Determining steady-state accumulation-area ratios of outlet glaciers for application of outlets in climate reconstructions

A steady-state glacier equilibrium-line altitude (ELA) can be determined by the accumulation-area ratio (AAR) method. AAR varies with climate (balance ratio) and glacier type (glacier geometry). The method involves calculating steady-state accumulation area-ratios (AAR0) from mass balance characteristics of glaciers by statistical methods. In order to confirm the application of linear regression to calculate AAR0 in the case of outlet glaciers, a method to reveal the mathematical relationship between annual net balance (bn) and AAR was developed. Analyses carried out on (bn, AAR) data sets for 14 outlet glaciers showed that the best approximation for the (bn, AAR) relationship is linear, with an average squared correlation coefficient of 0.786, but relatively strong non-linearity was detected for several glaciers. A possible explanation lies in the hypsometry of the observed glaciers. Results confirm the application of linear regression to calculation of AAR0s for outlet glaciers. An average AAR0 of 0.58 was estimated as the type-specific AAR0 for outlet glaciers.