Glaciers are the principal supply of freshwater in frigid locations and are critical for the water resources of billions of people, notably in High Mountain Asia (HMA) (Jones et al., 2019; Mohammadi et al., 2023; Nüsser & Schmidt, 2021; Rounce et al., 2023). Glaciers are key indicators of climate change (Kääb et al., 2007; Kaushik et al., 2022; Lama & Devkota, 2009), and the Himalayan region is one of the few regions where climate change effects are most prominent (Negi et al., 2021; Wester et al., 2019). Global warming poses a threat to glaciers (Compagno et al., 2022; Immerzeel et al., 2010) resulting rapid retreat globally (Shean et al., 2020), while warming reported in the Himalayan region is higher than the global mean warming (Bhutiyani et al., 2007; Negi et al., 2018; Shrestha et al., 2012), causing glaciers to lose mass at a faster pace (Nie et al., 2021; Sabin et al., 2020; Sharma et al., 2022). Although some advancing glaciers were observed in the Karakoram Mountains during the first decade of the twenty-first century but retreating rates differed greatly amongst glacial basins (Dehecq et al., 2019).
Glacier retreat causes melt water to collect as glacial lakes (Allen et al., 2016; Carrivick & Tweed, 2013; Lei et al., 2018), glacial lakes are also formed in glacier valleys and basins due to melting ice (Bajracharya & Mool, 2009; Muhammad et al., 2021) resulting in more melt and retreat and more lake expansion (King et al., 2019; Maurer et al., 2019; Watson et al., 2020). Outburst floods from glacial lakes pose a severe risk to infrastructure and humans (Allen et al. 2015). The physical condition of the lake, dam, source glacier activity, and surrounding stability all contribute to its resilience (Bajracharya et al. 2020). These lakes are frequently blocked by unstable moraine or glacier ice, and they are flanked by destabilizing permafrost slopes or hanging glaciers (Otto, 2019; Richardson and Reynolds, 2000). Slope failure can cause mass movement, displacing water and creating an impulse wave that overtops the frontal dam (Ambruster et al. 1978). Lake expansion raises the likelihood of overtopping failures and consequent flood volume, contributing to increased GLOF hazard (Bajracharya & Mool, 2009; Muhammad et al., 2021; Muhammad et al., 2020; Tian et al., 2017; Zhang et al., 2015). Moraine-dammed lakes are prevalent, consisting of loose, coarse moraines with low cementing content, makes them vulnerable to GLOFs, making them easy to erode. GLOFs can be caused by dam breach (Emmer & Cochachin, 2013; Rounce et al., 2016), overfilling (Allen et al., 2016a), and moraine/ice dam degradation (Majeed et al., 2021; Neupane et al., 2019), making it difficult to accurately quantify (Taylor et al., 2023), triggering is complex and can cause significant damage to property, infrastructure, and agricultural land, resulting in extensive loss of life (Carey, 2008; Emmer et al., 2020). The expansion of these lakes perils locale (Grant et al., 2021) due to GLOFs risk intensification (Frey et al., 2012; Shugar et al., 2020; Wang et al., 2021; Wieczorek et al., 2022).
Flooding increases turbidity, while surface signatures effect river landscapes (Meena et al., 2021). The Jinweng Co GLOF event in 2020 destroyed ten houses, bridges, and 43.9 km of road, causing damage to structures and agricultural land (Zheng et al. 2021). In 2013, a Chorabari lake debris flow and cloud-burst-induced landslides in Uttarakhand caused over 6,000 deaths and infrastructure damage (Allen et al. 2015). A catastrophic flood in the Rishiganga River occurred on 7 February 2021 due to a rockslide (Mao et al., 2022; Meena et al., 2021; Pandey et al., 2022), causing displaced materials, solar radiation, and glacier collapse, destroying infrastructure and lives (Pandey et al., 2022). Rising temperature may cause similar incidents in Himalayan valley (Pandey et al., 2022). Uncertainty exists on glacier lake evolution trends and future development over recent decades (Kumar et al., 2020). Remote sensing risk assessment aids in identifying flood hotspots in South Asia (Matheswaran et al., 2019). (Muhammad et al., 2021) predicted Shisper lake outburst due to terminus advances, lake developed a GLOF event in 2022. Shisper Glacier surges from 2017 to 2019 blocked Mochowar Glacier's tributary, forming an ice dammed lake, leading to GLOFs in 2019, 2020, and 2022 (Singh et al. 2023).
GLOF risk is highest in Himalaya, with potential to triple in future (Zheng et al., 2021) resulting in floods and scarce water resources that are of societal and ecological importance (Shugar et al., 2020). The impact varies significantly across the globe, requires urgent attention to reduce its impacts (Dubey & Goyal, 2020; Shugar et al., 2020).
Glaciers with steep slopes and lower altitude range lose more area (Pandey & Venkataraman, 2013). Temperature significantly impacts glacier melt (Bajracharya et al. 2020;Schmidt & Nüsser, 2009)). Increasing glacial retreat caused by climate change, results in glacial lakes growth and bursts (Nautiyal et al., 2022). Recent environmental and climatic disturbances impacts land surface temperature, which is the radiating temperature of the earth's surface (Yuan & Bauer, 2007). LST and air temperature are closely associated (Hachem et al., 2012; Vancutsem et al., 2010) may fluctuate by 1–2°C under cloud cover causing an increase in warming (Good et al., 2017). Previous studies have used LST to assess risks (Crago et al., 1995; Hu & Brunsell, 2013; Weng & Fu, 2014). Glacial lakes have grown rapidly since 1990, increasing by ~ 50% globally (Shugar et al., 2020). Climate change in Himalaya is causing an increase in glacial lakes, warming and discharge at high elevation, which could lead to increased flood events and reduced low flows (Chalise et al., 2006). The dearth of a long-term decadal inventory of glacial lakes with inter-annual assessment in Northern Pakistan can be attributed to various factors. The advancements in spatial and temporal resolution have led to a significant transformation in the evaluation of mountain hazards through remote sensing (Deschamps-Berger et al., 2020; Huggel et al., 2002).
This paper focuses on the seasonal variability and decadal oscillations of glacial lakes in the Astore Basin in Northern Pakistan's western Himalayan range. The study examined the growth and changes in the basin's glacial lakes using multi-temporal satellite imagery Astore station climate data 1961–2021, third pole high resolution meteorological data by (He et al., 2020; Jiang et al., 2023) from 1979–2020 and MODIS LST data from 2010–2021. Climate data shows an increasing trend for temperature, LST, and decreasing precipitation, affecting glacial lakes in the region. Our results showed a consistent increase in the number and size of glacier lakes from June to September annually, as well as over the decadal period spanning from September 2001 to September 2014 to October 2021. Climatic fluctuations and LST enhancements are the key influencers causing rapid escalation in glacial lakes number and area. These findings demonstrate the utility of our two-way method for studying the evolution of glacier lakes and highlight the importance of monitoring these lakes to better understand the impacts of climate change on water resources.