Powerboat-World.com
 
 
News Home Video Gallery Newsletters FishingBoating Features Photo Gallery Sail-World Australia Australian Cruising
Sail-World Australia Australian Cruising MarineBusiness-World

 

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.powerboat-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.


Power Boat News







Abbot Point onshore disposal by Great Barrier Reef Marine Park Authority,










Great Barrier Reef plan released for comment by Queensland Minister for Environment,










Brisbane Boat Show begins *Feature by Jeni Bone,








































Court judgement a stark reminder about towing safety
Australian Offshore Superboat 2014 - Superboats ready for Redcliffe
Southport Yacht Club’s annual Sail Past and Blessing of Fleet Ceremony
Gosport Grand Prix of the Sea finale to decide P1 champions
Camper & Nicholsons Yachts presents the Sagitta 42
GT15 and GT30 European Championships - Jelf takes to the podium twice
Marine Rescue crew saves cruiser in trouble in rough conditions
XCAT Series gets set to conquer another continent in 2015
Dangerous conditions for boaters on most of NSW coast
2014 Mandurah Boat Show - Third largest boat show in Australia
2014 Gold Coast International Marine Expo - Eye on the big picture
Mediterranean Grand Prix - Powerboat racing heavyweights head to Ibiza
Mediterranean Grand Prix - World Aquabike stars all set
Antarctic sea-level rising faster than global rate
Powerboat champions gear up for Honda RYA Youth RIB National final
Andrew Scott joins Superior as General Manager *Feature
2014 Gold Coast International Marine Expo - Fastest Jet Ski ever built
Best Birthday Party ever at Southport Yacht Club! *Feature
‘Hall of Fame’ status for Empire Marina *Feature
Girl power all set for Nottingham powerboat racing action
Cowes to Torquay Race 2014 - Intense activity in preparation   
Fort Lauderdale International Boat Show - 13 things to See and do   
Australian Offshore Superboat Champ - 15 Superboats in Coffs Harbour   
European première for Belize 54 Daybridge at Cannes Yachting Festival   
‘Fish Friendly’ accreditation for Sanctuary Cove Marina   
Plethora of Powerboat racing action this weekend   
Vicsail Boat show Open Day at Rushcutters Bay   
Marine15 - prospectus available online now + VIDEO *Feature   
Southport Yacht Club achieves Clean Marina certification + VIDEO *Feature   
Port Kembla Volunteers bring in 75 metre monster from 5nm offshore   
Gold Coast Int'l Marine Expo - Make every moment one to remember   
Dangerous conditions for boaters from Queensland border to Sydney   
4x4 Outdoors Show and Fishing and Boating Expo - Busy opening day   
Summerland 40 LR named Boat of the Year   
More new boats brand Brisbane Boat Show as a spectacular showcase   
Xiamen Int'l Boat Show 2014 moving to a new home   
Yamaha inspires students to succeed   
NSW EPA supports Marina Industry Environmental Accreditation   
Powerful Yanmar 12AY Diesel Series revealed   
Buy a slice of Solar Sailor history *Feature   


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/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 WAS PBW
LocalAds   DE  ES  FR  IT