Climatic and Topographic Controls on the Global Distribution of Surge-type Glaciers: Implications for a Unifying Model of Surging

Abstract:

Controls on the global distribution of surge-type glaciers hold the keys to a better understanding of surge mechanisms. Our study represents the first investigation of the correlations between the global distribution of surge-type glaciers and climatic and geometric variables, using a new geodatabase inventorying all surge-type glaciers in the world. The highest densities of surge-type glaciers occur within an optimal climatic envelope bounded by temperature and precipitation. Across all regions with both surge-type and normal glaciers, the former are larger, especially at the cold, dry end of the climatic spectrum. Climate change can also alter the distribution of surge-type glaciers. A species distribution model, Maxent, accurately depicts the major clusters of surge-type glaciers using three variables: temperature, precipitation and glacier area, but under-predicts clusters found outside of the climatically optimal surge zone. We interpret the results in terms of a new enthalpy cycle model. Steady states require a balance between enthalpy gains generated by the balance flux and losses via heat conduction and meltwater discharge. This condition can be most easily satisfied in cold, dry environments (thin, low-flux glaciers, efficient conductive heat losses), and warm, humid environments (high meltwater discharges). Intermediate conditions correspond with the optimal surge zone, where neither heat conduction nor runoff can effectively discharge heat gains, and enthalpy cycling can result.