Mass balance of Vernagtferner, Austria, from 1964/65 to 1996/97: Results for three sections and the entire glacier

In the centre of the highly glacierized Octztal valley, mass balance is determined for the three neighbouring glaciers Hintereisferner, Kesselwandferner and Vernagtferner, applying the direct glaciological method, related to the 'fixed date' system. The diverging behaviour of the three glaciers due to slightly varying local climatic conditions as well as to different topoclimatological and physiographic features gave reason to analyse the Vernagtferner mass balance separately for three easily discernible sections, i.e. Schwarzwand, Taschachjoch and Brochkogel, each showing characteristic aspect and elevational distributions of area respectively. The cumulative mass balance of the Vernagtferner for the period 1968/69, when separate mass balance computations for the three sections were started, until 1996/97 amounted to -8.7 m water equivalent (w.e.). The mass loss of the western Schwarzwand section as the parr with the largest share of low elevation area was -13.3 m w.e., in contrast to the central Taschachjoch section which lost only -6.6 m w.e. The remaining eastern Brochkogel section with a loss of -8.5 m w.e. fits best the mass balance of the total Vernagtferner although its physiographic characteristics differ markedly from those of the entire glacier. The equilibrium line altitude (ELA) dependence on specific net mass balance (b) is slightly different for the three sections, whereas the dependence of the accumulation area-total area ratio (AAR) on b is characterized by nearly identical sensitivities. Moreover, AAR correlates better with b than ELA, therefore AAR is regarded as a more representative parameter for the Vernagtferner than ELA.