Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Has the puzzle of rapid climate change in the last ice age been solved?

19.08.2014

Over the past 100 000 years cold temperatures largely prevailed over the planet in what is known as the last ice age. However, the cold period was repeatedly interrupted by much warmer climate conditions.

Scientists have long attempted to find out why these drastic temperature jumps of up to ten degrees took place in the far northern latitudes within just a few decades.


Figure A: The Northern Hemisphere in a cold (stadial) phase

Alfred-Wegener-Institut


The Northern Hemisphere in a warm phase (a brief, warm interstadial phase during glacial climates)

Alfred-Wegener-Institut

Now, for the first time, a group of researchers at the Alfred Wegener Institute (AWI), has been able to reconstruct these climate changes during the last ice age using a series of model simulations. The surprising finding is that minor variations in the ice sheet size can be sufficient to trigger abrupt climate changes.

During the last ice age a large part of North America was covered with a massive ice sheet up to 3km thick. The water stored in this ice sheet is part of the reason why the sea level was then about 120 meters lower than today. Young Chinese scientist Xu Zhang, lead author of the study who undertook his PhD at the Alfred Wegener Institute, explains.

“The rapid climate changes known in the scientific world as Dansgaard-Oeschger events were limited to a period of time from 110,000 to 23,000 years before present. The abrupt climate changes did not take place at the extreme low sea levels, corresponding to the time of maximum glaciation 20,000 years ago, nor at high sea levels such as those prevailing today - they occurred during periods of intermediate ice volume and intermediate sea levels.”

The results presented by the AWI researchers can explain the history of climate changes during glacial periods, comparing simulated model data with that retrieved from ice cores and marine sediments.

How rapid temperature changes might have occurred during times when the Northern Hemisphere ice sheets were at intermediate sizes (see schematic depictions on http://bit.ly/1uQoI70).

During the cold stadial periods of the last ice age, massive ice sheets covered northern parts of North America and Europe. Strong westerly winds drove the Arctic sea ice southward, even as far as the French coast.

Since the extended ice cover over the North Atlantic prevented the exchange of heat between the atmosphere and the ocean, the strong driving forces for the ocean currents that prevail today were lacking. Ocean circulation, which is a powerful “conveyor belt” in the world’s oceans, was thus much weaker than at present, and consequently transported less heat to northern regions.

During the extended cold phases the ice sheets continued to thicken. When higher ice sheets prevailed over North America, typical in periods of intermediate sea levels, the prevailing westerly winds split into two branches. The major wind field ran to the north of the so-called Laurentide Ice Sheet and ensured that the sea ice boundary off the European coast shifted to the north. Ice-free seas permit heat exchange to take place between the atmosphere and the ocean.

At the same time, the southern branch of the northwesterly winds drove warmer water into the ice-free areas of the northeast Atlantic and thus amplified the transportation of heat to the north. The modified conditions stimulated enhanced circulation in the ocean. Consequently, a thicker Laurentide Ice Sheet over North America resulted in increased ocean circulation and therefore greater transportation of heat to the north. The climate in the Northern Hemisphere became dramatically warmer within a few decades until, due to the retreat of the glaciers over North America and the renewed change in wind conditions, it began to cool off again.

“Using the simulations performed with our climate model, we were able to demonstrate that the climate system can respond to small changes with abrupt climate swings,” explains Professor Gerrit Lohmann, leader of the Paleoclimate Dynamics group at the Alfred Wegener Institute, Germany. In doing so he illustrates the new study’s significance with regards to contemporary climate change. “At medium sea levels, powerful forces, such as the dramatic acceleration of polar ice cap melting, are not necessary to result in abrupt climate shifts and associated drastic temperature changes.”

At present, the extent of Arctic sea ice is far less than during the last glacial period. The Laurentide Ice Sheet, the major driving force for ocean circulation during the glacials, has also disappeared. Climate changes following the pattern of the last ice age are therefore not to be anticipated under today’s conditions.

“There are apparently some situations in which the climate system is more resistant to change while in others the system tends toward strong fluctuations,” summarises Gerrit Lohmann. “In terms of the Earth’s history, we are currently in one of the climate system’s more stable phases. The preconditions, which gave rise to rapid temperature changes during the last ice age do not exist today. But this does not mean that sudden climate changes can be excluded in the future.”

Notes for Editors:

The original paper was published in Nature under the following title:

Xu Zhang, Gerrit Lohmann, Gregor Knorr, Conor Purcell: Abrupt glacial climate shifts controlled by ice sheet changes. Nature, DOI: 10.1038/nature13592 (Link: http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13592.html)

Your scientific contact persons at the Alfred Wegener Institute are:

• Xu Zhang (tel.: +49 471 4831-1880; e-mail: Xu.Zhang@awi.de).
• Prof. Dr. Gerrit Lohmann (tel.: +49 471 4831-1758, e-mail: Gerrit.Lohmann@awi.de)
• Dr. Gregor Knorr (tel.: +49 471 4831-1769, e-mail: Gregor.Knorr@awi.de)

Your contact person in the Dept. of Communications and Media Relations is Sina Löschke ( tel. +49 471 4831-2008; e-mail: medien@awi.de).

Follow the Alfred Wegener Institute on Twitter (https://twitter.com/AWI_Media) and Facebook (http://www.facebook.com/AlfredWegenerInstitute). In this way you will receive all current news as well as information on brief everyday stories about life at the institute.

The Alfred Wegener Institute conducts research in the Arctic, Antarctic and oceans of the high and mid-latitudes. It coordinates polar research in Germany and provides major infrastructure to the international scientific community, such as the research icebreaker Polarstern and stations in the Arctic and Antarctica. The Alfred Wegener Institute is one of the 18 research centres of the Helmholtz Association, the largest scientific organisation in Germany.

Weitere Informationen:

http://bit.ly/1uQoI70
http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13592.html

Sina Löschke | idw - Informationsdienst Wissenschaft

Further reports about: Arctic Atlantic Helmholtz-Zentrum Meeresforschung conditions explains heat levels temperature winds

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Atomic precision: technologies for the next-but-one generation of microchips

In the Beyond EUV project, the Fraunhofer Institutes for Laser Technology ILT in Aachen and for Applied Optics and Precision Engineering IOF in Jena are developing key technologies for the manufacture of a new generation of microchips using EUV radiation at a wavelength of 6.7 nm. The resulting structures are barely thicker than single atoms, and they make it possible to produce extremely integrated circuits for such items as wearables or mind-controlled prosthetic limbs.

In 1965 Gordon Moore formulated the law that came to be named after him, which states that the complexity of integrated circuits doubles every one to two...

Im Focus: Researchers demonstrate size quantization of Dirac fermions in graphene

Characterization of high-quality material reveals important details relevant to next generation nanoelectronic devices

Quantum mechanics is the field of physics governing the behavior of things on atomic scales, where things work very differently from our everyday world.

Im Focus: Graphene: A quantum of current

When current comes in discrete packages: Viennese scientists unravel the quantum properties of the carbon material graphene

In 2010 the Nobel Prize in physics was awarded for the discovery of the exceptional material graphene, which consists of a single layer of carbon atoms...

Im Focus: Transparent - Flexible - Printable: Key technologies for tomorrow’s displays

The trend-forward world of display technology relies on innovative materials and novel approaches to steadily advance the visual experience, for example through higher pixel densities, better contrast, larger formats or user-friendler design. Fraunhofer ISC’s newly developed materials for optics and electronics now broaden the application potential of next generation displays. Learn about lower cost-effective wet-chemical printing procedures and the new materials at the Fraunhofer ISC booth # 1021 in North Hall D during the SID International Symposium on Information Display held from 22 to 27 May 2016 at San Francisco’s Moscone Center.

Economical processing

Im Focus: Trojan horses for hospital bugs

Staphylococcus aureus usually is a formidable bacterial pathogen. Sometimes, however, weakened forms are found in the blood of patients. Researchers of the University of Würzburg have now identified one mutation responsible for that phenomenon.

Staphylococcus aureus is a bacterium that is frequently found on the human skin and in the nose where it usually behaves inconspicuously. However, once inside...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Networking 4.0: International Laser Technology Congress AKL’16 Shows New Ways of Cooperations

24.05.2016 | Event News

Challenges of rural labor markets

20.05.2016 | Event News

International expert meeting “Health Business Connect” in France

19.05.2016 | Event News

 
Latest News

Rutgers scientists help create world's largest coral gene database

24.05.2016 | Earth Sciences

New technique controls autonomous vehicles on a dirt track

24.05.2016 | Information Technology

Programmable materials find strength in molecular repetition

24.05.2016 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>