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Ablation at the terminus of the Franz Josef Glacier

Eleri Evans
Department of Geography, University of Otago, Dunedin, New Zealand

 
Abstract

This study examines the ablation processes occurring at the terminus of a low lying temperate New Zealand glacier. Melt is assessed at the terminus of the Franz Josef Glacier in relation to climate variables determined by the overall synoptic situation. This study aims to identify which synoptic situations have the greatest influence on the rate of ablation. Daily ablation is measured using twenty ablation sakes distributed over the terminus, for a period of fifty summer days. Daily synoptic weather maps are analysed in terms of the most influential factors on ablation. Ablation is modelled using Braithwaite's (1980) degree-day method requiring mean temperatures to be known. Response time is determined using the Johannesson et al. (1989) equation. This derives the response time by dividing the maximum thickness of the glacier by the annual ablation at the terminus. Daily ablation is highly variable throughout the study period and is regulated mainly by the temperature regime, though precipitation events may have some influence. The highest ablation occurs when a high pressure system is situated over Franz Josef or to the northwest of the South Island. The lowest melt is produced by low pressure systems situated to the southwest and frontal activity. The degree-day method of modelling ablation at the terminus of the Franz Josef Glacier suggests a total of 23 m for the last glacier year. The response time derived suggests that the Franz Josef Glacier has a short response time of 9 - 13 years for changes in climatic forcings. From this study it can be seen that the temperature regime has the most impact upon ablation at the terminus of the Franz Josef Glacier, and that this is due to the importance of the convective fluxes, rather than solar radiation. This illustrates the need for more analysis concerning the role of advection and the wind regime. Placing the processes at Franz Josef Glacier into a wider context of New Zealand alpine glaciers will increase understanding of temperate glacier behaviour in response to climate change.

 
Reference

Evans, E. 2003. Ablation at the terminus of the Franz Josef Glacier. Unpublished Bsc (hons) dissertation, in Geography, University of Otago, Dunedin, New Zealand. 58 pp.

© 2009 Department of Geography, University of Otago, Dunedin, New Zealand