Consolidating the Randolph Glacier Inventory and the Glacier Inventory of China over the Qinghai-Tibetan Plateau and Investigating Glacier Changes Since the mid-20^th Century

Abstract. Glacier retreat in the Qinghai-Tibetan Plateau (QTP), the "third pole of the world", has attracted the attention of researchers worldwide. Glacier inventories in the 1970s and the 2000s provide valuable information to infer changes in individual glaciers. However, individual glacier volumes are either missing, incomplete or have large errors in these inventories, and thus, the use of these datasets to investigate changes in glaciers in QTP in the past few decades has become a challenge, particularly in the context of climate change. In this study, individual glacier volume data in the Randolph Glacier Inventory version 4.0 (RGI 4.0, 1970s) and the second Glacier Inventory of China (GIC-Ⅱ, 2000s) are recalculated and consolidated using a slope-dependent algorithm based on elevation datasets for the QTP. The two consolidated inventories (The data are available under https://doi.org/10.11888/Glacio.tpdc.270390 (Liu, 2020). For the time of review, the data will be accessible through the following review link https://data.tpdc.ac.cn/en/data/4b88e394-0eb4-44c4-aa38-32aeb614daff/.) are validated by comparing the observed and estimated glacier data reported in the literature. The two consolidated glacier inventories are then compared for different mountains over the QTP to detect changes in glacier areas, volumes, fragmentation status, etc. during the past 3–4 decades. Based on the results, the slope-dependent algorithm performed well in computing individual glacier volumes and other elements, compared with the widely used volume-area scaling which often leads to overestimation in the interior Plateau and underestimation in other areas of the QTP in both RGI 4.0 and GIC-Ⅱ. The comparison of the two inventories reveals a total area of glaciers in the QTP of approximately 59026.5 km² in the RGI 4.0 and 44301.2 km² in the GIC-Ⅱ. The total glacier volume is 4045.9 km³ in the GIC-Ⅱ compared with 4716.7 km³ in the RGI 4.0. The results suggest a significant retreat and melting of glaciers in the QTP. However, variations are observed in different glaciers. The Karakoram Mountains contain the largest number of surged glaciers, while the highest level of retreat is observed in the Gandise Mountains. An increase in the fragmentation index is observed in the northern mountains, particularly the Pamir Plateau, which displays the highest trends of glacier movement and deformation. The glacier volumes decrease mainly on south-westward aspects and increase to various extents on the other aspects of most mountains. The consolidation of the glacier inventories and the findings of the analysis performed in this study provide important databases for future glacier-related studies, particularly for investigating the effects of climate change on glaciers in the past and projecting future effects.