Rolleston Glacier: First decade of mass balance measurement and the implications of climate change on mass balance monitoring

Abstract

Rolleston Glacier is a small glacier located near Arthurs Pass. It is one of only two NZ glaciers at which mass balance is directly measured. After the first decade of monitoring (2011-2020), the cumulative mass balance is -6.8 m w.e., or -0.7 m w.e. per year. Rolleston Glacier is also photographed each year as part of NIWA’s end-of-summer snowline monitoring program. There is a statistically significant relationship between measured annual mass balance and the position of the EOSS (R2 0.89, p=0.0001). However, neither method accurately records ice volume loss in strongly negative years, and sometimes the only remaining mass input on the glacier is derived from snow avalanche off Mt Philistine. This secondary snow input is estimated to be approximately 25% of winter snow accumulation; but the actual volume gained by this process is yet to be determined. A recent purchase of a Riegl VUX-240 laser scanner (pers. comm., J. Brasington), provides new opportunity to supplement the existing field program with geodetic mass balance measurement. Such an approach will not only be more robust in extremely negative years, but will improve understanding of spatial variability in accumulation and ablation processes, and increase our ability to estimate future changes to alpine hydrology.