Distributed summer air temperatures across mountain glaciers in the south-east Tibetan Plateau: temperature sensitivity and comparison with existing glacier datasets

Near-surface air temperature (T-a) is highly important for modelling glacier ablation, though its spatiotemporal variability over melting glaciers still remains largely unknown. We present a new dataset of distributed T-a for three glaciers of different size in the south-east Tibetan Plateau during two monsoon-dominated summer seasons. We compare on-glacier T-a to ambient T-a extrapolated from several local off-glacier stations. We parameterise the along-flowline sensitivity of T-a on these glaciers to changes in off-glacier temperatures (referred to as temperature sensitivity) and present the results in the context of available distributed on-glacier datasets around the world. Temperature sensitivity decreases rapidly up to 2000-3000 m along the down-glacier flowline distance. Beyond this distance, both the T-a on the Tibetan glaciers and global glacier datasets show little additional cooling relative to the off-glacier temperature. In general, T-a on small glaciers (with flowline distances < 1000 m) is highly sensitive to temperature changes outside the glacier boundary layer. The climatology of a given region can influence the general magnitude of this temperature sensitivity, though no strong relationships are found between along-flowline temperature sensitivity and mean summer temperatures or precipitation. The terminus of some glaciers is affected by other warm-air processes that increase temperature sensitivity (such as divergent boundary layer flow, warm up-valley winds or debris/valley heating effects) which are evident only beyond similar to 70 % of the total glacier flowline distance. Our results therefore suggest a strong role of local effects in modulating temperature sensitivity close to the glacier terminus, although further work is still required to explain the variability of these effects for different glaciers.

Automated summary

The study compared the temperature changes on Tibetan glaciers with ambient temperatures and found that smaller glaciers are highly sensitive to external temperature changes, with the terminus being affected by warm-air processes. Local effects play a strong role in modulating temperature sensitivity near the glacier terminus.