum Racing ahead of target
ISAF Worlds Santander - 19 Rio 2016 Laser Radial spots awarded
Santander 2014 ISAF Worlds - 21 broadcasters to take live coverage
Rolex Swan Cup - Looking forward to the next 30 years   
America’s Cup: The Future is foiling – AC45s to be modified   
Volvo Ocean Race: Win a stopover trip by designing an ECsix T-Shirt   
Red Bull 49erFX: On the eve of the Worlds in Santander   
America's Cup: Ben Ainslie Racing launches partnership with Yamaha   
2014 Chicago Match Cup - Starts tomorrow   
Rio 2016 Daylight the issue for Olympic sailing regatta   
ISAF Sailing World Championships - USA 470's and Lasers battle at top   
ISAF Sailing World Championships - Santander - Day 5 video highlights   
ISAF Sailing World Championships - Santander images by Jesús Renedo   
PWA Cold Hawaii World Cup - No action on day 2   
470 Men and Women Worlds - Game on for Olympic Qualification   
ISAF Sailing World Championships: Finns off to slow start in Santander   
ISAF Sailing World Championships - Seesaw Day 5 in Santander + Video   
ISAF Sailing World Championships - 470 sailors shine in Santander   
Royal Cup Marina Ibiza - Kiwi Ray Davies returns to TP52 fleet   
Starboard Hatteras Wave Jam - No windsurfing action on day 1   
A complete recap of the most successful Melges 20 World Championship   
Rolex Big Boat Series - Prizegiving images by Chuck Lantz   
ISAF Santander - Upwards path for Austrian women's 470 crew + video   


For this week's complete news stories select    Last 7 Days
   Search All News
For last month's complete news stories select    Last 30 Days
   Archive News







Sail-World.com  


















Switch Default Region to:

Social Media

Asia

Australia

Canada

Europe

New Zealand

United Kingdom


http://www.sail-world.com/event_images/image/Twitter_logo_small.png http://www.sail-world.com/event_images/image/FaceBook-icon.png  http://www.sail-world.com/event_images/image/RSS-Icon.png

United States

Cruising Northern

Cruising Southern

MarineBusiness World

PowerBoat World

FishingBoating World

 

Contact

Commercial

News

Search

Contact Us

Advertisers Information

Submit news/events

Search Stories/Text

Feedback

Advertisers Directory

Newsletter Archive

Photo Gallery

 

Banner Advertising Details

Newsletter Subscribe

Video Gallery

Policies

 

 

 

Privacy Policy

 

 


Cookie Policy

 

 



This site and its contents are © Copyright TetraMedia and/or the original author, photographer etc. All Rights Reserved.  Photographs are copyright by law.  If you wish to use or buy a photograph contact the photographer directly.
XLXL NEW US
LocalAds   DE  ES  FR  IT