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Atmospheric mesoscale effects on the surface mass and energy balance of polar ice caps


To improve the understanding and the representation in models of
the small scale physical processes playing a role in the surface
energy fluxes and mass balance over the polar ice caps (Greenland
and Antarctica).

The mass balance of the polar ice caps depends strongly on the
interaction with the atmopshere. Due to the large extent of the
ice-sheets sloped surface, katabatic winds develop and influence
strongly the snow and ice energy balance. The role of these
winds is very important for the ice- sheets mass balance, mainly
along the ice margin and over the ablation zone, where the
temperature may increase above 0º C in summer. These
phenomena are of typical mesoscale size and are badly treated in the
current General Circulation Models (GCM's).

In the past, this fact has been taken into account in a rather
simple way mainly because of a lack of experimental data from the
polar regions. But recently, several experiments have been
conducted in the polar regions and measurements of atmospheric
surface fluxes are available. It is now possible to test and
validate mesoscale meteorological models on these data, and then
use the model results to infer the behaviour of the
ice-atmosphere interaction in various conditions.

The project will use the data sets obtained from the Greenland
Ice Margin Experiments (GIMEX-90 and 91) for the Artic zone, and
those from Terra Nova Bay and IAGO for the Antarctic. The
sensible and latent fluxes are extracted from the observations
using adequate profile methods and the data are carefully
examined to study the albedo behaviour of the ice sheet, this
being an important factor of the surface energy balance

Two meteorological mesoscale models are used to perform the
simulations. The model physics is improved to come reasonnably
close to the observations. The physics taken into account in the
models must include such processes as: temperature stratification
in the katabatic flow, transport of snow, radiative cooling over
the icesheet and iceshelf, effect of the snow-free tundra, albedo
variation in function of height and summer melting in the
ablation region. The simulations schedule include also a
sensitivity study to these effects, and particularly the effect
of typical high latitude clouds on the surface fluxes and thus on
the melting rates.

Finally, a modelling experiment will be conducted to infer the
modification to the current fluxes and ablation rates expected
while forcing the models with external conditions foreseen for
the mid next century, due to enhanced greenhouse effect as
predicted by the current GCM's.

Funding Scheme

CSC - Cost-sharing contracts


2,Chemin Du Cyclotron 2
1348 Louvain-la-neuve

Participants (2)

Avenue Edouard Belin 14
31400 Toulouse
5,Princetonplein 5
3584 CC Utrecht