Salt fluxes from sea ice: simple models of reactively dissolved channels
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| Description: |
Rees Jones, D (University of Oxford)
Thursday 9th June 2016 - 14:45 to 15:30 |
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| Created: | 2016-06-16 09:57 |
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| Collection: | Melt in the Mantle |
| Publisher: | Isaac Newton Institute |
| Copyright: | Rees Jones, D |
| Language: | eng (English) |
| Distribution: |
World
(downloadable)
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| Explicit content: | No |
| Aspect Ratio: | 16:9 |
| Screencast: | No |
| Bumper: | UCS Default |
| Trailer: | UCS Default |
| Abstract: | Sea ice is a geophysically important material that bears some similarity to the partially molten mantle. Newly formed sea ice contains a significant amount of salt as liquid brine in the interstices of a permeable ice matrix through which the brine can flow. Compositional convection drives fluid motion within porous sea ice. The convective circulation leads to the development of so-called 'brine channels,' liquid channels formed by a dissolution reaction. I discuss the physical mechanisms that create and sustain these channels. Some aspects of these mechanisms may apply to reactive channelization of magmatic flow through the mantle beneath mid-ocean ridges, for example.
Salt fluxes through brine channels are an important buoyancy forcing for the polar oceans, with implications for ocean mixing and deep-water formation. I develop a simple, semi-analytical Chimney-Active-Passive (CAP) model of convection in sea ice. I investigate the physical controls on the convective velocities, brine channel size, and salt fluxes. I test my predictions by considering previous laboratory observations of the propagation of dye fronts within the ice and salt fluxes from it. Finally, I take a one-dimensional, thermodynamic sea-ice model of the kind currently used in coupled climate models and parameterize porous convection within a one-dimensional model. The parameterization allows dynamic determination of physical properties and salt fluxes from sea ice. I argue that existing models are likely to overestimate substantially the peak buoyancy forcing of the polar oceans. |
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