Reanalysing the 2007–19 glaciological mass-balance series of Mera Glacier, Nepal, Central Himalaya, using geodetic mass balance

Wagnon, Patrick; Brun, Fanny; Khadka, Arbindra; Berthier, Étienne; Shrestha, Dibas; Vincent, Christian; Arnaud, Yves; Six, Delphine; Dehecq, Amaury; Ménégoz, Martin; Jomelli, Vincent

doi:10.1017/jog.2020.88

Cited by 40 publications

(53 citation statements)

References 41 publications

(58 reference statements)

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“…The accuracy of the elevation product is first assessed by comparing the photogrammetrically created DSMs with GVPs, randomly divided over the study area. MAE between measured and modelled elevation is on the order of a few centimetres (Table 2), which is similar to values found in other studies (Whitehead et al, 2013;Immerzeel et al, 2014;Wigmore and Mark, 2017;Zhang et al, 2019). As such, the accuracy of the created DSMs is high.…”

Section: Surface Elevation Changes and Filteringsupporting

confidence: 87%

Estimating surface mass balance patterns from unoccupied aerial vehicle measurements in the ablation area of the Morteratsch–Pers glacier complex (Switzerland)

et al. 2021

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Abstract. The surface mass balance (SMB) of a glacier provides the link between the glacier and the local climate. For this reason, it is intensively studied and monitored. However, major efforts are required to determine the point SMB at a sufficient number of locations to capture the heterogeneity of the SMB pattern. Furthermore, because of the time-consuming and costly nature of these measurements, detailed SMB measurements are carried out on only a limited number of glaciers. In this study, we investigate how to accurately determine the SMB in the ablation zone of Vadret da Morteratsch and Vadret Pers (Engadin, Switzerland) using the continuity equation method, based on the expression of conservation of mass for glacier flow with constant density. An elaborate dataset (spanning the 2017–2020 period) of high-resolution data derived from unoccupied aerial vehicle (UAV) measurements (surface elevation changes and surface velocities) is combined with reconstructed ice thickness fields (based on radar measurements). To determine the performance of the method, we compare modelled SMB with measured SMB values at the position of stakes. Our results indicate that with annual UAV surveys, it is possible to obtain SMB estimates with a mean absolute error smaller than 0.5 m of ice equivalent per year. Yet, our study demonstrates that to obtain these accuracies, it is necessary to consider the ice flow over spatial scales of several times the local ice thickness, accomplished in this study by applying an exponential decay filter. Furthermore, our study highlights the crucial importance of the ice thickness, which must be sufficiently well known in order to accurately apply the method. The latter currently seems to complicate the application of the continuity equation method to derive detailed SMB patterns on regional to global scales.

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Section: Surface Elevation Changes and Filteringsupporting

confidence: 87%

Estimating surface mass balance patterns from unoccupied aerial vehicle measurements in the ablation area of the Morteratsch–Pers glacier complex (Switzerland)

et al. 2021

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“…a −1 [55]. However, the uncertainty estimated in our study was smaller than the similar studies that used coarse DEMs (e.g., [56][57][58]), confirming the high precision of the TLS surveys. Note that this study only focused on glacier mass balance in the ablation area, and uncertainties in estimated accumulation had not been considered, which probably improved the accuracy of geodetic mass balance [59].…”

Section: Accuracy Of Dem Differencing and Geodetic Mass Balancesupporting

confidence: 77%

Spatio-Temporal Changes of Mass Balance in the Ablation Area of the Muz Taw Glacier, Sawir Mountains, from Multi-Temporal Terrestrial Geodetic Surveys

Wang

et al. 2021

Remote Sensing

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The glaciers in the Sawir Mountains are an important freshwater resource, and glaciers have been experiencing a continuing retreat over the past few decades. However, studies on detailed glacier mass changes are currently sparse. Here, we present the high-precision evolution of annual surface elevation and geodetic mass changes in the ablation area of the Muz Taw Glacier (Sawir Mountains, China) over the latest three consecutive mass-balance years (2017–2020) based on multi-temporal terrestrial geodetic surveys. Our results revealed clearly surface lowering and negative geodetic mass changes, and the spatial changing patterns were generally similar for the three periods with the most negative surface lowering (approximately −5.0 to −4.0 m a−1) around the glacier terminus. The gradient of altitudinal elevation changes was commonly steep at the low elevations and gentle in the upper-elevation parts, and reduced surface lowering was observed at the glacier terminus. Resulting emergence velocities ranged from 0.11 to 0.86 m a−1 with pronounced spatial variability, which was mainly controlled by surface slope, ice thickness, and the movement of tributary glaciers. Meanwhile, emergence velocities slightly compensated the surface ablation at the ablation area with a proportion of 14.9%, and dynamic thickening had small contributions to glacier surface evolution. Limited annual precipitation and glacier accumulation may result in these weak contributions. Higher-resolution surveys at the seasonal and monthly scales are required to get insight into the mass balance processes and their mechanism.

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“…Extrapolating point measurements to the entire glacier area is, however, subject to considerable uncertainties (Fountain and Vecchia, 1999; Cox and March, 2004; Holmlund and others, 2005; Thibert and others, 2008). Re-analysis at regular intervals combining direct point observations with independent geodetic mass changes is therefore recommended (Haeberli and others, 2007; Zemp and others, 2013), and is performed based on a wide range of approaches (Huss and others, 2009a; Van Beusekom and others, 2010; Barandun and others, 2015; Andreassen and others, 2016; Klug and others, 2018; O'Neel and others, 2019; Wagnon and others, 2021). In the case of Claridenfirn, computation of glacier-wide mass balance is further complicated due to ice losses by break-off at a frontal ice cliff.…”

Section: Introductionmentioning

confidence: 99%

More than a century of direct glacier mass-balance observations on Claridenfirn, Switzerland

et al. 2021

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Glacier mass-balance observations at seasonal resolution have been performed since 1914 at two sites on Claridenfirn, Switzerland. The measurements are the longest uninterrupted records of glacier mass balance worldwide. Here, we provide a complete re-analysis of the 106-year series (1914–2020), focusing on both point and glacier-wide mass balance. The approaches to evaluate and homogenize the direct observations are described in detail. Based on conservative assumptions, average uncertainties of $\pm$ 0.25 m w.e. are estimated for glacier-wide mass balances at the annual scale. It is demonstrated that long-term variations in mass balance are clearly driven by melting, whereas decadal changes in accumulation are uncorrelated with mass balance and can only be relevant in short periods. Mass change of Claridenfirn is impacted by dry calving at a frontal ice cliff. Considerations of ice volume flux at a cross-profile reveal long-term variations in frontal ice loss accounting for $\sim$ 9% of total annual ablation on average. The effect of changes in frontal ablation mostly explains $\lt$ 10% of the mass-balance difference relative to the period 1960–1990, but accounts for $\sim$ 20% in 2010–2020. Glacier mass changes are discussed in the context of observations throughout the European Alps indicating that Claridenfirn is regionally representative.

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Reanalysing the 2007–19 glaciological mass-balance series of Mera Glacier, Nepal, Central Himalaya, using geodetic mass balance

Cited by 40 publications

References 41 publications

Estimating surface mass balance patterns from unoccupied aerial vehicle measurements in the ablation area of the Morteratsch–Pers glacier complex (Switzerland)

Estimating surface mass balance patterns from unoccupied aerial vehicle measurements in the ablation area of the Morteratsch–Pers glacier complex (Switzerland)

Spatio-Temporal Changes of Mass Balance in the Ablation Area of the Muz Taw Glacier, Sawir Mountains, from Multi-Temporal Terrestrial Geodetic Surveys

More than a century of direct glacier mass-balance observations on Claridenfirn, Switzerland

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