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

Shaw, Thomas E.; Yang, Wei; Ayala, Álvaro; Bravo, Claudio; Zhao, Chuanxi; Pellicciotti, Francesca

Near-surface air temperature (inline-formulaTa) is highly important for modelling glacier ablation, though its spatio-temporal variability over melting glaciers still remains largely unknown. We present a new dataset of distributed inline-formulaTa for three glaciers of different size in the south-east Tibetan Plateau during two monsoon-dominated summer seasons. We compare on-glacier inline-formulaTa to ambient inline-formulaTa extrapolated from several local off-glacier stations. We parameterise the along-flowline sensitivity of inline-formulaTa 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 inline-formulam along the down-glacier flowline distance. Beyond this distance, both the inline-formulaTa on the Tibetan glaciers and global glacier datasets show little additional cooling relative to the off-glacier temperature. In general, inline-formulaTa on small glaciers (with flowline distances inline-formula<1000inline-formulam) 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 inline-formula∼70inline-formula% 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.

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Shaw, Thomas E. / Yang, Wei / Ayala, Álvaro / et al: Distributed summer air temperatures across mountain glaciers in the south-east Tibetan Plateau: temperature sensitivity and comparison with existing glacier datasets. 2021. Copernicus Publications.

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