Time Lapse Camera Images for Observation and Visualization of Snow Lines on two Benchmark Glaciers in High Asia – Zhadang and Halji

Abstract:

Glaciers are characteristic elements of high mountain environments and represent key indicators for the ongoing climate change. The covering snowpack considerably affects the glacier-ice surface temperature and thus the meltdown of the glaciers which in recent decades has been accelerating worldwide. Therefore, the detailed investigation of the transient snow is of high importance.

Zhadang Glacier is located in the Nyainqentanglha Mountain Range on the central part of the Tibetan Plateau (30°28.24’ N, 90°38.69’ E). The glacier is debris-free and flows from 6,090 to 5,515 m a.s.l. Recent measurements have shown that the whole glacier is below the ELA and experiences significant glacier volume loss. In May 2010 two terrestrial cameras had been installed there and were continuously operating until September 2012 generating 6,225 images of the glacier with a frequency of three resp. six images per day.

In order to use this dataset for snow line mapping all images had to be georeferenced and orthorectified. The biggest challenge was the problem of shifting camera positions due to deformations of the ground and hence the offset in the image coordinates. This was resolved by combining the manual orthorectification of one image per week with a subsequent spline interpolation to determine the changed image coordinates. The actual orthorectification was finally realized by applying a fully automated batch processing of all images.

The most favorable image of each day was chosen for the manual snow line mapping process. The final aim was the calculation of the mean elevation of the snow line for every day of the data collecting period materialized by intersecting the mapped snow lines with resampled SRTM 3 data. Considering the fact that there were several weeks either with full snow cover or without any snow this aim could be achieved. The findings have been used for the evaluation of a glacier mass balance model developed at RWTH Aachen, Germany, showing a high level of congruence. Another result is the proof of intense ablation due to snow drift and sublimation during the winter months.

In 2014 a similar camera system was installed near Halji Glacier in northwestern Nepal on the southern edge of the Tibetan Plateau (30°15.80’ N, 81°28.16’ E; 5,730 - 5,270 m a.s.l.; ELA = 5,660 m a.s.l.). The images are currently being processed.