Please select your home edition
Edition
Newport Boat Show 728x90

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

by Woods Hole Oceanographic Institution on 21 Sep 2011
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.


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.'


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.


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.

Wildwind 2016 660x82Bakewell-White Yacht DesignNewport Boat Show 2016 660x82

Related Articles

WHO statement on Zika virus
The third meeting of the EC convened by the Director-General under IHR 2005 regarding microcephaly and Zika virus The third meeting of the Emergency Committee (EC) convened by the Director-General under the International Health Regulations (2005) (IHR 2005) regarding microcephaly, other neurological disorders and Zika virus was held by teleconference on 14 June 2016, from 13:00 to 17:15 Central European Time.
Posted on 16 Jun
Atlantic Cup 2016 - a race with an environmental commitment
The Atlantic Cup continues to further its mission for the 2016 race by examining the global economic impact of the ocean The Atlantic Cup continues to further its mission for the 2016 race by examining the global economic impact of the ocean and how an unhealthy ocean can affect the economy.
Posted on 7 Apr
Zika virus situation report
From 1 January 2007 to 16 March 2016, Zika virus transmission was documented in a total of 59 countries and territories. From 1 January 2007 to 16 March 2016, Zika virus transmission was documented in a total of 59 countries and territories. Cuba and Dominica are the latest to report autochthonous (local) transmission of Zika virus on 14 and 15 March, respectively. Five of these countries and territories reported a Zika virus outbreak that is now over.
Posted on 2 Apr
Have Norway scientists solved the Bermuda Triangle mystery?
The Bermuda Triangle has been said to have claimed numerous ships and aircraft over the years The Bermuda Triangle has been said to have claimed numerous ships and aircraft over the years, and everything from aliens to remnants from the lost island of Atlantis have been fingered as the culprits.
Posted on 15 Mar
Cyclone Winston Relief Fund – Help the people of Fiji
Sea Mercy is sending volunteer fleet of small and large vessels, loaded with shelter, food and medical supplies to Fiji. Sea Mercy is once again sending our volunteer fleet of small and large vessels, loaded with shelter, food, water and medical supplies and teams to Fiji.
Posted on 27 Feb
Flying Scot Atlantic Coast Champs - Hanson Medals awarded for rescues
US Sailing Safety at Sea Committee awarded the Arthur B. Hanson Rescue Medals to eight boats for their heroic efforts The US Sailing Safety at Sea Committee awarded the Arthur B. Hanson Rescue Medals to eight boats for their heroic efforts when a microburst storm hit the 2015 Flying Scot Atlantic Coast Championship, hosted by the Blackbeard Sailing Club, in New Bern, NC on September 12.
Posted on 2 Feb
Eco-warriors Sea-Bin crowd sharing critical stage with nine days to go
The automated marina cleaning SeaBin project has raised 86% of their target with 9 days left. The automated marina cleaning SeaBin project has raised $198,020 of $230,000.00 with nine days left on their Indiegogo crowdfunding platform, but they need more help now.
Posted on 29 Dec 2015
Higher levels of Fukushima Cesium detected offshore
Scientists monitoring the spread of radiation in the ocean from the Fukushima nuclear accident report Scientists monitoring the spread of radiation in the ocean from the Fukushima nuclear accident report finding an increased number of sites off the US West Coast showing signs of contamination from Fukushima. This includes the highest detected level to date from a sample collected about 1,600 miles west of San Francisco.
Posted on 6 Dec 2015
Don’t be a Tosser – Not your usual environmental article!!
The word ‘Tosser’ in the Oxford English dictionary means – ‘a person or thing that throws something’. The word ‘Tosser’ in the Oxford English dictionary means – ‘a person or thing that throws something’. There is no need for me to tell you the other meaning that is commonly used around the world. However in this article it will refer to both at the same time as someone who tosses trash into the ocean, truly is a tosser.
Posted on 3 Dec 2015
Warming ocean worsened Australia’s fatal 2010/2011 floods
Researchers shows that warming of Indian and Pacific oceans played a role in increasing the risk of floods in 2010/2011 A study by a team of U.S. and Australian researchers shows that long-term warming of the Indian and Pacific oceans played an important role in increasing the risk of the kind of devastating floods that struck Australia in 2010/2011.
Posted on 21 Nov 2015