It is well known that Alpine glaciers are receding since the end of the so called Little Ice Age. i.e. since about 1850. This is usually attributed to man’s growing impact on the climate through the release of greenhouse gases into the atmosphere. While there is undoubtedly some influence of man on our environment at large on Earth, it is interesting to study time periods where man’s influence was likely negligible. This comprises almost the entire Holocene, i.e. the last 10,000 years since the end of the last big Ice Age. A sensitive proxy for small climate changes are the Alpine glaciers. As it turns out, there were several distinct periods during the Holocene, were glaciers were smaller than today, allowing in some periods the growth of trees in areas, which even now are still covered with ice. In this presentation, some methods to establish these time periods will be discussed. This includes 14C dating of organic material trapped in moraines and/or freed from the receding glaciers, and exposure dating with in-situ produced cosmogenic radionuclides in rocks (10Be, 26Al, 36Cl). Together with tree-line movements, often dated by dendrochronological methods, glacier and temperature variations can be traced throughout the Holocene. I will finally touch upon the intriguing question ‘How did it all happen?’ It is possible – but not yet established – that minor variations in the solar activity may provide the trigger for processes which have a rather big impact on the climate in Alpine regions, both in the European Alps and in the Alps of the southern island of New Zealand, where these changes have been observed as well.
Argonne Physics Division Colloquium Schedule