English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

doi: 10.7185/geochemlet.2013 Global warming is adversely affecting the melting rates of Himalayan glaciers, which feed a number of large river systems in the Indian sub-continent. Regional scale assessment of glaciers and their link to rivers are mostly quantified using remote sensing data and modelling techniques. Here we present an alternative stable water isotope modelling approach. New oxygen and hydrogen isotopes (18O/16O and 2H/1H, expressed as δ18O and δD) data from the headwater of Indus River were analysed with a comprehensively compiled δ18O and δD dataset of Himalayan rivers to quantify the volumetric flow of glacier ice meltwater in the headwaters of the rivers Indus, Ganges, and Brahmaputra. The isotope mixing model reveals that the discharge weighted annual average glacier ice meltwater contribution in headwaters (>2000 m) of the Indus, the Ganges, and the Brahmaputra are 47 ± 13 %, 44 ± 13 %, and 29 ± 10 %, respectively, which corresponds to a minimum of 33.5 ± 6.5 Gt yr-1 of melted ice mass. Our results show that annual glacier ice meltwater contributions vary across the river basins, with Indus River receiving the highest contribution. We conclude that stable water isotope modelling is an alternative approach to study regional scale glacier-river interactions to address the future impact of climate change over glaciated Himalayan catchments. Received 4 September 2019 | Accepted 6 March 2020 | Published 16 April 2020 1. Department of Earth Sciences, Indian Institute of Technology Kanpur, UP 208016, India * Corresponding author (email: soumita@iitk.ac.in) Introduction The glaciated region over the Himalaya and surrounding, the third largest on Earth and referred to as the “Third Pole”, feeds many large river systems including the Indus, the Ganges, the Brahmaputra, the Salween, the Mekong, and the Yangtze (Fig. S-1). Over the past decade, it has become clear that the Himalayan glaciers are shrinking (Bolch et al., 2012; Shrestha et al., 2015) raising questions about their ability to sustain the freshwater supply that meets the demands of 800 million people in SE Asia. The concern is particularly significant during the drought years, as melted glacier ice, hereafter referred to as “ice meltwater” is considered a drought resilient water source (Shrestha et al., 2015). To understand glacier sustainability, attempts have been made to quantify the annual glacial mass loss mostly using remote sensing data and related modelling techniques (Cogley, 2012) such as airborne and satellite laser altimetry (Jacob et al., 2012; Kääb et al., 2012), space gravimetry using data from Gravity Recovery and Climate Experiment (GRACE), Ice, Cloud, and land Elevation Satellite (ICESat) missions (Gardner et al., 2013), and digital elevation models (Gardelle et al., 2013). While these estimates provide important insight into the glacial mass loss problem, they have a considerable disagreement (Table S-1). Moreover, remote sensing glacier mass loss estimation takes into account both mass gain (accumulation) and mass loss (ablation) in a balance year, and this net loss estimate cannot be directly converted to volumetric ice meltwater flow in rivers. For example, a glacier releasing as much ice meltwater during summer as it gains through the accumulation of snow during winter will be at a zero net mass loss, although, the glacier might have released a substantial amount of ice meltwater to the river network. Therefore, we need to quantify the total ice mass loss (just the ablation) to understand better the glacier-river linkages and to assess further the impact of ice meltwater on downstream ecosystem services. To understand the snow meltwater and the ice meltwater contribution to Himalayan rivers, we additionally rely on various cryospheric-hydrological models (Kaser et al., 2010; Lutz et al., 2014). However, hydrological modelling derived estimates of source end member contributions to the Himalayan rivers show considerable disagreement and it is also difficult to compare the results from different studies due to lack of homogeneity in the consideration of source end members (Table S-2). Therefore, there is a clear need to develop new techniques that could quantify the water source end member contributions to streamflow and determine the river dependence on the non-renewable source, the glacier ice. Additionally, it would help to understand the limitations of different approaches and improve our understanding of the regional scale basin hydrology.

Tracing ‘Third Pole’ ice meltwater contribution to the Himalayan rivers using oxygen and hydrogen isotopes