Calculating equilibrium-line altitudes of former glaciers by the balance ratio method: a new computer spreadsheet

Abstract

Equilibrium-line altitudes (ELAs) of former glaciers are commonly reconstructed using the accumulation-area ratio method, based on the assumption that the accumulation area of the glacier occupies some fixed proportion of the total glacier area. However, this method takes no account of glacier hypsometry, and is therefore subject to large errors in regions where glaciers exhibit a wide range of shapes and sizes. A more rigorous balance ratio method was introduced by Furbish and Andrews (1984) based on idealized mass-balance curves and glacier hypsometry, but is laborious and time-consuming to apply. We introduce a spreadsheet program which will rapidly calculate glacier ELAs using the balance ratio method, and which allows hypsometric variations to be accounted for in ELA reconstructions.