The Last Ice Age - Part II Print
Outreach - Showcase
Written by Paolo Zamparutti   
Monday, 27 March 2006
Image The first part of this investigation on the last Ice Age was published on MTG Climate in November. It focused on some aspects of the climate of 21 thousand years ago. Now we can use the data given by the Ice Age 21k simulation to understand what are the fundamental differences between the climate of today and the glacial one: in particular we will focus our attention on the thermal aspect. We will base our studies on a simulation that represents a medium condition of the Wurmian period, when there were some warm and favourable phases and some colder ones.

The average global temperature was, as a whole, inferior to the present one of about 5-6 degrees Celsius, with differences not uniformly distributed. We can note, in fact, that the Southern Hemisphere was colder than the Northern one (in our simulation: -4.6oC in the Southern Hemisphere; -5.7oC in the Northern Hemisphere): this was caused by the greater oceanic area.

Figure 1
Figure 1
 At the Tropics the temperatures were similar to the present ones, with differences of about 1-2 degrees Celsius compared to current days, but they collapsed as we moved towards more higher latitudes, to reach an incredible negative value between the fiftieth and the seventieth parallel in our hemisphere, where the differences reached the 20oC referred to modern times (caused by the wide glacial covering that occupied those latitudes in Europe and North America), then to return comparable to our temperatures in the arctic zones also covered by ice today.

We can note the particularly intense cold condition that insisted on the North Atlantic Ocean (covered by ice, that was present up to the fiftieth parallel), the Scandinavian peninsula and Canada.

Figure 2
Figure 2
 The thermal anomalies increased during winter when enormous thermal anticyclones moved the polar front towards the northern coasts of Africa; the ocean ice extended almost up to the fortieth parallel and snow covered completely our continent, while during summer months they tended to diminish in the ice-free zones.

Figure 3
Figure 3
 In Northern Italy, the average annual temperatures were about 9oC below the ones in modern times, while in the South of our country they reached a difference of 5oC. Winter was absolutely cold and it registered thermal drops of about 15oC in the Padana Plain, that fell around 6oC in Sicily. Much more intense were the conditions present in the nations of Central Europe, with drops of about 30oC in the Scandinavian glacial plate. There were also, in Europe, marked seasonal differences and the thermal anomalies were more intense in winter than in summer. In fact, if winter was dominated by thermal anticyclones that brought extremely low temperatures over Europe (and intense snowfalls only in the Southern part of Italy, often touched by powerful depressions originated from the interaction of the cold air and the warm African ascent), during summer with a lot of probability there was a really solid anticyclonic regime of dynamic nature.

Figure 4
Figure 4
 It was the Azores anticyclone that, however, did not bring an elevated rate of humidity, like in our Summers. So, the heavy insolation over areas with low humidity favoured the rising of the maximum temperatures similar to the present ones on the Mediterranean Sea. Also in this case the thermal anomaly increased as we got closer to the Scandinavian Glacial Plate. For this reason it is possible to think that during summer, normally mild or perhaps warm, there were sudden cold air irruptions of indeterminable violence improbable in our times, with short thunderstorms, for the lack of humidity, but very intense. In some summer nights, following these irruptions, probably the minimum temperatures went below zero in the Padana Plain (larger than the present one, for the low sea level). Summer was a season of big thermal excursions.

Figure 5
Figure 5
 If summer and winter were very drought seasons, for the North of Italy and for our continent, the 'transition seasons', autumn and spring, were the humid ones. The greater part of the precipitations, in fact, concentrated itself in those periods, mainly snowy during the colder months, rainy in the warmer ones. But we will talk in our next article about the precipitations and the disposition of the principal baric figures.

Written by Paolo Zamparutti and translation by Giuseppe Petricca

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