On the importance of the albedo parameterization for the mass balance of the Greenland ice sheet in EC-Earth
The albedo of the surface of ice sheets changes as a function of time due to the effects of deposition of new snow, ageing of dry snow, bare ice exposure, melting and run-off. Currently, the calculation of the albedo of ice sheets is highly parameterized within the earth system model EC-Earth by...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-08-01
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| Series: | The Cryosphere |
| Online Access: | https://www.the-cryosphere.net/11/1949/2017/tc-11-1949-2017.pdf |
| Summary: | The albedo of the surface of ice sheets changes as a function of time due to
the effects of deposition of new snow, ageing of dry snow, bare ice exposure,
melting and run-off. Currently, the calculation of the albedo of ice sheets
is highly parameterized within the earth system model EC-Earth by taking a
constant value for areas with thick perennial snow cover. This is an
important reason why the surface mass balance (SMB) of the Greenland ice
sheet (GrIS) is poorly resolved in the model. The purpose of this study is to
improve the SMB forcing of the GrIS by evaluating different parameter
settings within a snow albedo scheme. By allowing ice-sheet albedo to vary as
a function of wet and dry conditions, the spatial distribution of albedo and
melt rate improves. Nevertheless, the spatial distribution of SMB in EC-Earth
is not significantly improved. As a reason for this, we identify omissions in
the current snow albedo scheme, such as separate treatment of snow and ice
and the effect of refreezing. The resulting SMB is downscaled from the
lower-resolution global climate model topography to the higher-resolution
ice-sheet topography of the GrIS, such that the influence of these different
SMB climatologies on the long-term evolution of the GrIS is tested by
ice-sheet model simulations. From these ice-sheet simulations we conclude
that an albedo scheme with a short response time of decaying albedo during
wet conditions performs best with respect to long-term simulated ice-sheet
volume. This results in an optimized albedo parameterization that can be used
in future EC-Earth simulations with an interactive ice-sheet component.</p> |
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| ISSN: | 1994-0416 1994-0424 |