Mass balances of Yala and Rikha Samba Glacier, Nepal from 2000 to 2017

Abstract. The direct or glaciological method is an integral part of international glacier monitoring strategies, and the mass balance is an essential variable to describe the climate system and model runoff. In 2011, we established two glacier mass balance programmes on Yala and Rikha Samba Glacier in the Nepal Himalaya. Here we present the methods and data that we ingested into the database of the World Glacier Monitoring Service. We present glacier length changes and the annual mass balances for the first six mass balance years for both glaciers. For Yala Glacier we additionally present the mass balance of seasonal in situ measurements and the mass balance from 2000 to 2012 analysed with the geodetic method. The annual mass balance rates of Yala Glacier from 2000 to 2012 and from 2011 to 2017 are −0.74 ± 0.53 m and −0.74 ± 0.28 m w.e. a−1, and for Rikha Samba Glacier from 2011 to 2017 −0.39 ± 0.32 m w.e. a−1. The mass loss for the period 2011 to 2017 for Yala and Rikha Samba Glacier −4.44 ± 0.69 m w.e. and −2.34 ± 0.79 m w.e., respectively. The winter balance of Yala Glacier is positive in every investigated year, but the negative summer balance determines the annual balance. The mass balance of Yala Glacier is more negative than on other glaciers in the region, mostly because of the small and low lying accumulation area. The mass balance of Rikha Samba Glacier is more positive than the other glaciers in the region, likely because of the large and high lying accumulation area. Due to the topography, the retreat rates of Rikha Samba Glacier are much higher than for Yala Glacier. From 1989 to 2013, Rikha Samba retreated 431 m (−18.0 m a−1), and from 1974 to 2016 Yala Glacier retreated 346 m (−8.2 m a−1). During the study period, a change of Yala Glacier's surface topography has been observed with glacier thinning and down wasting, which indicates the likely disappearance of Yala Glacier within this century. The datasets are freely accessible from WGMS (2020a): Fluctuations of Glaciers Database. World Glacier Monitoring Service, Zurich, Switzerland. http://dx.doi.org/10.5904/wgms-fog-2020-08.