Contrasting thinning patterns between lake- and land-terminating glaciers in the Bhutanese Himalaya

Tsutaki, Shun; Fujita, Koji; Nuimura, T.; Sakai, Akiko; Sugiyama, Shin; Komori, Jiro; Tshering, Phuntsho

doi:10.5194/tc-13-2733-2019

Cited by 47 publications

(92 citation statements)

References 78 publications

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“…Sustained glacier recession is driving the development of proglacial lakes at the termini of glaciers as meltwater accumulates within bedrock basins, behind moraine ridges and outwash fan heads, or is impounded by dead ice (Carrivick & Tweed, 2013). Glaciers in contact with a lake are receding more rapidly than their land‐terminating counterparts, for example, in the Himalaya (Maurer et al, 2019; Tsutaki et al, 2019), in Alaska (Larsen et al, 2007; Willis et al, 2012), and in New Zealand (Chinn et al, 2012). Glaciers terminating in proglacial lakes can lose mass by several mechanisms in addition to melt from energy exchanges at the ice surface, namely, calving and subaqueous melting, collectively known as frontal ablation (Maurer et al, 2016; Sakai et al, 2009; Truffer & Motyka, 2016; Watson et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Proglacial Lakes Control Glacier Geometry and Behavior During Recession

Sutherland

Carrivick

Gandy

et al. 2020

Geophysical Research Letters

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Ice-contact proglacial lakes are generally absent from numerical model simulations of glacier evolution, and their effects on ice dynamics and on rates of deglaciation remain poorly quantified. Using the BISICLES ice flow model, we analyzed the effects of an ice-contact lake on the Pukaki Glacier, New Zealand, during recession from the Last Glacial Maximum. The ice-contact lake produced a maximum effect on grounding line recession >4 times further and on ice velocities up to 8 times faster, compared to simulations of a land-terminating glacier forced by the same climate. The lake contributed up to 82% of cumulative grounding line recession and 87% of ice velocity during the first 300 years of the simulations, but those values decreased to just 6% and 37%, respectively, after 5,000 years. Numerical models that ignore lake interactions will, therefore, misrepresent the rate of recession especially during the transition of a land-terminating to a lake-terminating environment. Plain Language Summary Lakes form at the margins of glaciers as meltwater accumulates against hillsides and behind ridges of glacier debris. Lakes at a glacier terminus are known to affect its behavior. However, glaciers terminating into such lakes are usually absent from computer simulations, and the effects of these lakes on the rates of deglaciation and on glacier behavior are poorly quantified. In this study, we tested the effect of a lake on glacier recession under two different scenarios; a land-terminating versus a lake-terminating glacier. We used an ice flow model called BISICLES and applied it to what was once the Pukaki Glacier in New Zealand during the end of the last ice age. We found that the presence of a lake caused the glacier to recede more than 4 times further and it accelerated ice flow by up to 8 times when compared to the same glacier that terminated on land under the same climate. Our simulated lake processes predominantly influenced the glacier over decades to centuries rather than over millennia. We suggest, therefore, that simulations of glacier evolution ignoring glacial lakes will likely misrepresent the timing and rate of recession, especially during the transition from a land-terminating to a lake-terminating environment. Recent observations, both field-based (e.g., Watson et al., 2020) and via satellite imagery (e.g., King et al., 2019), have highlighted the spatiotemporal frequency and magnitude of changes in glacial lakes and the associated glaciers that feed meltwater to them. However, field-based measurements are limited to

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Section: Introductionmentioning

confidence: 99%

Proglacial Lakes Control Glacier Geometry and Behavior During Recession

Sutherland

Carrivick

Gandy

et al. 2020

Geophysical Research Letters

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“…Dehecq et al (2019) documented widespread land-terminating glacier slowdown since the start of the 21 st century across High Mountain Asia (HMA) in response to diminished driving stress caused by long-term ice thinning. In contrast, more localised studies have shown several examples of lake-terminating glacier flow acceleration over a similar time period (King et al, 2018;Liu et al, 2020;Song et al, 2017;Tsutaki et al, 2019). The number and total area of proglacial lakes in the Himalayan region has increased (Nie et al, 2017;Shugar et al, 2020;Zhang et al, 2015), a trend which is likely to continue in the near future, as many glaciers are situated within overdeepenings (Linsbauer et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

“…Numerical ice-flow models have been utilised to investigate the dynamic thinning of marine-terminating outlet glaciers (Benn et al, 2007a;Enderlin et al, 2013;Nick & Oerlemans, 2006;Vieli et al, 2001;Vieli & Nick, 2011) and more recently of laketerminating glaciers in alpine regions (Sutherland et al, 2020;Tsutaki et al, 2019). Tsutaki et al (2019) employed a diagnostic 2-d model setup to show that the transition from a land to a lake-terminating boundary condition will significantly increase the surface flow velocities near the calving front. Sutherland et al (2020) used a numerical transient model setup to show that a proglacial lake was a dominant control on the ice velocity during times of glacial lake growth after the Last Glacial Maximum in New Zealand.…”

Section: Introductionmentioning

confidence: 99%

Proglacial Lakes Elevate Glacier Surface Velocities in the Himalayan Region

Pronk

Bolch

King

et al. 2021

Preprint

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Abstract. Meltwater from Himalayan glaciers sustains the flow of rivers such as the Ganges and Brahmaputra on which over half a billion people depend for day-to-day needs. Upstream areas are likely to be affected substantially by climate change, and changes in the magnitude and timing of meltwater supply are likely to occur in coming decades. About 10 % of the Himalayan glacier population terminates into pro-glacial lakes and such lake-terminating glaciers are known to exhibit higher than average total mass losses. However, relatively little is known about the mechanisms driving exacerbated ice loss from lake-terminating glaciers in the Himalaya. Here we examine a composite (2017–2019) glacier surface velocity dataset, derived from Sentinel 2 imagery, covering Central and Eastern Himalayan glaciers larger than 3 km2. We find that centre flow line velocities of lake-terminating glaciers are more than double those of land-terminating glaciers (18.8 vs 8.24 m yr−1) and show substantially more heterogeneity around glacier termini. We attribute this large heterogeneity to the varying influence of lakes on glacier dynamics, resulting in differential rates of dynamic thinning, which effects about half of the clean-ice lake-terminating glacier population. Numerical ice-flow model experiments show that changes at the frontal boundary condition are likely to play a key role in accelerating the glacier flow at the front, with variations in basal friction only being of modest importance. The expansion of current glacial lakes, and the formation of new meltwater bodies will influence the dynamics of an increasing number of Himalayan glaciers in the future; a scenario not currently considered in regional ice loss projections.

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“…In order to better understand the impact of proglacial lakes onto glacier dynamics and to find out whether the contribution of lake-terminating glaciers to Himalayan ice mass loss may increase further, more multi-decadal analysis on the glacier-lake dynamics, such as done by Liu et al (2020), is needed. Also there is an urgent call for more modeling studies on glacier-lake dynamics like Tsutaki et al (2019) and such studies should address problems of varying complexity such as glacier flow responds onto a reduction of effective pressure or changes in basin width, or higher-order models addressing the importance of the longitudinal stress gradient. Ultimately, comprehensive transient models are needed that couple lake development, glacier dynamics and calving fluxes to make better predictions of near future ice loss of Himalaya glaciers.…”

Section: Implications For Future Evolution Of Himalayan Glaciersmentioning

confidence: 99%

Proglacial Lakes Elevate Glacier Surface Velocities in the Himalayan Region

Pronk¹,

Bolch²,

King³

et al. 2021

Preprint

View full text Add to dashboard Cite

Meltwater from Himalayan glaciers sustains the flow of rivers such as the Ganges and Brahmaputra on which over half a billion people depend for day-to-day needs. Upstream areas are likely to be affected substantially by climate change, and changes in the magnitude and timing of meltwater supply are likely to occur in coming decades. About 10 % of the Himalayan glacier population terminates into pro-glacial lakes and such lake-terminating glaciers are known to be capable of accelerating total mass losses. However, relatively little is known about the mechanisms driving exacerbated ice loss from lake-terminating glaciers in the Himalaya. Here we examine a 2017-2019 glacier surface velocity dataset, derived from Sentinel 2 imagery, covering most of the Central and Eastern Himalayan glaciers larger than 3 km2. We find that centre flow line velocities of lake-terminating glaciers are more than double those of land-terminating glaciers (18.8 vs 8.24 m yr-1) and show substantially more heterogeneity around glacier termini. We attribute this large heterogeneity to the varying influence of lakes on glacier dynamics, resulting in differential rates of dynamic thinning, which effects about half of the clean-ice lake-terminating glacier population. Also, numerical ice-flow model experiments suggest that changes at the frontal boundary condition can play a key role in accelerating the glacier flow at the front. With continued warming new lake development is likely to happen and will further accelerate future ice mass losses, a scenario not currently considered in regional projections.&#160;

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Contrasting thinning patterns between lake- and land-terminating glaciers in the Bhutanese Himalaya

Cited by 47 publications

References 78 publications

Proglacial Lakes Control Glacier Geometry and Behavior During Recession

Proglacial Lakes Control Glacier Geometry and Behavior During Recession

Proglacial Lakes Elevate Glacier Surface Velocities in the Himalayan Region

Proglacial Lakes Elevate Glacier Surface Velocities in the Himalayan Region

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