Digital elevation models provide information on aufeis fields in trans-Himalaya

A team of geographers from the South Asia Institute of Heidelberg University has studied the thickness and volume of the as yet under-explored aufeis fields in the Trans-Himalayan region of Ladakh in India.

The team, led by Prof. Dr. Marcus Nüsser, used digital terrain models from high-resolution remote sensing data and terrestrial images to compare the volume of naturally occurring ice and artificially created ice reservoirs. The difference between winter and summer terrain models provides information about the nature of the seasonal ice deposits and the underlying hydrogeological conditions.

Aufeis is a hydrological phenomenon that occurs particularly in cold-arid and permafrost regions. It develops during the winter months through successive freezing of spring water or along small streams. The ice layers can reach thicknesses of several meters and contribute significantly to the local water supply, especially in spring.

In the Trans-Himalaya of Ladakh the accumulation of aufeis is occasionally enhanced in ice reservoirs. Previous studies had already proven the widespread distribution of aufeis in Ladakh and parts of the Tibetan Plateau.

With the goal of gaining new insights into the composition of these seasonal ice accumulations, Prof. Nüsser’s team investigated the thickness and volume of two natural aufeis fields and two artificially constructed ice reservoirs in Ladakh.

During field studies in the fall of 2022 and spring of 2023, the researchers took several thousand photographs of both ice reservoirs and combined them with images from the Pléiades satellite of all four locations at the time of the site visits. The team then generated digital elevation models, calculating a total aufeis volume of up to 302,000 cubic meters.

The natural aufeis fields proved to be larger in area and thicker than the ice accumulations in the artificial reservoirs, with ice thickness measuring more than three meters in isolated cases.

The current findings indicate that large amounts of ground water reach the surface during the winter months. Because the water overflow occurs at the same points every year, the formation of aufeis fields might also provide information on the hydrogeological properties of the near-surface aquifer, explains Dr. Dagmar Brombierstäudl.

“Our research shows that aufeis fields are not isolated but are widely distributed and retain large amounts of water. Nonetheless, this phenomenon has yet to be considered in hydrological models,” stresses Prof. Nüsser.

The high-resolution satellite images proved to be especially valuable for the analysis of the aufeis fields. “The images also allow us to study remote or even inaccessible places. This lets us draw profound conclusions about the formation and composition of aufeis fields and thus develop a better understanding of the aufeis phenomenon as well as determine the impact of climate change,” states the scientist, who heads the Department of Geography at Heidelberg University’s South Asia Institute.

The research work was part of a project on the significance of aufeis and ice reservoirs for climate change adaptation in the Trans-Himalaya of Ladakh. The results of the study were published in the journal Science of the Total Environment.