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

Abstract

Abstract. The glacier mass balance is an important variable to describe the climate system and is used for various applications like water resource management or runoff modelling. The direct or glaciological method and the geodetic method are the standard methods to quantify glacier mass changes, and both methods are an integral part of international glacier monitoring strategies. In 2011, we established two glacier mass-balance programmes on Yala and Rikha Samba glaciers in the Nepal Himalaya. Here we present the methods and data of the directly measured annual mass balances for the first six mass-balance years for both glaciers from 2011/2012 to 2016/2017. For Yala Glacier we additionally present the directly measured seasonal mass balance from 2011 to 2017, as well as the mass balance from 2000 to 2012 obtained with the geodetic method. In addition, we analysed glacier length changes for both glaciers. The directly measured average annual mass-balance rates of Yala and Rikha Samba glaciers are −0.80 ± 0.28 and −0.39 ± 0.32 m w.e. a−1, respectively, from 2011 to 2017. The geodetically measured annual mass-balance rate of Yala Glacier based on digital elevation models from 2000 and 2012 is −0.74 ± 0.53 m w.e. The cumulative mass loss for the period 2011 to 2017 for Yala and Rikha Samba glaciers is −4.80 ± 0.69 and −2.34 ± 0.79 m w.e., respectively. The mass loss on Yala Glacier from 2000 to 2012 is −8.92 ± 6.33 m w.e. The winter balance of Yala Glacier is positive, and the summer balance is negative in every investigated year. The summer balance determines the annual balance. Compared to regional mean geodetic mass-balance rates in the Nepalese Himalaya, the mean mass-balance rate of Rikha Samba Glacier is in a similar range, and the mean mass-balance rate of Yala Glacier is more negative because of the small and low-lying accumulation area. During the study period, a change of Yala Glacier's surface topography has been observed with glacier thinning and downwasting. The retreat rates of Rikha Samba Glacier are higher than for Yala Glacier. From 1989 to 2013, Rikha Samba Glacier retreated 431 m (−18.0 m a−1), and from 1974 to 2016 Yala Glacier retreated 346 m (−8.2 m a−1). The data of the annual and seasonal mass balances, point mass balance, geodetic mass balance, and length changes are accessible from the World Glacier Monitoring Service (WGMS, 2021), https://doi.org/10.5904/wgms-fog-2021-05.

Multi-decadal monsoon characteristics and glacier response in High Mountain Asia

“…In contrast to this, the small Nepalese glacier (Yala) was much less sensitive to the wetter conditions at the start of the Millennium, resulting in a more continuous mass loss (figure 3), consistent with modelled long term mass balances in northwestern Nepal (Arndt et al 2021). Although the size of the glacier and its limited accumulation area (Stumm et al 2021, Sunako et al 2020 may have dictated its reduced sensitivity to the expansion of the monsoon period, an early monsoon actually produces less snowfall during the monsoon transition period (May-June) at this glacier, despite shifting the occurrence of snow sooner. A weakening monsoon intensity and drier conditions, coinciding with warmer air temperatures of recent decades (figure 2) can explain half of the mass balance variability at this glacier, but the amount of snowfall during late June is also of great importance (figure 6).…”

“…Yala Glacier (28.237 • N 85.619 • E) is a small, 1.5 km 2 glacier situated in Langtang Valley, Nepal which has been the subject of long-term mass balance campaigns (e.g. Fujita et al 1998, Baral et al 2014, Stumm et al 2021, Sunako et al 2020 as well as the focus of research on energy balance and surface processes (Stigter et al 2018, Litt et al 2019. Parlung Glacier Number 4 (29.245 • N 96.928 • E, hereafter 'Parlung 4' or 'PAR4') is a 11.7 km 2 , spring-type accumulation glacier in the southeastern Tibetan Plateau.…”

Up-glacier propagation of surface lowering of Yala Glacier, Langtang Valley, Nepal Himalaya

“…Fujita and Nuimura, 2011; Sugiyama and others, 2013). Acharya and Kayastha (2019) conducted in situ mass balance measurements for the 2011–2017 period, and Stumm and others (2021) updated a mass loss value of −0.80 ± 0.28 m water equivalent (w.e.) a −1 , with a mean equilibrium line altitude of 5456 m a.s.l.…”

“…However, in situ observational studies remain scarce due to the remoteness of these glaciers and the associated logistical difficulties (e.g. Yao and others, 2012; Azam and others, 2016; Sherpa and others, 2017; Sunako and others, 2019; Angchuk and others, 2021; Stumm and others, 2021). Previous studies have employed global positioning system (GPS) and/or rangefinders during repeated surveys to derive point-based DEMs and capture surface elevation changes, and therefore estimate geodetic glacier mass balances (e.g.…”

Positive mass budgets of high-altitude and debris-covered fragmented tributary glaciers in Gangotri Glacier System, Himalaya

“…In situ glacier-wide mass balance (MB) monitoring of glaciers provides an understanding of the quick response of the glaciers to local meteorological conditions (Oerlemans, 2001). Several in situ glaciological studies are being conducted over the different basins of the Himalaya (Dobhal et al, 2013;Mandal et al, 2020;Wagnon et al, 2021;Stumm et al, 2021) but these observations are still sparser compared to the other glacierized regions of the world (Zemp et al, 2015;Azam et al, 2018). Due to the harsh climatic conditions, low oxygen level, and steep terrain of the Himalaya, the in situ MBs have only been observed for a short period and on a few small glaciers (Azam et al, 2018).…”