Frazil-ice growth rate and dynamics in mixed layers and sub-ice-shelf plumes
The growth of frazil or granular ice is an important mode of ice formation in the cryosphere. Recent advances have improved our understanding of the microphysical processes that control the rate of ice-crystal growth when water is cooled beneath its freezing temperature. These advances suggest th...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-01-01
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| Series: | The Cryosphere |
| Online Access: | https://www.the-cryosphere.net/12/25/2018/tc-12-25-2018.pdf |
| Summary: | The growth of frazil or granular ice is an important mode of ice formation in
the cryosphere. Recent advances have improved our understanding of the
microphysical processes that control the rate of ice-crystal growth when
water is cooled beneath its freezing temperature. These advances suggest that
crystals grow much faster than previously thought. In this paper, we consider
models of a population of ice crystals with different sizes to provide
insight into the treatment of frazil ice in large-scale models. We consider
the role of crystal growth alongside the other physical processes that
determine the dynamics of frazil ice. We apply our model to a simple mixed
layer (such as at the surface of the ocean) and to a buoyant plume under a
floating ice shelf. We provide numerical calculations and scaling arguments
to predict the occurrence of frazil-ice explosions, which we show are
controlled by crystal growth, nucleation, and gravitational removal. Faster
crystal growth, higher secondary nucleation, and slower gravitational removal
make frazil-ice explosions more likely. We identify steady-state crystal size
distributions, which are largely insensitive to crystal growth rate but are
affected by the relative importance of secondary nucleation to gravitational
removal. Finally, we show that the fate of plumes underneath ice shelves is
dramatically affected by frazil-ice dynamics. Differences in the
parameterization of crystal growth and nucleation give rise to radically
different predictions of basal accretion and plume dynamics, and can even
impact whether a plume reaches the end of the ice shelf or intrudes at depth. |
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| ISSN: | 1994-0416 1994-0424 |