Thinning and surface mass balance patterns of two neighboring debris-covered glaciers in southeastern Tibetan Plateau

Abstract. Debris-covered glaciers are a common feature of the mountain cryosphere in the southeastern Tibetan Plateau. A better understanding of these glaciers change is necessary to reduce the uncertainties of the regional water resource variability, and to anticipate potential cryospheric risks. In this study, we quantify seasonal thinning (dh) and surface mass balance (SMB) patterns of two neighboring debris-covered glaciers (23 K Glacier and 24 K Glacier) in the southeastern Tibetan Plateau with repeated unpiloted aerial vehicle (UAV) surveys and in-situ measurements. We observe that the dh pattern of 23 K Glacier is distinct from that of 24 K Glacier, despite their proximity. The dh magnitude of the 23 K Glacier is ~1.4–3.0 times greater than that of the 24 K Glacier at all periods, which is mainly driven by the stronger dynamic state of 24 K Glacier. The contrasted behaviour between the two glaciers is also valid in the early twenty-first century. In contrast, the SMB patterns of the two glaciers are generally in agreement at different periods. The debris thickness distribution correlates with the SMB spatial distribution for both glaciers, while the supraglacial ice cliffs and ponds area density distribution is not correlated with SMB spatial distribution. This high-resolution comparison study of two neighboring glaciers confirms the significance of both glacier dynamic and debris thickness in controlling the thinning and melt for the different type debris-covered glaciers of the southeastern Tibetan Plateau in the context of climate change.