Reconstruction of the Historical (1750–2020) Mass Balance of Bordu, Kara-Batkak and Sary-Tor Glaciers in the Inner Tien Shan, Kyrgyzstan

Abstract

The mean specific mass balance of a glacier represents the direct link between a glacier and the local climate. Hence, it is intensively monitored throughout the world. In the Kyrgyz Tien Shan, glaciers are of crucial importance with regard to water supply for the surrounding areas. It is therefore essential to know how these glaciers behave due to climate change and how they will evolve in the future. In the Soviet era, multiple glaciological monitoring programs were initiated but these were abandoned in the nineties. Recently, they have been re-established on several glaciers. In this study, a reconstruction of the mean specific mass balance of Bordu, Kara-Batkak and Sary-Tor glaciers is obtained using a surface energy mass balance model. The model is driven by temperature and precipitation data acquired by combining multiple datasets from meteorological stations in the vicinity of the glaciers and tree rings in the Kyrgyz Tien Shan between 1750 and 2020. Multi-annual mass balance measurements integrated over elevation bands of 100 m between 2013 and 2020 are used for calibration. A comparison with WGMS data for the second half of the 20th century is performed for Kara-Batkak glacier. The cumulative mass balances are also compared with geodetic mass balances reconstructed for different time periods. Generally, we find a close agreement, indicating a high confidence in the created mass balance series. The last 20 years show a negative mean specific mass balance except for 2008–2009 when a slightly positive mass balance was found. This indicates that the glaciers are currently in imbalance with the present climatic conditions in the area. For the reconstruction back to 1750, this study specifically highlights that it is essential to adapt the glacier geometry since the end of the Little Ice Age in order to not over- or underestimate the mean specific mass balance. The datasets created can be used to get a better insight into how climate change affects glaciers in the Inner Tien Shan and to model the future evolution of these glaciers as well as other glaciers in the region.

Reconstructed Centennial Mass Balance Change for Golubin Glacier, Northern Tien Shan

“…Similarly, their results suggest more positive mass balance at the beginning of the 20th century followed by increasingly negative mass balances, especially from the 1970s onward. In contrast with the here present study, Van Tricht et al [43] adjusted not only the glacier area but also the thickness over the study period. They showed that initial geometry and considerations for the glacier retreat had a strong influence on glacier mass balance.…”

“…100 −1 m from 1985 to 1989 [42]. Van Tricht et al [43] found the average mass balance gradient from the Little Ice Age to present to span from 0.50 and 0.60 m w.e. 100 −1 m for glaciers Karabatkak, Sary-Tor, and Bordu.…”

“…Van Tricht et al [43] reconstructed the mean specific mass balance of Bordu, Kara-Batkak, and Sary-Tor by using a strongly parameterized surface energy mass balance model from 1750 until present. Similarly, their results suggest more positive mass balance at the beginning of the 20th century followed by increasingly negative mass balances, especially from the 1970s onward.…”

“…yr −1 from 1967/1968 to 1997/ 1998 and −0.20 m w.e. yr −1 from 2011/12 to 2019/2020 [25].Van Tricht et al[43] reconstructed the mean specific mass balance of Bordu, Kara-Batkak, and Sary-Tor by using a strongly parameterized surface energy mass balance model from 1750 until present. Similarly, their results suggest more positive mass balance at the…”

Modelling runoff components and hydrological processes in glaciated catchments of the inner Tien-Shan, Kyrgyzstan

“…and 0.6 m w.e. yr -1 per 100 m (van Tricht et al, 2021), in the ablation zone of glacier No.354 it was estimated as 0.68 m w.e. yr -1 per 100 m (Kronenberg et al, 2016) and for south-faced Grigoriev glacier it was 0.6 m w.e.…”