Interannual climate variability helps define the mean state of glaciers

Malone, A.; Doughty, Alice M.; MacAyeal, Douglas R.

doi:10.1017/jog.2019.28

Cited by 8 publications

(5 citation statements)

References 56 publications

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“…The equilibrium line altitude (ELA, ~4950m in the current climate) denotes the altitude above which there is net accumulation and below which there is net ablation. A simple and robust method of quantifying the impact of climate change on glacier mass balance is via geometric shifts of the mass-balance profile in response to temperature and precipitation changes [31][32][33][34] . The climatological precipitation is important for the shape of the mass-balance profile but, on century timescales, precipitation trends are small and temperature changes dominate mass-balance changes 33,35 (see also Methods and Supplementary Materials).…”

Section: Attribution Of Palcaraju Glacier Retreat To Climate Changementioning

confidence: 99%

“…Consistent gradients can also be seen, for example, over 10 years at Uruashraju in Peru 36 , with similar results found for Zongo glacier in Bolivia 58 and elsewhere in the tropics 59 . The near-constant year-on-year shape of the mass-balance profiles means that vertical and horizontal shifts of the mass-balance profile are a useful and efficient approximation to represent climate forcing 31,32,34 .…”

Section: Vertical Profile Of Mass Balancementioning

confidence: 99%

“…Following refs. 34,36,60 , the impact of temperature anomaly ( ′) is implemented by vertically shifting the mass balance by an amount ′ = ′ /Γ , where Γ = 5.5 x 10 -3 K km -1 is the observed lapse rate 30,57 . We quantify the impact of a precipitation anomaly by adding a uniform anomaly to the mass-balance profile (a horizontal shift in Fig 2b).…”

Section: Climate Sensitivity Of Mass Balancementioning

confidence: 99%

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Increased outburst flood hazard from Lake Palcacocha due to human-induced glacier retreat

Stuart-Smith

Roe

et al. 2021

Nat. Geosci.

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A potential glacial lake outburst flood from Lake Palcacocha (Cordillera Blanca, Peru) threatens Huaraz, a city of 120,000 people. In 1941, an outburst flood destroyed one-third of the city and caused at least 1800 fatalities. Since preindustrial times, Lake Palcacocha has expanded due to the retreat of Palcaraju glacier. Here we present the first detailed study evaluating the anthropogenic contribution to the glacier's retreat and glacial lake outburst flood hazard. We find that the magnitude of human-induced warming equals between 85 and 105% (5-95% confidence interval) of the observed 1 °C warming since 1880 in this region. Using observations and numerical models of the mass balance and glacier response, we conclude that it is virtually certain (>99% probability) that the retreat of Palcaraju glacier to the present day cannot be explained by natural variability alone, and that the retreat by 1941 represented an early impact of anthropogenic greenhouse gas emissions. Our central estimate is that

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Section: Attribution Of Palcaraju Glacier Retreat To Climate Changementioning

confidence: 99%

Section: Vertical Profile Of Mass Balancementioning

confidence: 99%

Section: Climate Sensitivity Of Mass Balancementioning

confidence: 99%

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Increased outburst flood hazard from Lake Palcacocha due to human-induced glacier retreat

Stuart-Smith

Roe

et al. 2021

Nat. Geosci.

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“…No change in slope is detected for Kokanee, Illecillewaet or Zillmer glaciers when fit with a piecewise function. The ELA is the breakpoint for our piecewise functions (Furbish and Andrews, 1984;Malone et al, 2019). Uncertainties on balance gradients are taken as the standard error (SE) of the slope (Rabatel et al, 2005) for linear and piecewise functions.…”

Section: Surface Mass Balancementioning

confidence: 99%

Surface Mass-Balance Gradients From Elevation and Ice Flux Data in the Columbia Basin, Canada

Pelto

Menounos

2021

Front. Earth Sci.

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The mass-balance—elevation relation for a given glacier is required for many numerical models of ice flow. Direct measurements of this relation using remotely-sensed methods are complicated by ice dynamics, so observations are currently limited to glaciers where surface mass-balance measurements are routinely made. We test the viability of using the continuity equation to estimate annual surface mass balance between flux-gates in the absence of in situ measurements, on five glaciers in the Columbia Mountains of British Columbia, Canada. Repeat airborne laser scanning surveys of glacier surface elevation, ice penetrating radar surveys and publicly available maps of ice thickness are used to estimate changes in surface elevation and ice flux. We evaluate this approach by comparing modeled to observed mass balance. Modeled mass-balance gradients well-approximate those obtained from direct measurement of surface mass balance, with a mean difference of +6.6 ± 4%. Regressing modeled mass balance, equilibrium line altitudes are on average 15 m higher than satellite-observations of the transient snow line. Estimates of mass balance over flux bins compare less favorably than the gradients. Average mean error (+0.03 ± 0.07 m w.e.) between observed and modeled mass balance over flux bins is relatively small, yet mean absolute error (0.55 ± 0.18 m w.e.) and average modeled mass-balance uncertainty (0.57 m w.e.) are large. Mass conservation, assessed with glaciological data, is respected (when estimates are within 1σ uncertainties) for 84% of flux bins representing 86% of total glacier area. Uncertainty on ice velocity, especially for areas where surface velocity is low (<10 m a−1) contributes the greatest error in estimating ice flux. We find that using modeled ice thicknesses yields comparable modeled mass-balance gradients relative to using observations of ice thickness, but we caution against over-interpreting individual flux-bin mass balances due to large mass-balance residuals. Given the performance of modeled ice thickness and the increasing availability of ice velocity and surface topography data, we suggest that similar efforts to produce mass-balance gradients using modern high-resolution datasets are feasible on larger scales.

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“…We assess the mass-balance profile by approximating the profile as a single linear function (db/dz) and as a piecewise function comprised of two linear functions above (db + /dz) and below the ELA (db − /dz). The ELA is thus the breakpoint for our piecewise functions (Furbish & Andrews, 1984;Malone, Doughty, & Macayeal, 2019). Uncertainties on balance gradients are taken as the standard error (SE) of the slope (Rabatel, Dedieu, & Vincent, 2005) for linear gradients and the piecewise functions.…”

Section: Surface Mass Balancementioning

confidence: 99%

An approach to remotely monitor glacier mass balance at seasonal to annual time scales, Columbia and Rocky Mountains, Canada.

Pelto¹

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My dissertation investigates glacier mass change in the Columbia and Rocky Mountains of British Columbia. In chapter one I discuss the importance of the cryosphere and glaciers, introduce the climate and glaciers of the study region, and outline the objectives and structure of this dissertation. Previous work established the feasibility of geodetic methods to accurately produce winter glacier mass balance and annual glacier mass balance. These studies demonstrate that geodetic surveys can be used to estimate mass balance during the accumulation season or for one glacier over a number of years. In chapter two, I refine these published methods to measure seasonal and annual mass balance for six glaciers within two mountain ranges from 2014–2018. I use synchronous field-based glaciological measurements, airbornelaser scanningsurveys (ALS) and satelliteimagery to quantify seasonal glacier mass change from 2014–2018. Chapter three reports on radar surveys I completed of the study glaciers, adding important observations to the global database of ice thickness. I use these observations and an existing flowline model, driven with observations of surface mass balance and glacier elevation to bias-correct ice thickness estimates for each glacier. Finally, I use the model to estimate ice thickness for all glaciers in the Columbia Basin and estimate total ice volume. Chapter four builds upon previous work which used surface topography, glacier mass balance, ice thickness, and ice velocity data to estimate ice flux at discrete glacier cross-sections. Previous efforts to infer the spatial distribution of mass balance have focused on glacier tongues. I expand upon this method, calculating surface mass balance between flux gates over the entire elevation range of three glaciers, over three years. I derive the altitude-mass balance relation and demonstrate that the relation can be accurately described with high-resolution elevation and ice flux data, and suggest that this method can be expanded for large-scale estimates. Chapter five summarizes the study’s major findings, highlights its limitations and discussed its broader implications. Finally, I make recommendations that will address knowledge gaps, and improve our understanding of changing glacier conditions and ability to model glacier dynamics.

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Interannual climate variability helps define the mean state of glaciers

Cited by 8 publications

References 56 publications

Increased outburst flood hazard from Lake Palcacocha due to human-induced glacier retreat

Increased outburst flood hazard from Lake Palcacocha due to human-induced glacier retreat

Surface Mass-Balance Gradients From Elevation and Ice Flux Data in the Columbia Basin, Canada

An approach to remotely monitor glacier mass balance at seasonal to annual time scales, Columbia and Rocky Mountains, Canada.

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