2011 年 29 巻 p. 19-29
Observations indicate that over the past few decades, valley glaciers and ice caps in the Nepalese Himalaya have been continuously shrinking in response to climate warming. The response timescales of these glaciers are not yet well understood. Considering the case of Glacier AX010, this paper examines several methods for estimating the rate of glacier response to changes in climate. In spite of having simple model physics and requiring only a few and often available field data, simpler analytical methods yield reasonable estimates of timescale. Detailed analytical and numerical ice-flow models suggest that the response times for Glacier AX010 are on the order of 50 years. These magnitudes are slightly larger than field evidence indicates for typical valley glaciers, indicating that Glacier AX010 responds relatively slowly to changing climate. Nonetheless, sustained century-scale warming as forecasted for the Nepalese Himalaya would provide sufficient time for Glacier AX010 to respond to this climatic disequilibrium. Given the fact that the glacier already lacks a persistent accumulation zone, we foresee a complete retreat of the glacier by 2100.