Featured Research

from universities, journals, and other organizations

Can Ancient Rocks Yield Clues About Catastrophes Like Hurricane Katrina?

September 8, 2005
University of Newcastle upon Tyne
Scientists studying sediments laid down on the ocean floor during greenhouse conditions 85 million years ago have gained insights into the causes and mechanisms of climate change, which many people believe is the root cause of recent natural catastrophes including Hurricane Katrina.

An oxygen-free ocean from bottom to surface is probably the worstscenario that marine higher life can experience. Are processes andfeedbacks linking the atmosphere to the deep ocean capable to cause arapid change from an oxygen-rich to an oxygen-free deep ocean? And whatare the consequences for the global carbon cycle that ultimately drivemarine and terrestrial ecosystems and climate variation?

Related Articles

These are fundamental and burning questions on the society's agenda.Hurricane Katrina and other natural catastrophes in recent years haveshown how vulnerable mankind is in the face of nature. Professor TomWagner of Newcastle University, England, led a cross-disciplinary studyof geological records combined with climate modeling to shed new lighton the mechanisms and processes that led to repetitive rapid climaticchange with major impact on the ocean during past greenhouseconditions.

By analysing sediments laid down on the ocean floor about 85myears ago in the Cretaceous, the research team found evidence thatCretaceous greenhouse climate was highly variable and repeatedlyresulted in major changes in ocean chemistry and deep circulationcausing disastrous consequences for marine ecosystems. These extremeconditions fostered massive burial of dead organic matter from marinespecies, such as algae and plankton, at the sea floor, leading to theformation of distinct sediments, "marine black shale", also well knownas the world's primary source for oil and gas.

Professor Wagner and colleagues uncovered evidence of themechanisms that drove rapid and repetitive climate change by studyingthe quantity and content of proxy parameters in black shale in a coreof sedimentary rock drilled out of the ocean bed, off Africa's IvoryCoast, and comparing these results with data from a global climatemodel.

The model data were used to quantify the freshwater run-offfrom tropical Africa into the equatorial Atlantic, where the core hasbeen drilled, and to specify the role of orbital configuration and thewater cycle on climate and oceanographic variation. With these data, itwas possible to explain the formation of the sedimentary succession ofblack shale and carbonate-rich sediments, indicating alternationbetween oxygen-depleted and oxygen-rich conditions in the deep ocean.All life other than simple organisms like bacteria would have beenseriously depleted in the deeper ocean as oxygen became progressivelyscarce. On land, the climate variability would cause strong regionalcontrasts, with widespread deserts at mid-latitudes and extremely humidareas in the tropics.

Processes in the atmosphere driven by cyclic changes in theamount of energy from the sun entering the top of the atmosphere(insolation) have been identified to be the cause for the observeddramatic changes in ocean chemistry that resulted in the formation ofblack shale. This contributes to the current discussion on whether theatmosphere drives the oceans or vice-versa.

Higher rainfall would have caused increased amounts of freshwater running off the land, carrying large quantities of nutrients intothe oceans, resulting in an increase in marine productivity andsupporting oxygen depletion and a change in circulation patterns in thedeep ocean.

Climate modeling identified that specific periods of extremelyhigh river discharge occurred during maxima in seasonal contrasts whenthe northern equinox (when the sun is directly over the earth'sequator) coincided with perihelon (when the earth passes closest to thesun). It was only during this specific orbital configuration thatfreshwater run-off exceeded a certain threshold, finally to result in arapid change to ocean anoxia.

The findings, reported in Nature, the international weeklyjournal of science, suggest that variations in the water cycle, oncethey have exceeded a certain threshold, are capable of inducing majorenvironmental change in the oceans.

The researchers conclude: 'The results of this studydemonstrate how sensitively and rapidly tropical marine areas close tocontinental margins react to even relatively moderate increases incontinental freshwater discharge.

'The freshwater threshold required to shift sheltered andsemi-enclosed areas of the modern ocean into an anoxic mode are unknownbut the progressive emission of greenhouse gases to the modernatmosphere is gradually shifting Earth towards a greenhouse mode withan accelerated hydrological cycle.'

'At present it is hardly possible to estimate where we are onthe long-term climate trend but once the freshwater threshold ispassed, a substantial impact on biochemical cycling of continentalmargins may be expected.'

Commenting on the Nature paper, Professor Wagner said that themajority of the world's population live in coastal areas, which werethe most vulnerable to natural catastrophes as recorded in thegeological record.

'Understanding the processes and feedbacks controlling carbonand nutrient cycling in the modern world and during past periods ofextreme warmth is therefore critical to separate human impact onclimate from natural variability and underpins the ability to adapt tofuture conditions,' he said.


Professor Wagner, of theInstitute for Research on Environment and Sustainability at NewcastleUniversity, England, worked with colleagues from the Universities ofBremen and Cologne and the GEOMAR Leibniz Institute of Marine Sciencesat Kiel, in Germany, and the Royal Netherlands Institute for SeaResearch (NIOZ) at Texel, Netherlands.

Story Source:

The above story is based on materials provided by University of Newcastle upon Tyne. Note: Materials may be edited for content and length.

Cite This Page:

University of Newcastle upon Tyne. "Can Ancient Rocks Yield Clues About Catastrophes Like Hurricane Katrina?." ScienceDaily. ScienceDaily, 8 September 2005. <www.sciencedaily.com/releases/2005/09/050908080836.htm>.
University of Newcastle upon Tyne. (2005, September 8). Can Ancient Rocks Yield Clues About Catastrophes Like Hurricane Katrina?. ScienceDaily. Retrieved December 18, 2014 from www.sciencedaily.com/releases/2005/09/050908080836.htm
University of Newcastle upon Tyne. "Can Ancient Rocks Yield Clues About Catastrophes Like Hurricane Katrina?." ScienceDaily. www.sciencedaily.com/releases/2005/09/050908080836.htm (accessed December 18, 2014).

Share This

More From ScienceDaily

More Earth & Climate News

Thursday, December 18, 2014

Featured Research

from universities, journals, and other organizations

Featured Videos

from AP, Reuters, AFP, and other news services

Navy Unveils Robot Fish

Navy Unveils Robot Fish

Reuters - Light News Video Online (Dec. 18, 2014) The U.S. Navy unveils an underwater device that mimics the movement of a fish. Tara Cleary reports. Video provided by Reuters
Powered by NewsLook.com
Arctic Warming Twice As Fast As Rest Of Planet

Arctic Warming Twice As Fast As Rest Of Planet

Newsy (Dec. 18, 2014) The Arctic is warming twice as fast as the rest of the planet, thanks in part to something called feedback. Video provided by Newsy
Powered by NewsLook.com
Ivory Trade Boom Swamps Law Efforts

Ivory Trade Boom Swamps Law Efforts

Reuters - Business Video Online (Dec. 17, 2014) Demand for ivory has claimed the lives of tens of thousands of African elephants and now a conservation report says the illegal trade is overwhelming efforts to enforce the law. Amy Pollock reports. Video provided by Reuters
Powered by NewsLook.com
Indictments in West Virginia Chemical Spill Case

Indictments in West Virginia Chemical Spill Case

AP (Dec. 17, 2014) A grand jury indicted four former executives of Freedom Industries, the company at the center of the Jan. 9, 2014 chemical spill in Charleston, West Virginia. The spill contaminated the Elk River and the water supply of 300,000 people. (Dec. 17) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.


Breaking News:

Strange & Offbeat Stories

Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News


Free Subscriptions

Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile

Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?

Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins