Debris-covered glacier energy balance model for Imja–Lhotse Shar Glacier in the Everest region of Nepal
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...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2015-12-01
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| Series: | The Cryosphere |
| Online Access: | http://www.the-cryosphere.net/9/2295/2015/tc-9-2295-2015.pdf |
| _version_ | 1819280483526115328 |
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| author | D. R. Rounce D. J. Quincey D. C. McKinney |
| author_facet | D. R. Rounce D. J. Quincey D. C. McKinney |
| author_sort | D. R. Rounce |
| collection | DOAJ |
| description | 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. |
| first_indexed | 2024-12-24T00:44:31Z |
| format | Article |
| id | doaj.art-985ebbb795894a01be3eb707dbbe9ac7 |
| institution | Directory Open Access Journal |
| issn | 1994-0416 1994-0424 |
| language | English |
| last_indexed | 2024-12-24T00:44:31Z |
| publishDate | 2015-12-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | The Cryosphere |
| spelling | doaj.art-985ebbb795894a01be3eb707dbbe9ac72022-12-21T17:23:51ZengCopernicus PublicationsThe Cryosphere1994-04161994-04242015-12-01962295231010.5194/tc-9-2295-2015Debris-covered glacier energy balance model for Imja–Lhotse Shar Glacier in the Everest region of NepalD. R. Rounce0D. J. Quincey1D. C. McKinney2Center for Research in Water Resources, University of Texas at Austin, Austin, Texas, USASchool of Geography, University of Leeds, Leeds, LS2 9JT, UKCenter for Research in Water Resources, University of Texas at Austin, Austin, Texas, USADebris 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.http://www.the-cryosphere.net/9/2295/2015/tc-9-2295-2015.pdf |
| spellingShingle | D. R. Rounce D. J. Quincey D. C. McKinney Debris-covered glacier energy balance model for Imja–Lhotse Shar Glacier in the Everest region of Nepal The Cryosphere |
| title | Debris-covered glacier energy balance model for Imja–Lhotse Shar Glacier in the Everest region of Nepal |
| title_full | Debris-covered glacier energy balance model for Imja–Lhotse Shar Glacier in the Everest region of Nepal |
| title_fullStr | Debris-covered glacier energy balance model for Imja–Lhotse Shar Glacier in the Everest region of Nepal |
| title_full_unstemmed | Debris-covered glacier energy balance model for Imja–Lhotse Shar Glacier in the Everest region of Nepal |
| title_short | Debris-covered glacier energy balance model for Imja–Lhotse Shar Glacier in the Everest region of Nepal |
| title_sort | debris covered glacier energy balance model for imja lhotse shar glacier in the everest region of nepal |
| url | http://www.the-cryosphere.net/9/2295/2015/tc-9-2295-2015.pdf |
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