Calculating ice melt beneath a debris layer using meteorological data

Nicholson, Lindsey; Benn, Douglas I.

doi:10.3189/172756506781828584

Cited by 347 publications

(458 citation statements)

References 13 publications

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“…Furthermore, under the assumption of uniform debris conditions over larger areas (similar grain size distribution, similar lithology, similar water content), heat transfer is governed by thermal resistance. For daily observations, a linear vertical temperature gradient within the debris column can be expected (Nicholson and Benn, 2006) and it can be assumed that energy transferred through the debris cover depends on the temperature gradient dT/dz and its thermal resistance R only (Nakawo and Takahashi, 1982):…”

Section: Characteristics Of Sub-debris Ice Meltmentioning

confidence: 99%

“…Lambrecht et al: A comparison of glacier melt Nicholson and Benn, 2006) highlighting important differences between clear ice and sub-debris melt due to changes in individual terms of the energy balance. While net radiation is the main energy source for ice melt on debris-free glaciers, latent heat flux and conduction through the supra-glacial material determine the sub-debris melt rates .…”

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confidence: 99%

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A comparison of glacier melt on debris-covered glaciers in the northern and southern Caucasus

et al. 2011

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Abstract. The glacier coverage in the Caucasus Mountains underwent considerable changes during the last decades. In some regions, the observed reduction in glacier area is comparable to those in the European Alps and the extent of supra-glacial debris increased on many glaciers. Only a few glaciers in the Caucasus are monitored on a regular basis, while for most areas no continuous field measurements are available. In this study, regional differences of the conditions for glacier melt with a special focus on debris covered glacier tongues in the well-studied Adyl-su basin on the northern slope of the Caucasus Mountains (Russia) is compared with the Zopkhito basin which has similar characteristics but is located on the southern slope in Georgia. The paper focuses on the effect of supra-glacial debris cover on glacier summer melt. There are systematic differences in the distribution and increase of the debris cover on the glaciers of the two basins. In the Adyl-su basin an extensive debris cover on the glacier tongues is common, however, only those glacier tongues that are positioned at the lowest elevations in the Zopkhito basin show a considerable extent of supra-glacial debris. The observed increase in debris cover is considerably stronger in the north. Field experiments show that thermal resistance of the debris cover in both basins is somewhat higher than in other glaciated regions of the world, but there is also a significant difference between the two regions. A simple ablation model accounting for the effect of debris cover on ice melt shows that melt rates are considerably higher in the northern basin despite a wider debris distribution. This difference betweenCorrespondence to: A. Lambrecht (astrid.lambrecht@uibk.ac.at) the two regions can be attributed to different meteorological conditions which are characterised by more frequent cloud cover and precipitation in the south. Furthermore ablation is strongly influenced by the occurrence of supra-glacial debris cover in both basins, reducing the total amount of melt on the studied glaciers by about 25 %. This effect mitigates glacier retreat in the lower sectors of the ablation zones considerably. The sensitivity to moderate changes in the debris cover, however, is rather small which implies only gradual changes of the melt regime due to debris cover dynamics during the near future.

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Section: Characteristics Of Sub-debris Ice Meltmentioning

confidence: 99%

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confidence: 99%

A comparison of glacier melt on debris-covered glaciers in the northern and southern Caucasus

et al. 2011

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“…Energybased models are nowadays available for snow and ice melt (Lehning et al 2002;Nicholson and Benn 2006;Brock et al 2007), but they may require more information, including (present, and future for projections) subdaily solar radiation, wind velocity, and air moisture that were not available here, especially in the last 30 years. In this study, for hydrological model calibration we relied upon disaggregation of monthly data to reconstruct missing daily data, which may introduce noise at the daily scale.…”

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confidence: 99%

Future Hydrological Regimes in the Upper Indus Basin: A Case Study from a High-Altitude Glacierized Catchment

Soncini

Bocchiola

Confortola

et al. 2015

Journal of Hydrometeorology

104

124

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The mountain regions of the Hindu Kush, Karakoram, and Himalayas (HKH) are considered Earth's ''third pole,'' and water from there plays an essential role for downstream populations. The dynamics of glaciers in Karakoram are complex, and in recent decades the area has experienced unchanged ice cover, despite rapid decline elsewhere in the world (the Karakoram anomaly). Assessment of future water resources and hydrological variability under climate change in this area is greatly needed, but the hydrology of these high-altitude catchments is still poorly studied and little understood. This study focuses on a particular watershed, the Shigar River with the control section at Shigar (about 7000 km 2 ), nested within the upper Indus basin and fed by seasonal melt from two major glaciers (Baltoro and Biafo). Hydrological, meteorological, and glaciological data gathered during 3 years of field campaigns (2011-13) are used to set up a hydrological model, providing a depiction of instream flows, snowmelt, and ice cover thickness. The model is used to assess changes of the hydrological cycle until 2100, via climate projections provided by three state-of-the-art global climate models used in the recent IPCC Fifth Assessment Report under the representative concentration pathway (RCP) emission scenarios RCP2.6, RCP4.5, and RCP8.5. Under all RCPs, future flows are predicted to increase until midcentury and then to decrease, but remaining mostly higher than control run values. Snowmelt is projected to occur earlier, while the ice melt component is expected to increase, with ice thinning considerably and even disappearing below 4000 m MSL until 2100.

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“…First, there is the reduction of albedo induced by the particle cover (Warren and Wiscombe, 1980) and the resulting increase of absorbed global radiation and available melt energy. Second, there is the thermal resistance of the particle layer and the resulting decrease of heat conduction towards the glacier surface (Nicholson and Benn, 2006).…”

Section: Introductionmentioning

confidence: 99%

“…In general, the modification of glacier surface ablation by these types of supraglacial particle layers can be quantified by two different approaches. These are either statistics-based models that parameterize the impacts of particle covers on the basis of empirical data (Hagg and others, 2008;Lambrecht and others, 2011;Juen and others, 2014) or physics-based models that explicitly consider the heat conduction through the particle layer down to the glacier surface (Nicholson and Benn, 2006;Brock and others, 2010;Reid and Brock, 2010;Reid and others, 2012).…”

Section: Introductionmentioning

confidence: 99%

Impact of supraglacial deposits of tephra from Grímsvötn volcano, Iceland, on glacier ablation

Möller

Kukla

et al. 2016

J. Glaciol.

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ABSTRACT. Supraglacial deposits are known for their influence on glacier ablation. The magnitude of this influence depends on the thickness and the type of the deposited material. The effects of thin layers of atmospheric black carbon and of thick moraine debris have been intensively studied. Studies related to regional-scale deposits of volcanic tephra with thicknesses varying between millimetres and metres and thus over several orders of magnitude are scarce. We present results of a field experiment in which we investigated the influence of supraglacial deposits of tephra from Grímsvötn volcano on bare-ice ablation at Svínafelsjökull, Iceland. We observed that the effective thickness at which ablation is maximized ranges from 1.0 to 2.0 mm. At ∼10 mm a critical thickness is reached where sub-tephra ablation equals bare-ice ablation. We calibrated two empirical ablation models and a semi-physicsbased ablation model that all account for varying tephra-layer thicknesses. A comparison of the three models indicates that for tephra deposits in the lower-millimetre scale the temperature/radiationindex model performs best, but that a semi-physics-based approach could be expected to yield superior results for tephra deposits of the order of decimetres.

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Calculating ice melt beneath a debris layer using meteorological data

Cited by 347 publications

References 13 publications

A comparison of glacier melt on debris-covered glaciers in the northern and southern Caucasus

A comparison of glacier melt on debris-covered glaciers in the northern and southern Caucasus

Future Hydrological Regimes in the Upper Indus Basin: A Case Study from a High-Altitude Glacierized Catchment

Impact of supraglacial deposits of tephra from Grímsvötn volcano, Iceland, on glacier ablation

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