Latest Issue

2025 Vol.134 No.4

Rhone Glacier and Climate Change

The Rhone Glacier is changing rapidly. Since the first annual survey in 1874, the glacier has receded 1.9 km, which is an annual average rate of 13 ma^-1.
  The photograph to the left was taken in August 1900 by J.P. Früh, the first geography professor of E.T.H., Switzerland. The image shows the lowest part of the ablation area descending a steep rock wall and forming an icefall. A side-moraine is forming at the left side of the glacier (orographic right-hand side), which dates to the last stage of the Little Ice Age. Further to the left, at the middle, a trace of an older side-moraine is visible, which dates back to the Egesen-Stadium, 12,000–11,000 aBP, indicating the end of the Last Ice Age (Würm in the Alps).
  The image to the right shows the Rhone Glacier in 2004, approximately 100 years later, by late Dr. U. Moser of the author’s institute. The rate of retreat has accelerated in recent years to 20 ma^-1. A small lake appeared in 2004 between the rock wall and the glacier front. Since the lake appears to be permanent, the Swiss Topographic Office (Swisstopo) has given it an official geographic name, Rhonesee (Rhone Glacier Lake). The temperature change between the two images at high-altitude stations (above 2,000 m a.s.l.) in the Alps is 0.15 K per decade, with an accelerating trend. The change became especially prominent after 1980, and in the most recent 45 years, the rate has been 0.42 K per decade.
  Besides the changes to the glacier, the two images show how much the vegetation has changed during the last 100 years. Most visible is an invasion of Swiss Pine (Pinus cembra), which is now common in the upper Rhone Valley. If the climate continues to change at the present rate, the glacier is expected to lose 85% of its surface area by the end of the present century, surviving as a small mountain glacier with its front at about 3,000 m a.s.l.

(Atsumu OHMURA)