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| Titel |
Laboratory study of frazil ice accumulation under wave conditions |
| VerfasserIn |
S. Rosa, S. Maus |
| 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 ; 6, no. 1 ; Nr. 6, no. 1 (2012-02-09), S.173-191 |
| Datensatznummer |
250003383
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| Publikation (Nr.) |
 copernicus.org/tc-6-173-2012.pdf |
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| Zusammenfassung |
| Ice growth in turbulent seawater is often accompanied by the accumulation of
frazil ice crystals at its surface, forming a grease ice layer. The
thickness and volume fraction of this ice layer play an important role in
shaping the gradual transition from a loose to a solid ice cover, however,
observations are very sparse. Here we analyse an extensive set of
observations of frazil ice, grown in two parallel tanks with controlled wave
conditions and thermal forcing, focusing on the first one to two days of
grease ice accumulation. The following unresolved issues are addressed: (i)
at which volume fraction the frazil crystals' rising process starts and how
densely they accumulate at the surface, (ii) how the grease ice solid
fraction and salinity evolve with time until solid ice starts to form and
(iii) how do these conditions affect, and are affected by, waves and heat
loss from the ice. We obtained estimates of the minimum initial grease ice
solid fraction (0.03–0.05) and the maximum solid fraction to which it
accumulates before freezing into pancakes (0.23–0.31). The equivalent
thickness of solid ice that needs to be accumulated until grease ice packs
close to maximum (95% of the compaction accomplished), was estimated as
0.4 to 1.2 cm. Comparison of grease ice thickness and wave observations
indicates that a grease ice layer first begins to affect the wave field
significantly when its thickness exceeds the initial wave amplitude. These
results are relevant for modelling frazil ice accumulation and freeze-up of
leads, polynyas and along the seasonal ice zone. |
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