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The Last Ice Age - Part I |
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Outreach -
Showcase
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Written by Paolo Zamparutti
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Monday, 07 November 2005 |
 Our first Commmunity Showcase article was written by Paolo Zamparutti of MTG Climate in Italy, and was translated by Giuseppe Petricca. MTG Climate used EdGCM to recreate the climatic conditions of 21 thousand years ago, when our planet was at the peak of the last Ice Age (i.e. The Last Glacial Maximum).
Six thousand years ago the Sumers, a people of Mesopotamia, adopted cuneiform writing and from there human history began. From then on the development of humanity has been so intense and rapid to be able to influence the climate of our planet, owing to the production of greenhouse gases coming from its innumerable activities.
Such a fast development, which has forced mankind to occupy every corner of the planet, has been possible due to favourable climatic conditions.
In fact at the end of the last Ice Age (Wurm), temperatures rose and large continental zones were freed from ice. In short we are living now in a very favourable period, unusually hot, if we consider that the history of this planet was not so rosy. In the last two million years (the period that is called Pleistocene and that ends with the last Ice Age), this planet has gone through several Ice Ages, all separated by relatively short periods of warm weather. Many times glaciers have advanced, in the Alps, to the point of touching the plains, digging and modeling valleys.
The average global temperature was 7/8oC less than the present one, but with important differences between the Equator (-1/2 oC as regards today's), the tropical zones (-4/5 oC.) and the boreal zones (-12/14 oC but reaching notably less tips in those parts that were then covered with ice). The causes of this thermic fluctuation are today debated, but the theory that receives the most consents is the astronomical one, which has already been discussed in these papers (see the reference at the end of this article).
Thanks to the simulations of the MTG Climate we are able to recreate, with a good approximation, the conditions of the climate during a period that was not exactly ideal for the human race: twenty-one thousand years ago our planet was right in the middle of the last Ice Age, imprisoned in very large glaciers that changed the look and influenced its climate during the period in which the wurmian glaciation advanced.
 Snow and Ice coverage - Image by MTG Climate
Forty million square kilometers of the terrestrial surface, equal to 25% of the continental extension, was covered by glaciers.
We can observe that in the Northern hemisphere there were three principal ice regions. In the North-American continent the glacial covering went from the Pacific coast to the Atlantic one going down till the forty-ninth parallel on the south-west and it reached the fortieth in south-eat.
On the West there was the glacial region that occupied most of the Rocky mountains, called the "Cordilleran"; on the east there was the glacial plate called "Laurentide" where now is Hudson Bay. It was 4000 meters thick and was connected to the Greenlandic glaciers.
Europe was covered by the Scandinavian glaciers that, thanks also to the low levels of the seas, went down to Great Britain. Close to Scandinavia, ice reached the maximum thickness of about 3000 meters and it got thinner towards east where it reached the Barents Sea and the peninsula of Kara, while more down south, in the principal alpine valleys the thickness of the ice was about 1800 meters. As we will see in the next articles, the presence of such massive ice caps had an enormous impact on the climatic configurations of that period.
The oceanic configuration had been changed, if we look at it with today's rules.
The presence of glaciers in the seas at such a low latitude indicated a very low temperature of the waters and a path of the Gulf Stream with radical differences.
 Ocean SST - Data courtesy of NOAA, Image by MTG Climate
We can notice the wurmian ice age and the following reheating of our days.
The glacial phase is not constant, but it presents different periods of particularly cold weather and others which were relatively milder. In fact scholars divide the last ice age in four distinct phases which can be traced easily in the glacial variations of the Alps.
With the next article we will go through a simulation, trying to understand the deep changes of the circulation of the atmosphere that the ice age brought along.
Bibliography
- Noaa Paleoclimate Center, North-Atlantic Sea Surface Temperature Reconstruction, Bard, E., 2003
- M. Pinna, Le variazioni del Clima, Milano, F. Angeli, 1996
- A. Navarra, A. Pinchera, Il clima, Roma, GLF editori Laterza, 2000
- Carta della glaciazione wurminana in Friuli (Italy)
- Ice Age, in www.nationmaster.com/Encyclopedia
- Quaternary environments climate and climatic changes
Translation by Giuseppe Petricca (
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) and Ken Mankoff
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