The Cryosphere Relative effect of slope and equilibrium line altitude on the retreat of

Abstract. It has been observed that a majority of glaciers in the Himalayas have been retreating. In this paper, we show that there are two major factors which control the ad-vance/retreat of the Himalayan glaciers. They are the slope of the glacier and changes in the equilibrium line altitude. While it is well known, that these factors are important, we propose a new way of combining them and use it to pre-dict retreat. The functional form of this model has been derived from numerical simulations using an ice-flow code. The model has been successfully applied to the movement of eight Himalayan glaciers during the past 25 years. It explains why the Gangotri glacier is retreating while Zemu of nearly the same length is stationary, even if they are subject to simi-lar environmental changes. The model has also been applied to a larger set of glaciers in the Parbati basin, for which re-treat based on satellite data is available, though over a shorter time period.