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| Titel |
New snow thermodynamics for the Louvain-la-Neuve Sea Ice Model (LIM) |
| VerfasserIn |
Olivier Lecomte, Thierry Fichefet |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250035054
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| Zusammenfassung |
| The Louvain-la-Neuve sea Ice Model (LIM) is a three-dimensional global model for sea ice
dynamics and thermodynamics that has been specifically designed for climate studies and
that is fully coupled with the oceanic general circulation model OPA on the modelling
platform NEMO. This study presents and assesses the skills of a new one-dimensional snow
model developed for the thermodynamic component of LIM, by comparison with the former
model thermodynamics and observations.
Snow is a key element in sea ice physics and in the interactions between sea ice and
atmosphere. Owing to its low thermal conductivity and hight albedo, the snow cover is a very
efficient insulator and it contributes directly and indirectly to the sea ice mass balance. Given
the high variability and heterogeneity of the snow cover above sea ice, it is necessary to
represent different types of snow, depending on their characteristics. A multilayer approach
has been chosen for the model, with time varying temperature, density and thermal
conductivity for each layer. Vertical heat diffusion, surface and internal melt, precipitations,
snow ice formation and a parameterisation for melt pond albedo are included in the
model.
The model has been validated at Ice Station POLarstern (ISPOL) in the western
Weddell Sea during summer and at Point Barrow (Alaska) during winter. The new
model simulates better temperature profiles, with an amount of good correlations
between modelled and observed profiles increasing from 12% to 42% for the 2-layer
and 6-layer configurations, respectively. Conductive fluxes and temperatures are
highly sensitive to albedo and ocean heat flux during summer, and to the thermal
conductivity parameterisation during winter. Ice ablation rate is quite insensitive to snow
thermal conductivity in summer because almost all the variability at the surface is
absorbed by snow, making the temperature gradient in the ice relatively small and
steady. Nevertheless, during winter, when the air temperature falls far below the
freezing point, thermal conductivity plays a larger role as temperature gradients
steepen and drive the amount of "cold" transmitted to the ice. Overall, accretion rates
and ice maximum thicknesses are in better agreement with observations. Further
tests must be undertaken to assess the model skills under coupled conditions and
determine the minimum number of layers to keep for global-scale simulation purposes. |
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