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| Titel |
Representing moisture fluxes and phase changes in glacier debris cover using a reservoir approach |
| VerfasserIn |
E. Collier, L. I. Nicholson, B. W. Brock, F. Maussion, R. Essery, A. B. G. Bush |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1994-0416
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| Digitales Dokument |
URL |
| Erschienen |
In: The Cryosphere ; 8, no. 4 ; Nr. 8, no. 4 (2014-08-05), S.1429-1444 |
| Datensatznummer |
250116258
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| Publikation (Nr.) |
 copernicus.org/tc-8-1429-2014.pdf |
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| Zusammenfassung |
| Due to the complexity of treating moisture in supraglacial debris, surface
energy balance models to date have neglected moisture infiltration and phase
changes in the debris layer. The latent heat flux (QL) is also often excluded
due to the uncertainty in determining the surface vapour pressure. To
quantify the importance of moisture on the surface energy and climatic mass
balance (CMB) of debris-covered glaciers, we developed a simple reservoir
parameterization for the debris ice and water content, as well as an
estimation of the latent heat flux. The parameterization was incorporated
into a CMB model adapted for debris-covered glaciers. We present the results
of two point simulations, using both our new "moist" and the conventional
"dry" approaches, on the Miage Glacier, Italy, during summer 2008 and fall
2011. The former year coincides with available in situ glaciological and
meteorological measurements, including the first eddy-covariance measurements
of the turbulent fluxes over supraglacial debris, while the latter contains
two refreeze events that permit evaluation of the influence of phase changes.
The simulations demonstrate a clear influence of moisture on the glacier
energy and mass-balance dynamics. When water and ice are considered, heat
transmission to the underlying glacier ice is lower, as the effective thermal
diffusivity of the saturated debris layers is reduced by increases in both
the density and the specific heat capacity of the layers. In combination with
surface heat extraction by QL, subdebris ice melt is reduced by 3.1%
in 2008 and by 7.0% in 2011 when moisture effects are included.
However, the influence of the parameterization on the total accumulated mass
balance varies seasonally. In summer 2008, mass loss due to surface vapour
fluxes more than compensates for the reduction in ice melt, such that the
total ablation increases by 4.0%. Conversely, in fall 2011, the
modulation of basal debris temperature by debris ice results in a decrease in
total ablation of 2.1%. Although the parameterization is a simplified
representation of the moist physics of glacier debris, it is a novel attempt
at including moisture in a numerical model of debris-covered glaciers and one
that opens up additional avenues for future research. |
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