Quantifying Overestimated Permafrost Extent Driven by Rock Glacier Inventory

Cao, Bin; Li, Xiaoqiong; Feng, Min; Zheng, Donghai

doi:10.1029/2021gl092476

Cited by 10 publications

(5 citation statements)

References 47 publications

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“…Active rock glaciers contain a perennially frozen mixture of debris (Brardinoni et al, 2019; Haeberli, 1985); therefore, intact rock glaciers are thought to be visible indicators of the presence/absence of permafrost (Haeberli et al, 2006), with some degree of uncertainty (Cao et al, 2021). Despite the limitations and uncertainties associated with the geomorphological categories, this classification scheme has been essentially adopted to assess the permafrost probability distribution in earlier studies, especially in the data‐scarce regions of HKH (Baral et al, 2020; Haq & Baral, 2019; Hassan et al, 2021; Kääb et al, 2021; Schmid et al, 2015), and it has also been adopted in other regions (Sattler et al, 2016; Scotti et al, 2013).…”

Section: Methodsmentioning

confidence: 99%

Rock glacier distribution and kinematics in Shigar and Shayok basins based on radar and optical remote sensing

Hassan,

Berg,

Lippert

et al. 2024

Earth Surf Processes Landf

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Recent studies have demonstrated the rock glacier destabilisation and permafrost thawing induced by warming climate represent a continuous threat to life, infrastructure and socio‐economic development in the mountainous regions of the Hindu Kush Himalaya. This study presents the first systematic rock glacier inventory for the Shigar and Shayok basins, quantifying rock glacier geomorphology and kinematics based on morphological evidence using Google Earth images and interferometric synthetic aperture radar (InSAR). The certainty index of each inventoried rock glacier is recorded, along with its geomorphological properties and kinematic attributes. The rock glacier velocity is estimated through the InSAR time series analysis of Sentinel‐1 images from 2020 to 2021, with temporal baselines at 12‐day intervals. We developed a rock glacier inventory consisting of 84 rock glaciers covering an area of 29 km2 for the Shigar Basin and 2206 rock glaciers encompassing 369 km2 for the Shayok Basin. Among these rock glaciers, 69% and 52% are categorised as active rock glaciers, respectively. Rock glaciers in both catchments are confined to elevations between 3600 and 5875 m a.s.l., with a mean area of 0.22 km2. The maximum recorded velocity for active rock glaciers in the Shigar Basin is 101 ± 9 cm year−1, with a median of 27 ± 10 cm year−1, and in the Shayok Basin 114 ± 10 cm year−1 (median of 29 ± 9 cm year−1). Temporal variations in the surface velocities of the rock glaciers reveal that they increase with rising temperatures in both catchments, highlighting the seasonality in the rock glacier surface velocity. In total, we recorded the kinematic attributes of 98% of the inventoried rock glaciers in the study area.

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Section: Methodsmentioning

confidence: 99%

Rock glacier distribution and kinematics in Shigar and Shayok basins based on radar and optical remote sensing

Hassan,

Berg,

Lippert

et al. 2024

Earth Surf Processes Landf

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“…However, the permafrost extent is approximately ten times larger than the glacierized area [257]. It is well known that the permafrost extent was overestimated by the approaches using rock glaciers as a proxy due to the ground-cooling effects of rock glaciers [258].…”

Section: Permafrost Hydrological Modelingmentioning

confidence: 99%

Remote Sensing and Modeling of the Cryosphere in High Mountain Asia: A Multidisciplinary Review

Ye,

Wang,

Liu

et al. 2024

Remote Sensing

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Over the past decades, the cryosphere has changed significantly in High Mountain Asia (HMA), leading to multiple natural hazards such as rock–ice avalanches, glacier collapse, debris flows, landslides, and glacial lake outburst floods (GLOFs). Monitoring cryosphere change and evaluating its hydrological effects are essential for studying climate change, the hydrological cycle, water resource management, and natural disaster mitigation and prevention. However, knowledge gaps, data uncertainties, and other substantial challenges limit comprehensive research in climate–cryosphere–hydrology–hazard systems. To address this, we provide an up-to-date, comprehensive, multidisciplinary review of remote sensing techniques in cryosphere studies, demonstrating primary methodologies for delineating glaciers and measuring geodetic glacier mass balance change, glacier thickness, glacier motion or ice velocity, snow extent and water equivalent, frozen ground or frozen soil, lake ice, and glacier-related hazards. The principal results and data achievements are summarized, including URL links for available products and related data platforms. We then describe the main challenges for cryosphere monitoring using satellite-based datasets. Among these challenges, the most significant limitations in accurate data inversion from remotely sensed data are attributed to the high uncertainties and inconsistent estimations due to rough terrain, the various techniques employed, data variability across the same regions (e.g., glacier mass balance change, snow depth retrieval, and the active layer thickness of frozen ground), and poor-quality optical images due to cloudy weather. The paucity of ground observations and validations with few long-term, continuous datasets also limits the utilization of satellite-based cryosphere studies and large-scale hydrological models. Lastly, we address potential breakthroughs in future studies, i.e., (1) outlining debris-covered glacier margins explicitly involving glacier areas in rough mountain shadows, (2) developing highly accurate snow depth retrieval methods by establishing a microwave emission model of snowpack in mountainous regions, (3) advancing techniques for subsurface complex freeze–thaw process observations from space, (4) filling knowledge gaps on scattering mechanisms varying with surface features (e.g., lake ice thickness and varying snow features on lake ice), and (5) improving and cross-verifying the data retrieval accuracy by combining different remote sensing techniques and physical models using machine learning methods and assimilation of multiple high-temporal-resolution datasets from multiple platforms. This comprehensive, multidisciplinary review highlights cryospheric studies incorporating spaceborne observations and hydrological models from diversified techniques/methodologies (e.g., multi-spectral optical data with thermal bands, SAR, InSAR, passive microwave, and altimetry), providing a valuable reference for what scientists have achieved in cryosphere change research and its hydrological effects on the Third Pole.

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“…As limited field-based evidence exists, rock glaciers are often considered as visual indicators of, and ground-truth data for the occurrence of permafrost in the HKH (Haq & Baral, 2019;Hassan et al, 2021;Khan et al, 2021;Pandey, 2019). This could, however, lead to overestimations of the extent of permafrost because rock glaciers generally represent more suitable premises for the existence of permafrost compared to adjoining ground (Cao et al, 2021).…”

Section: Permafrostmentioning

confidence: 99%

Chapter 2: Consequences of climate change for the cryosphere in the Hindu Kush Himalaya

Jackson¹,

Azam²,

Baral³

et al. 2023

Water, Ice, Society, and Ecosystems in the Hindu Kush Himalaya: An Outlook

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Chapter 2 of the Water, ice, society, and ecosystems in the HKH (HI-WISE) assessment report provides an overview of the changing climate in the Hindu Kush Himalayan (HKH) region and the observed and projected impacts on the HKH cryosphere. The HKH glaciers are projected to lose 30%–50% of their volume by 2100 even if global warming remains below 2°C. Snow cover is projected to fall by up to a quarter under high emissions scenarios – drastically reducing freshwater for major rivers. Chapter 2 finds that glacier mass loss has accelerated by 65% in the region, rising from –0.17 to –0.28m per year water equivalent loss in the decades starting 2000 and 2010. The Karokoram Anomaly has ended.   The effects of the changing cryosphere on fragile mountain habitats are projected to be acute, with cascading impacts and disasters reported in most ecosystems and affecting most inhabitant species.

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Quantifying Overestimated Permafrost Extent Driven by Rock Glacier Inventory

Cited by 10 publications

References 47 publications

Rock glacier distribution and kinematics in Shigar and Shayok basins based on radar and optical remote sensing

Rock glacier distribution and kinematics in Shigar and Shayok basins based on radar and optical remote sensing

Remote Sensing and Modeling of the Cryosphere in High Mountain Asia: A Multidisciplinary Review

Chapter 2: Consequences of climate change for the cryosphere in the Hindu Kush Himalaya

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