Modelling the Spatial Extent of Franz Josef Glacier, New Zealand from Environmental Variables Using Remote Sensing and GIS

Abstract

This study attempts to model the spatial extent of Franz Josef Glacier in the Southern Alps of New Zealand from environmental variables. Glacier tongue length, area, and equilibrium line altitude were measured in ArcView after 15 end‐of‐summer glacier termini were demarcated from a diverse source of remotely sensed materials that had been geometrically rectified. These tongue parameters were correlated with and regressed against mean winter (June to September) precipitation, summer (December to February) temperature, and terminal gradient. The regressed length model was used to simulate the spatial extent of the glacier tongue in ArcInfo. Modelling of the spatial extent was implemented in a two‐stage approach using Arc Macro Language. The terminus end of the glacier tongue was simulated with an empirical parabolic curve. It is found that the averaging duration of climatic variables plays a significant role in exploring their impact on the glacier tongue. Tongue area has a Pearson correlation coefficient of 0.70 and 0.60, respectively, with mean monthly winter precipitation and averaged monthly summer temperature. The underlying topography exerts a significant effect on tongue morphometry that is most reliably predicted from slope gradient (β) but less so from precipitation (PPT) and temperature (T). The best models for tongue length and area are Length=4100.779−1.2346×PPT+91.9162×T−29.30×β (R²=80.77%) and Area=308.3207−0.0342×PPT+3.3100×T−0.9893×β (R²=81.51%). Through its horizontal shifting and rotation, the empirical parabolic curve enabled the terminal end of the glacier tongue to be accurately and realistically modelled from the environmental variables.