A distributed energy-balance melt model of an alpine debris-covered glacier

Fyffe, Catriona; Reid, Tim; Brock, Benjamin; Kirkbride, Martin P.; Diolaiuti, Guglielmina; Smiraglia, Claudio; Diotri, Fabrizio

doi:10.3189/2014jog13j148

Cited by 61 publications

(93 citation statements)

References 48 publications

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“…8 in the terminus zone. However, other areas of the ablation zone are affected by a thin and patchy layer of debris or aerosol, which is likely to increase ablation through local albedo reduction (Fyffe et al, 2014). Although quantification of the effects of debris on melt is beyond the scope of this study, it would be expected that impacts of thick morainic debris and thin patchy debris elsewhere will tend to compensate in overall melt estimations for the glacier.…”

Section: Modelling Approach and Uncertaintiesmentioning

confidence: 99%

Assessing glacier melt contribution to streamflow at Universidad Glacier, central Andes of Chile

Bravo

Loriaux

Rivera

et al. 2017

Hydrol. Earth Syst. Sci.

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Abstract. Glacier melt is an important source of water for high Andean rivers in central Chile, especially in dry years, when it can be an important contributor to flows during late summer and autumn. However, few studies have quantified glacier melt contribution to streamflow in this region. To address this shortcoming, we present an analysis of meteorological conditions and ablation for Universidad Glacier, one of the largest valley glaciers in the central Andes of Chile at the head of the Tinguiririca River, for the 2009-2010 ablation season. We used meteorological measurements from two automatic weather stations installed on the glacier to drive a distributed temperature-index and runoff routing model. The temperature-index model was calibrated at the lower weather station site and showed good agreement with melt estimates from an ablation stake and sonic ranger, and with a physically based energy balance model. Total modelled glacier melt is compared with river flow measurements at three sites located between 0.5 and 50 km downstream. Universidad Glacier shows extremely high melt rates over the ablation season which may exceed 10 m water equivalent in the lower ablation area, representing between 10 and 13 % of the mean monthly streamflow at the outlet of the Tinguiririca River Basin between December 2009 and March 2010. This contribution rises to a monthly maximum of almost 20 % in March 2010, demonstrating the importance of glacier runoff to streamflow, particularly in dry years such as 2009-2010. The temperature-index approach benefits from the availability of on-glacier meteorological data, enabling the calculation of the local hourly variable lapse rate, and is suited to high melt regimes, but would not be easily applicable to glaciers further north in Chile where sublimation is more significant.

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Section: Modelling Approach and Uncertaintiesmentioning

confidence: 99%

Assessing glacier melt contribution to streamflow at Universidad Glacier, central Andes of Chile

Bravo

Loriaux

Rivera

et al. 2017

Hydrol. Earth Syst. Sci.

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“…Collier et al (2014) suggested that if the atmospheric surface layer is well mixed, then the water vapor partial pressure between the surface and the air may be assumed to be constant, thereby resulting in a latent heat flux based on the vapor pressure gradient. Fyffe et al (2014) also commented that the lower portion of the debris near the ice interface was observed to be saturated indicating that there may be evaporation and condensation occurring within the debris, albeit small, even when the surface relative humidity is less than 100 %. The lack of knowledge of the moisture in the debris and at its surface makes it difficult to accurately model the latent heat flux term.…”

Section: Introductionmentioning

confidence: 99%

“…In particular, knowledge related to the latent heat flux on debris-covered glaciers is very limited. This has led previous studies to assume the surface is dry (Foster et al, 2012;Lejeune et al, 2013;Rounce and McKinney, 2014), assume it is dry unless the surface relative humidity was 100 % (Reid and Brock, 2010;Reid et al, 2012;Fyffe et al, 2014), assume a relationship between debris thickness and wetness (Fujita and Sakai, 2014), or use a reservoir approach to model the moisture in the debris (Collier et al, 2014). Collier et al (2014) suggested that if the atmospheric surface layer is well mixed, then the water vapor partial pressure between the surface and the air may be assumed to be constant, thereby resulting in a latent heat flux based on the vapor pressure gradient.…”

Section: Introductionmentioning

confidence: 99%

Debris-covered glacier energy balance model for Imja–Lhotse Shar Glacier in the Everest region of Nepal

2015

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Abstract. Debris thickness plays an important role in regulating ablation rates on debris-covered glaciers as well as controlling the likely size and location of supraglacial lakes. Despite its importance, lack of knowledge about debris properties and associated energy fluxes prevents the robust inclusion of the effects of a debris layer into most glacier surface energy balance models. This study combines fieldwork with a debris-covered glacier energy balance model to estimate debris temperatures and ablation rates on Imja-Lhotse Shar Glacier located in the Everest region of Nepal. The debris properties that significantly influence the energy balance model are the thermal conductivity, albedo, and surface roughness. Fieldwork was conducted to measure thermal conductivity and a method was developed using Structure from Motion to estimate surface roughness. Debris temperatures measured during the 2014 melt season were used to calibrate and validate a debris-covered glacier energy balance model by optimizing the albedo, thermal conductivity, and surface roughness at 10 debris-covered sites. Furthermore, three methods for estimating the latent heat flux were investigated. Model calibration and validation found the three methods had similar performance; however, comparison of modeled and measured ablation rates revealed that assuming the latent heat flux is zero may overestimate ablation. Results also suggest that where debris moisture is unknown, measurements of the relative humidity or precipitation may be used to estimate wet debris periods, i.e., when the latent heat flux is non-zero. The effect of temporal resolution on the model was also assessed and results showed that both 6 h data and daily average data slightly underestimate debris temperatures and ablation rates; thus these should only be used to estimate rough ablation rates when no other data are available.

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“…As such, accurate quantification of T a in distributed melt models is required for studies of glacier mass balance (e.g. Reijmer and Hock, 2008;Engelhardt andothers, 2013, Gabbi andothers, 2014), water resource availability (e.g. Nolin and others, 2010) and glacier contributions to sea-level rise (e.g.…”

Section: Introductionmentioning

confidence: 99%

Centreline and cross-glacier air temperature variability on an Alpine glacier: assessing temperature distribution methods and their influence on melt model calculations

et al. 2017

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ABSTRACT. The spatio-temporal distribution of air temperature over mountain glaciers can demonstrate complex patterns, yet it is often represented simplistically using linear vertical temperature gradients (VTGs) extrapolated from off-glacier locations. We analyse a network of centreline and lateral air temperature observations at Tsanteleina Glacier, Italy, during summer 2015. On average, VTGs are steep), but they are shallow under warm ambient conditions when the correlation between air temperature and elevation becomes weaker. Published along-flowline temperature distribution methods explain centreline observations well, including warming on the lower glacier tongue, but cannot estimate lateral temperature variability. Application of temperature distribution methods improves simulation of melt rates (RMSE) in an energy-balance model by up to 36% compared to the environmental lapse rate extrapolated from an off-glacier station. However, results suggest that model parameters are not easily transferable to glaciers with a small fetch without recalibration. Such methods have potential to improve estimates of temperature across a glacier, but their parameter transferability should be further linked to the glacier and atmospheric characteristics. Furthermore, 'cold spots', which can be >2°C cooler than expected for their elevation, whose occurrence is not predicted by the temperature distribution models, are identified at one-quarter of the measurement sites.

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A distributed energy-balance melt model of an alpine debris-covered glacier

Cited by 61 publications

References 48 publications

Assessing glacier melt contribution to streamflow at Universidad Glacier, central Andes of Chile

Assessing glacier melt contribution to streamflow at Universidad Glacier, central Andes of Chile

Debris-covered glacier energy balance model for Imja–Lhotse Shar Glacier in the Everest region of Nepal

Centreline and cross-glacier air temperature variability on an Alpine glacier: assessing temperature distribution methods and their influence on melt model calculations

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