Fluctuations of Climate and Glaciers in the Bernese Oberland, Switzerland, and their Geoecological Significance, 1600 to 1975^∗

Abstract

Huge moraine masses and changes in area and volume of ice that have occurred since A.D. 1600 seem to indicate significant climatic fluctuations. On the other hand, the upper timberline, an ecologically sensitive element, appears to show no significant change in altitude over the same period. The extent and mechanisms of long- and short-term climatic fluctuations are assessed and their influence on the geoecological elements of an alpine area are evaluated.

Climatic deteriorations during the last three and one-half centuries, including the Little Ice Age, are discussed in relation to glacier advances, historical weather observations, and instrumental measurements from 1755 to 1965. Instrumental records of summer temperature show no trend from the Little Ice Age to the present while spring and autumn have positive trends during the period of major glacier recession since 1860.

The long-term climatic fluctuations, shown by the long lasting larger extension of the glaciers during the Little Ice Age, seems to coincide with a somewhat higher snowfall frequency during the summer months and a lower level in seasonal mean temperature (spring, autumn, and winter) during the period of observation.

The short-term climatic fluctuations, superimposed upon the long-term effect, show an uninterrupted succession of unfavorable years with cold, wet summers of generally less than a decade. Within this period their effect on the individual elements of the mountain ecosystem were very different:

(1) The glaciers reacted in regard to their size and drainage area with strong advances and significant moraine accumulations, and the equilibrium line fell approximately 200 m.

(2) The upper timberline was damaged and its regenerating ability reduced, but it appears to have outlasted the critical years without essential altitude changes.

(3) Above the timberline on the alpine pasture a few years with catastrophic climatic conditions were sufficient to bring about superficial destruction and soil erosion processes.

(4) In alpine agriculture 1 yr with catastrophic weather damaged production heavily; a repetition of such years could lead to famine.

It is proposed that the climatic fluctuations of the last 3 centuries were similar for certain periods of the last 10,000 yr, during which time geomorphic and palynological evidence indicate that glacier fluctuations were comparable. This also throws emphasis on the conditions of the present century, which have so far been extremely favorable to human use of the Alps. It can be inferred that a reversal could occur within a very short period.