New interpretation of Antarctic ice cores

Mar 02, 2011

Climate researchers at the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association (AWI) expand a prevalent theory regarding the development of ice ages. In the current issue of the journal Nature three physicists from AWI's working group "Dynamics of the Palaeoclimate" present new calculations on the connection between natural insolation and long-term changes in global climate activity. Up to now the presumption was that temperature fluctuations in Antarctica, which have been reconstructed for the last million years on the basis of ice cores, were triggered by the global effect of climate changes in the northern hemisphere. The new study shows, however, that major portions of the temperature fluctuations can be explained equally well by local climate changes in the southern hemisphere.

The variations in the Earth's orbit and the inclination of the Earth have given decisive impetus to the climate changes over the last million years. Serbian mathematician Milutin Milankovitch calculated their influence on the seasonal distribution of insolation back at the beginning of the 20th century and they have been a subject of debate as an astronomic theory of the ice ages since that time. Because land surfaces in particular react sensitively to changes in insolation, whereas the land masses on the Earth are unequally distributed, Milankovitch generally felt insolation changes in the northern hemisphere were of outstanding importance for over long periods of time. His considerations became the prevailing working hypothesis in current as numerous climate reconstructions based on ice cores, marine sediments and other climate archives appear to support it.

AWI scientists Thomas Laepple, Gerrit Lohmann and Martin Werner have analysed again the temperature reconstructions based on ice cores in depth for the now published study. For the first time they took into account that the winter temperature has a greater influence than the summer temperature in the recorded signal in the Antarctic ice cores. If this effect is included in the model calculations, the reconstructed from ice cores can also be explained by local climate changes in the southern hemisphere.

Thomas Laepple, who is currently conducting research at Harvard University in the US through a scholarship from the Alexander von Humboldt Foundation, explains the significance of the new findings: "Our results are also interesting because they may lead us out of a scientific dead end." After all, the question of whether and how climate activity in the is linked to that in the is one of the most exciting scientific issues in connection with our understanding of climate change. Thus far many researchers have attempted to explain historical Earth climate data from Antarctica on the basis of Milankovitch's classic hypothesis. "To date, it hasn't been possible to plausibly substantiate all aspects of this hypothesis, however," states Laepple. "Now the game is open again and we can try to gain a better understanding of the long-term physical mechanisms that influence the alternation of ice ages and warm periods."

"Moreover, we were able to show that not only data from ice cores, but also data from marine sediments display similar shifts in certain seasons. That's why there are still plenty of issues to discuss regarding further interpretation of palaeoclimate data," adds Gerrit Lohmann. The AWI physicists emphasise that a combination of high-quality data and models can provide insights into climate change. "Knowledge about times in the distant past helps us to understand the dynamics of the climate. Only in this way will we learn how the Earth's climate has changed and how sensitively it reacts to changes."

To avoid misunderstandings, a final point is very important for the AWI scientists. The new study does not call into question that the currently observed climate change has, for the most part, anthropogenic causes. Cyclic changes, as those examined in the Nature publication, take place in phases lasting tens of thousand or hundreds of thousands of years. The drastic emission of anthropogenic climate gases within a few hundred years adds to the natural rise in greenhouse gases after the last ice age and is unique for the last million years. How the climate system, including the complex physical and biological feedbacks, will develop in the long run is the subject of current research at the Alfred Wegener Institute.

Explore further: NASA sees Typhoon Matmo making second landfall in China

More information: Laepple, T., M. Werner, and G. Lohmann, 2011: Synchronicity of Antarctic temperatures and local solar insolation on orbital time scales. It will be published inNature on 3 March 2011 (doi:10.1038/nature09825).

Related Stories

Antarctic snow inaccurate temperature archive

Feb 15, 2006

According to Dutch researcher Michiel Helsen, annual and seasonal temperature fluctuations are not accurately recorded in the composition of the snow of Antarctica. His research into the isotopic composition ...

Ice core studies confirm accuracy of climate models

Sep 11, 2008

An analysis has been completed of the global carbon cycle and climate for a 70,000 year period in the most recent Ice Age, showing a remarkable correlation between carbon dioxide levels and surprisingly abrupt changes in ...

Critical turning point can trigger abrupt climate change

Apr 20, 2009

Ice ages are the greatest natural climate changes in recent geological times. Their rise and fall are caused by slight changes in the Earth's orbit around the Sun due to the influence of the other planets. But we do not know ...

Strong regional climatic fluctuations in the tropics

Dec 02, 2009

Climatic fluctuations close to the equator show a different pattern to climate change in the Arctic and Antarctic. In the tropics distinct 11500 year fluctuations between wet and dry periods can be clearly identified which ...

Ice cores map dynamics of sudden climate changes

Jun 19, 2008

New, extremely detailed data from investigations of ice cores from Greenland show that the climate shifted very suddenly and changed fundamentally during quite few years when the ice age ended. Researchers ...

Recommended for you

Fires in Central Africa During July 2014

27 minutes ago

Hundreds of fires covered central Africa in mid-July 2014, as the annual fire season continues across the region. Multiple red hotspots, which indicate areas of increased temperatures, are heavily sprinkled ...

NASA's HS3 mission spotlight: The HIRAD instrument

10 hours ago

The Hurricane Imaging Radiometer, known as HIRAD, will fly aboard one of two unmanned Global Hawk aircraft during NASA's Hurricane Severe Storm Sentinel or HS3 mission from Wallops beginning August 26 through ...

Fires in the Northern Territories July 2014

Jul 23, 2014

Environment Canada has issued a high health risk warning for Yellowknife and surrounding area because of heavy smoke in the region due to forest fires. In the image taken by the Aqua satellite, the smoke ...

How much magma is hiding beneath our feet?

Jul 23, 2014

Molten rock (or magma) has a strong influence on our planet and its inhabitants, causing destructive volcanic eruptions and generating some of the giant mineral deposits. Our understanding of these phenomena ...

User comments : 0