On the strongly imbalanced state of glaciers in the Sikkim, eastern Himalaya, India

Garg, Purushottam Kumar; Shukla, Aparna; Jasrotia, Avtar Singh

doi:10.1016/j.scitotenv.2019.07.086

Cited by 47 publications

(34 citation statements)

References 73 publications

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“…2008; Garg et al . 2019). Based on the known different controlling factors, we suggest that differences in the chronology may be due to the morphology or slope of the glacier (Chenet et al .…”

Section: Discussionmentioning

confidence: 99%

Evidence of the largest Late Holocene mountain glacier extent in southern and southeastern Greenland during the middle Neoglacial from ¹⁰Be moraine dating

Biette

Jomelli

Chenet

et al. 2021

Boreas

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The timing of mountain glacier fluctuations is poorly constrained in some parts of Greenland during the Late Holocene. We present 31 10Be cosmic‐ray exposure ages (CRE) of boulders collected from three mountain glacier moraines located in the Tasilap valley, in southeastern Greenland, and 10 10Be CRE ages from one mountain glacier in the Isortup valley, in southern Greenland. For the first time in these areas, mountain glacier fluctuations are documented from moraine CRE for the Late Holocene period. Several glacier advances during the Late Holocene are revealed with exposure ages ranging from 3.90±0.26 to 0.4±0.04 ka. Moraines of three of the four glaciers investigated, dated to 3.75±0.13 ka (n = 3), 3.3±0.19 ka (n = 2) and 2.87±0.13 ka (n = 3), show a common timing of the largest glacier expansion during the Late Holocene. Evidence of at least one individual moraine deposited at ~1.2 ka was found on all glaciers. Finally, the most recent period of glacial advance during the Late Holocene is documented by one glacier in each valley at ~0.66–0.70 ka. The maximum glacier extent at ~3 ka differs from the Late Holocene glacier maximum extent usually reported during the Little Ice Age in east Greenland based on moraine dating and lake sediments. We suggest that the combination of a stronger East Greenland Current and a weaker Irminger Current, potentially associated with increased sea‐ice concentration, superimposed on the long‐term decrease in summer insolation during the Late Holocene could be responsible for this large glacial advance at ~3 ka in southern and southeastern Greenland.

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Section: Discussionmentioning

confidence: 99%

Evidence of the largest Late Holocene mountain glacier extent in southern and southeastern Greenland during the middle Neoglacial from ¹⁰Be moraine dating

Biette

Jomelli

Chenet

et al. 2021

Boreas

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“…However, due to global warming, global glaciers are showing a trend of retreat and thinning. Recent studies on mass balance (Rowan et al, 2015;Lynch et al, 2016;Dehecq et al, 2018;Wu et al, 2018;Wang et al, 2019a;Wouters et al, 2019;Zemp et al, 2019), glacial area change (Paul et al, 2013;Patel et al, 2019;Reinthaler et al, 2019), surface velocity (Wang et al, 2018;Altena et al, 2019;Garg et al, 2019), glacio-hydrological modeling (Shrestha et al, 2015), and glaciers' response to climate change (Scherler et al, 2011;Rowan et al, 2015) have revealed that changes in glaciers are exerting an impact on socioeconomic development in their downstream areas through changes in glacial water resources in High Mountain Asia (Immerzeel et al, 2010). Climate change may force geomorphological processes on high mountain slopes (Tipper et al, 2012;Cook et al, 2020) by accelerating the disintegration of rocks and increasing the accumulation of debris on glaciers and mountain slopes.…”

Section: Introductionmentioning

confidence: 99%

Upward Expansion of Supra-Glacial Debris Cover in the Hunza Valley, Karakoram, During 1990 ∼ 2019

Xie

Liu

et al. 2020

Front. Earth Sci.

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Supra-glacial debris cover is key to glacier ablation through increasing (thin debris layer) or decreasing (thick debris layer) melt rates, thereby regulating the mass balance of a glacier and its meltwater runoff. The thickening or lateral expansion of supra-glacial debris cover correlates with a reduction of glacier ablation and, consequently, runoff generation, which is also considered to be an influential factor on the rheology and dynamics of a glacierized system. Studies on supra-glacial debris cover have recently attracted wide attention especially for glaciers in the Himalayas and Karakoram, where the glaciers have heterogeneously responded to climate change. In this study, we used 32 images from the Landsat Thematic Mapper, Enhanced Thematic Mapper Plus, and Operational Land Imager archive, going back to 1990, which are available on the Google Earth Engine cloud-computing platform, to map the supra-glacial debris cover in the Hunza Valley, Karakoram, Pakistan, based on a band ratio segmentation method (normalized difference snow index [NDSI] < 0.4), Otsu thresholding, and machine learning algorithms. Compared with manual digitization, the random forest (RF) model was found to have the greatest accuracy in identifying supra-glacial debris, with a Kappa coefficient of 0.94 ± 0.01 and an overall accuracy of 95.5 ± 0.9%. Overall, the supraglacial debris cover in the study area showed an increasing trend, and the total area expanded by 8.1-21.3% for various glaciers from 1990 to 2019. The other two methods (Otsu thresholding and NDSI < 0.4) generally overestimated the supra-glacial debris covered area, by 36.3 and 18.8%, respectively, compared to that of the RF model. The supra-glacial debris cover has migrated upward on the glaciers, with intensive variation near the equilibrium-line altitude zone (4,500-5,500 m a.s.l.). The increase in ice or snow avalanche activity at high altitudes may be responsible for this upward expansion of supra-glacial debris cover in the Hunza Valley, which is attributed to the combined effect of temperature decrease and precipitation increase in the study area.

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“…This area change when estimated for a duration of 23 years resulted into a mean area loss of 13.69% underlining the higher glacier area loss in section‐3. An analysis of glacier change studies over glaciers of sections‐2a and 2b for a period of 21 years (1994–2015) resulted into mean glacial area loss values of 2.55 and 3.08% when estimated for 23 years (Garg et al ., 2019). These values are comparable to those obtained in the current study at 4.84 and 6.57% for sections‐2a and 2b, respectively.…”

Section: Discussionmentioning

confidence: 99%

Topoclimatic zones and characteristics of the upper Ganga basin, Uttarakhand, India

Yadav

Thayyen

Jain

2020

Intl Journal of Climatology

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The upper Ganga basin (UGB) constituting Bhagirathi and Alakananda basins has been considered as a single hydrological unit so far with comparable climate forcing. Here, we show three distinct “topoclimatic zones” of this basin having characteristically different temperature, precipitation, and orographic processes. The orographic discontinuity forced by a mountain ridge with an average elevation of 5,200 m a.s.l. is instrumental in the development of these topoclimatic zones. The northern region of the basin is identified as high elevation and high temperature zone (HE‐HT) with monsoon moisture deficit. This monsoon deficit region is characterized by higher land surface temperature lapse rate (LSTLR) during July and August (JA) derived from MODIS‐LST (11.00°C/km) as compared to much lower LSTLR of monsoon topoclimatic zone (5.78°C/km). The nival‐glacier regimes of the monsoon dominant and monsoon deficit regions constituted the third topoclimatic zone characterized by high elevation‐low temperature zone (HE‐LT). This zone has comparatively lower temperature lapse rate (5.26°C/km) than the immediately lower elevations. The coldest points identified in the basin are mostly placed in monsoon deficit regions with higher LSTLR. The 10–12°C isotherm in the monsoon deficit zone runs at 5,300 m a.s.l. as compared to 3,200 m a.s.l. in monsoon dominant zone. It is proposed that 80% of glacier area in the UGB is in the monsoon deficit zone that is regulated by the northern region orographic processes rather than southern slopes. Glacier change in the southern and northern zones show significant difference during the period of 1994–2016/2017, with significantly higher glacier area loss in the HE‐HT zone. The study highlights the importance of these topoclimatic considerations while evaluating the climate and hydrology of UGB.

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On the strongly imbalanced state of glaciers in the Sikkim, eastern Himalaya, India

Cited by 47 publications

References 73 publications

Evidence of the largest Late Holocene mountain glacier extent in southern and southeastern Greenland during the middle Neoglacial from ¹⁰Be moraine dating

Evidence of the largest Late Holocene mountain glacier extent in southern and southeastern Greenland during the middle Neoglacial from ¹⁰Be moraine dating

Upward Expansion of Supra-Glacial Debris Cover in the Hunza Valley, Karakoram, During 1990 ∼ 2019

Topoclimatic zones and characteristics of the upper Ganga basin, Uttarakhand, India

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On the strongly imbalanced state of glaciers in the Sikkim, eastern Himalaya, India

Cited by 47 publications

References 73 publications

Evidence of the largest Late Holocene mountain glacier extent in southern and southeastern Greenland during the middle Neoglacial from 10Be moraine dating

Evidence of the largest Late Holocene mountain glacier extent in southern and southeastern Greenland during the middle Neoglacial from 10Be moraine dating

Upward Expansion of Supra-Glacial Debris Cover in the Hunza Valley, Karakoram, During 1990 ∼ 2019

Topoclimatic zones and characteristics of the upper Ganga basin, Uttarakhand, India

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Evidence of the largest Late Holocene mountain glacier extent in southern and southeastern Greenland during the middle Neoglacial from ¹⁰Be moraine dating

Evidence of the largest Late Holocene mountain glacier extent in southern and southeastern Greenland during the middle Neoglacial from ¹⁰Be moraine dating