Sensitivity of mass balance of five Swiss glaciers to temperature changes assessed by tuning a degree-day model

A degree-day model is used to assess the sensitivity of the mass balance of five Swiss glaciers to temperature changes. The model uses temperature data extrapolated from nearby climate stations, and is tuned by varying precipitation to make the model fit the observed distribution of mass balance with altitude. Once the model is tuned, the effect of temperature change is simulated by recalculating the mass balance with the same parameters as before, but with a temperature increase of 1°C throughout the year. The largest mass-balance changes involving increased ablation of > 1 m w.e. a-1°C-1, occur at the snout, with a progressively smaller increase with altitude. The area-averaged sensitivities for the five glaciers are -0.7 to -0.9 m w.e. a-1 °C-1. If annual precipitation also increased by 20% it would partly offset the effect of the 1°C higher temperatures but could not compensate for it.