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| Titel |
Grease ice parameterisation in sea-ice ocean models |
| VerfasserIn |
Lars H. Smedsrud, Torge Martin, Jens Debernard |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250051804
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| Zusammenfassung |
| The first ice formation in Arctic and Antarctic waters is often grease ice, a mixture of sea
water and frazil ice crystals. Grease ice thus creates a gradual transition between water and
solid ice, a transition previously not resolved in sea-ice ocean models. A simple
way of modelling grease ice in large scale models is suggested here, capturing the
basic grease ice properties: a surface temperature at the freezing point, a ~25Â %
volume concentration of frazil ice, and a wind and current dependant grease ice
thickness.
The open water heat loss governs the grease ice production, and the transition to a solid
sea ice cover follows gradually over the next day when ~50Â % of the model grease ice area
forms pancake ice. The new grease ice parameterisation delays the transition from
open water to a solid ice cover, increasing ocean-to-air heat fluxes during freezing
conditions.
A basic version of the grease ice parametrisation is tested in a column model showing
that during mean winter Arctic conditions changes are moderate and heat fluxes
increase by ~1Â W/m2. Additional stronger heat fluxes are produced by the new
parameterisation under significant ice divergence, such as in a polynya, or for large initial
open water areas. As the effect of implementing grease ice becomes stronger with
larger open water areas, it will have a significant impact on the freeze-up conditions
in the simulations of the recent retreat of Arctic summer sea ice. The grease ice
parameterisation may thus provide a negative feedback for the recent ice loss and
contribute to a more robust model ice cover for both Arctic and Antarctic oceans. |
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