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Mass Balance and Climate Interactions at Brewster Glacier 2004-5

Laurel George
Department of Geography, University of Otago, Dunedin, New Zealand

 
Abstract

The recognition of glaciers as important indicators of climate and the lack of direct measurements in New Zealand highlights the need for a glacier mass balance program in the Southern Alps. This thesis addresses this gap by measuring mass balance directly at the Brewster Glacier. Through direct measurements using snow pits and ablation stakes, volume and surface change across the entire glacier were calculated and the mass balance gradient and equilibrium line altitude (ELA) was determined. A climate station recorded local climate variables and a Sonic Ranger 50 (SR50) was installed to measure ablation hourly. Historic fluctuations were investigated using photographs of the EOSS taken since 1978 and the EOSS values were compared to the calculated ELA.

During this study a positive mass balance was measured at the Brewster Glacier in 2004/5. The calculated volume gain measured from 1630 km³ to 1780 km³ with a surface rise of 0.64-0.70 m w.e. averaged over the entire glacier. Accumulation was measured as 6540 km³ volume gain or 2.57 m w.e. surface gain and ablation was measured as -4910 km³ volume loss or -1.98 m w.e. surface loss. A linear mass balance gradient from the lowest to the highest stake was calculated as 10 mm w.e./m, though it was better represented by two slopes with a shift in slope at the approx height of the ELA. The ELA calculated from the mass balance gradient was 1784 m, which was very similar to the value derived from the EOSS which was 1780 m. A complex relationship was found between climate variables and ablation and the combination of climate variables explained the most melt at 36%.

Through direct measurements, this study established a mass balance monitoring program at Brewster Glacier and initiated a long-term study. With this data, New Zealand will be able to make contributions to the World Glacier Monitoring Service, proving a better understanding of global fluctuations in mass balance values.

 
Reference

George, L. (2005): Mass balance and climate interactions at Brewster Glacier 2004-5. Unpublished MSc thesis, in Geography, University of Otago, Dunedin, New Zealand.

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