Melting glaciers and soil development in the proglacial area Morteratsch (Swiss Alps): II. Modeling the present and future soil state

Abstract

Climate change due to anthropogenic emissions of greenhouse gases is predicted to increase the average surface temperature. The most evident soil changes in the Alps will occur in proglacial areas where already existing young soils (with an age in most cases of up to 150 years) will continuously develop and new soils will form due to glacier retreat. Based on existing soil chronosequence data and statistical analyses in the proglacial area Morteratsch (Switzerland), the present-day state of the soils as well as their future development in the next 100 years in the existing and new proglacial area has been modeled taking the retreat of the glacier into consideration. The present-day as well as the future soil distribution was modeled using a probabilistic approach. Several soil characteristics have been modeled such as the pH value, the skeleton content, and the soil depth relevant to plant growth. To model soil properties in a future proglacial area (that is now covered by ice), the glacier-bed morphology had to be modeled. The calculations were performed using the cubic Non-Uniform Rational B-Spline (NURBS) curve to parameterize the course of a branch in flow direction. With the help of the ice cap and relief factor the thickness of the glacier was modeled. Climate change was introduced numerically by changing the mass balance of the glacier. For the area of interest a temperature increase of +1.6°C by the year 2050 and +3°C by the year 2100 can be assumed (according to the scenario A1B of IPCC). In the upper part of the proglacial area mostly Skeletic/Lithic Leptosols and Humi-Skeletic Leptosols will be found. In flat parts close to the main river, additional Fluvisols will develop. A considerable part of the upper proglacial area does not have any soil cover. Lithic/Skeletic to Humi- Skeletic Leptosols are modeled on the young lateral moraines. Chronosequences were vital to make any (4D) predictions of soil evolution in the proglacial area. The statistically and probabilistically based model also had, however, its weaknesses. The problems are related to the sediment properties in the glacier bed and the stability of new moraines.