At the end of the last Ice Age, approximately 11 500 to 11 000 calendar years ago, mean annual temperatures rose considerably within a few decades. This marked the beginning of the Holocene or Postglacial age. During this era the mean summer temperatures varied very little over the long- term, approximately ±1� C compared to the present. As a result, the movement of the glaciers, which had melted way back into the Alpine valleys at the beginning of the postglacial age, was limited to a small area called the glacier forefield (“Gletschervorfeld”), which in many cases is easily identified today, owing to its meagre vegetation. The forefield is found between the terminal moraine that marks the glaciers' greatest extent (e.g. as in 1850/60) and the glaciers' current limit. Within the postglacial periods of warmer and cooler conditions there have been series of fluctuations from maximum to minimum extensions, some glaciers shrinking to even less than their current state. The last noticeable warm period is called the Mediaeval Climatic Optimum, from around the end of the 8th century to about 1300, and the last marked cold period is called the Little Ice Age (around 1300 to 1850/60). Since glaciers are good indicatiors of climatic change, their fluctuations indirectly reflect the natural variations in climatic conditions since the last Ice Age.

To reconstruct the climatic fluctuations and landscape evolution during the Holocene we also can use pollen analysis, analysis of lake sediments and dendrochronology.
 

1 - The Ried glacier near Gr�chen (Valais). The glacier forefield is bordered by huge moraine ridges which are built up during holocene advances of the Ried glacier.
 

Click on the rectangles in the images in the figure below to see how the Morteratsch and the Tschierva/Rosegg glaciers retreated at the end of the last glacial period (Late glacial) and during the Holocene.

2 - An example of glacier retreat at the end of the last glacial period and during the Holocene.

29 August 2011
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