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

Volvo Ocean Race 2014-15 CEO Knut Frostad talks (Part I) *Feature by Rob Kothe and the Sail-World team,










Maxi yacht rendezvous this September in Sardinia by International Maxi Association,


















America's Cup: Team NZ wish Davis well with new team by Richard Gladwell, Sail-world.com/nz,


Fisher's View: Sailing perfection at Hamilton Island- Day 3 by Bob Fisher, Hamilton Island, Queensland




2014 Formula Kite World Championship Day 1 by Markus Schwendtner, Istanbul
























Opera House Cup - Images by Ingrid Abery by Ingrid Abery/Sail-World.com,


Teams descend upon Cowes for inaugural J/111 World Championships by Stuart Johnstone, Cowes, Isle of Wight, England






Sopot Match Race - Poland's Tour debut deemed a triumph
Vineyard Race celebrates 80th running of the East Coast classic
Nanjing Youth Olympic Games: Young sailors begin racing on Lake Jinniu
AWT Quatro Desert Showdown - Victory for Morgan Noireaux
Sevenstar Round Britain and Ireland Race - Day 8: Test of endurance
Bart's Bash: Over 2300 entered from 588 yacht clubs - Join here
Halifax ready to welcome the world at 2014 IFDS World Championships
RC44 World Championship title to Bronenosec + Video
Audi Hamilton Island Race Week: Day 2 Images by Crosbie Lorimer
IFDS Worlds - Gary Jobson to attend opening ceremonies
Melges 32 U.S. National Championship - Dalton DeVos crowned champion
2014 Nanjing Youth Olympic Games trailer
2014 Chicago Grand Slam - Canfield wins
Round Britain and Ireland Race - Varuna takes overall lead
Audi Hamilton Island Race Week; Crosbie Lorimer Day 1 Images
Fisher's View: Hamilton Island Race Week - Day 1 - Stayin' Alive
CORK Olympic Classes Regatta 2014 - Day one
Youth Olympics: practice over, athletes welcomed, time for YOG sailing
Round Britain and Ireland Race - Record for Artemis-Team Endeavour
2014 Melges 32 U.S. National Championship - Day 2
Sevenstar Round Britain and Ireland: Artemis sets fourth course record   
2014 Chicago Grand Slam - Top seeds survive as semi-finalists   
420 and 470 Junior Europeans - Breezy day 4 in Gdynia   
RC44 World Championship - Dramatic improvement for Artemis Racing   
18' Skiff International Regatta - Action begins August 25th   
Round Britain and Ireland Race - Challenging conditions arise   
Round Britain and Ireland Race - Record-breaking monohull victory   
Round Britain and Ireland Race - Dongfeng Race Team finishes third   
RC44 Marstrand World Championship - Bronenosec the star performer   
Bahamian Olympic Sailor to carry flag in honour of Sir Durward Knowles   
Sevenstar Round Britain and Ireland Race: Records continue to tumble   
Sevenstar Round Britain and Ireland Race: Course Record for Team SCA   
Round Britain and Ireland Race - Team Alvimedica completes the race   
2014 Melges 32 U.S. National Championship - Day 1   
420 and 470 Junior European Championships - A crazy race day 3   
2014 Sevenstar Round Britain and Ireland Race: Monohull record smashed   
2014 Chicago Grand Slam - Top seeds take the early lead   
Frostad proud to have seven Volvo Ocean Race boats with seven sponsors *Feature   
RC44 World Championship - Bronenosec Sailing Team on form   
Round Britain and Ireland Race - Dongfeng defends third position   


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