Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Long-awaited breakthrough in the reconstruction of warm climate phases

19.07.2016

AWI researchers decipher the temperature indicator TEX86 and overcome a seeming weakness of global climate models

Scientists from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) have overcome a seeming weakness of global climate models. They had previously not been able to simulate the extreme warm period of the Eocene.


The Roaring Forties

Die "Bruellenden Vierziger"

Copyright: Alfred-Wegener-Institut / Frank Rödel

One aspect of this era that particularly draws interests to climatologists: It was the only phase in recent history when greenhouse gas concentration was as high as researchers predict it to be for the future. The AWI scientists have now found that the apparent model weakness is due to a misinterpretation of the temperature indicator TEX86.

These molecules, which are produced by archaea do not record the surface temperature of the ancient ocean as expected, but rather the temperature of water depths up to 500 metres. In the current issue of the journal Nature Geoscience, the scientists report on this new finding which has now made it possible to correctly simulate the temperature distribution of the Eocene in climate models.

Climate scientists often hear the same complaint: How can climate models accurately predict the future of our planet if it is not even possible to correctly reproduce the climate of the past? One of the unsolved problems was that all previous attempts to simulate the extreme temperatures of the Eocene with climate models failed.

At that time, 49 to 55 million years ago, the carbon dioxide content of the air was likely more than 1000 ppm (parts per million) – i.e. at least two times the current greenhouse gas concentration. The earth warmed up so strongly that the icesheets on Greenland and Antarctica disappeared. Instead of ice crystals, palm trees grew there. "Until recently, we believed that the sea surface temperature near the North Pole at the time was 23 degrees Celsius; in Antarctica, it was believed to have been more than 30 degrees Celsius," says Dr Thomas Laepple, climate researcher at the AWI Potsdam.

These temperature estimates were based on data from the climate indicator TEX86. This abbreviation stands for a ratio of specific organic compounds produced by archaea, depending on the water temperature in which they lived. "Archaea are unicellular organisms that can in part withstand surprisingly high ambient temperatures. The molecules of the organisms that were living at that time are still preserved in the sedimentary layers of the seafloor. They are one of our most important archives for warm climate conditions, but as we have seen, we decoded them wrongly in the past," says Thomas Laepple.

He and his AWI colleague at the time, Sze Ling Ho, first had doubts about the interpretation of the TEX86 temperature indicator during a comparison of climate data from the most recent ice age. The scientists noticed that the TEX86 temperatures were far too cold compared to other geological evidence. "The discrepancy was so obvious that we started to review the TEX86 values of around 3,000 sediment samples from different ocean basins and from different epochs of the Earth. It soon became apparent that the average temperature change inferred from TEX86 was exaggerated, always and on all time scales, by one and a half to two times. The temperature it showed for cold periods was much too cold and the one for warm periods was much too warm," explains geochemist Sze Ling Ho.

The cause of this pattern had to be of a fundamental nature, a suspicion that was confirmed upon closer analysis. "TEX86 had previously been interpreted as an indicator of sea surface temperature, in spite the fact that the archaea that produce TEX86 rarely directly live at the sea surface. Through the comparison with other climate archives, we have been able to constrain the depth in which the TEX86 signal is produced. We now assume that TEX86 represents the water temperature at a depth of up to 500 metres," Sze Ling Ho explains.

At this water depth, the temperature difference between the tropical oceans and the polar seas is smaller than at the surface. This has direct consequences for climate reconstruction, since the information generated from the indicator is differently translated into temperature values. "In practice, the TEX86 extreme values need to be roughly halved in the climate reconstructions. Comparing the corrected temperatures with the models shows that they now reflect the climate of the Eocene in a realistic and physically consistent way," explains Thomas Laepple.

However, we also have to correct our temperature-conception of the Eocene. Thomas Laepple: "The era remains the warmest period of the past 65 million years. The water temperatures that we assumed for the Arctic and Antarctica, though, were overstated by at least ten degrees Celsius. Now, we know that the water in the Southern Ocean had a temperature of about 20 to 25 degrees Celsius at that time. The region was therefore still warm enough for there to be palm trees sprouting on the beach."

Notes for Editors:
The study will be published in Nature Geoscience on the 18th of July 2016, 1600 London time under the following title:
Sze Ling Ho, Thomas Laepple: Flat meridional temperature gradient in the early Eocene in the subsurface rather than surface ocean, Nature Geoscience, July 2016, DOI: 10.1038/NGEO2763

Until the embargo is lifted, please find printable photographs at: http://multimedia.awi.de/medien/pincollection.jspx?collectionName=%7B7c51adf7-18...

Your scientific contact person at the Alfred Wegener Institute is:

• Dr Thomas Laepple (Tel: +49 (0)331 288 - 2159; e-mail: Thomas.Laepple(at)awi.de) If you want to talk to Thomas Laepple, please contact him before the embargo is lifted as he won’t be available from the 18th until the 24th of July.

The co-author Sze Ling Ho can be reached at the Bjerknes Centre for Climate Research at the University of Bergen at tel.: +47 55 58 35 29) (e-mail: ling.ho(at)uib.no).

Your contact in the Communications and Media Department is Sina Löschke (Tel.: +49 (0)471 4831 - 2008; email: medien(at)awi.de).


The Alfred Wegener Institute conducts research in the Arctic, Antarctic and in the high and mid latitude oceans. It coordinates polar research in Germany and provides important infrastructure such as the research icebreaker Polarstern and stations in the Arctic and Antarctic for the international science community. The Alfred Wegener Institute is one of the 18 research centres belonging to the Helmholtz Association, Germany's largest scientific organisation.

Ralf Röchert | idw - Informationsdienst Wissenschaft
Further information:
http://www.awi.de/

More articles from Earth Sciences:

nachricht Fossil coral reefs show sea level rose in bursts during last warming
19.10.2017 | Rice University

nachricht NASA finds newly formed tropical storm lan over open waters
17.10.2017 | NASA/Goddard Space Flight Center

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Electrode materials from the microwave oven

19.10.2017 | Materials Sciences

New material for digital memories of the future

19.10.2017 | Materials Sciences

Physics boosts artificial intelligence methods

19.10.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>