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SUMMARY:Salt fluxes from sea ice: simple models of reactively dissolved ch
 annels - David Rees Jones (University of Oxford)
DTSTART:20160609T134500Z
DTEND:20160609T143000Z
UID:TALK66409@talks.cam.ac.uk
CONTACT:INI IT
DESCRIPTION: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 permea
 ble ice matrix through which the brine can flow. Compositional convection 
 drives fluid motion within porous sea ice. The convective circulation lead
 s to the development of so-called &#39\;brine channels\,&#39\; liquid chan
 nels formed by a dissolution reaction. I discuss the physical mechanisms t
 hat create and sustain these channels. Some aspects of these mechanisms ma
 y apply to reactive channelization of magmatic flow through the mantle ben
 eath mid-ocean ridges\, for example.<br><br>Salt fluxes through brine chan
 nels are an important buoyancy forcing for the polar oceans\, with implica
 tions 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 ch
 annel size\, and salt fluxes. I test my predictions by considering previou
 s laboratory observations of the propagation of dye fronts within the ice 
 and salt fluxes from it. Finally\, I take a one-dimensional\, thermodynami
 c sea-ice model of the kind currently used in coupled climate models and p
 arameterize porous convection within a one-dimensional model. The paramete
 rization allows dynamic determination of physical properties and salt flux
 es from sea ice. I argue that existing models are likely to overestimate s
 ubstantially the peak buoyancy forcing of the polar oceans.
LOCATION:Seminar Room 1\, Newton Institute
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