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

<p>Near-surface air temperature (<span class="inline-formula"><i>T</i>_a</span>) 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 <span class="inline-formula"><i>T</i>_a</span> for three glaciers of different size in the south-east Tibetan Plateau during two monsoon-dominated summer seasons. We compare on-glacier <span class="inline-formula"><i>T</i>_a</span> to ambient <span class="inline-formula"><i>T</i>_a</span> extrapolated from several local off-glacier stations. We parameterise the along-flowline sensitivity of <span class="inline-formula"><i>T</i>_a</span> 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 <span class="inline-formula">m</span> along the down-glacier flowline distance. Beyond this distance, both the <span class="inline-formula"><i>T</i>_a</span> on the Tibetan glaciers and global glacier datasets show little additional cooling relative to the off-glacier temperature. In general, <span class="inline-formula"><i>T</i>_a</span> on small glaciers (with flowline distances <span class="inline-formula">&lt;1000</span> <span class="inline-formula">m</span>) 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 <span class="inline-formula">∼70</span> <span class="inline-formula">%</span> 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.</p>