Sea ice is a two-phase medium comprising
solid ice crystals and liquid, interstitial
brine.  It is a porous medium: the brine
can flow in response to external pressure
forces and internal buoyancy.  Predictions of
the spatial distribution and temporal
evolution of both the sea-ice thickness and
the local volume fraction occupied by ice
crystals can be made using thermodynamic
models once the local bulk salinity is known
or assumed.  The solid fraction determines not
only the thermodynamic properties of the sea
ice but also its permeability to flow.
However, any flow, by redistributing salt,
alters the local bulk salinity and, hence, the
solid fraction.  Thus there are complex
interactions between internal solidification
and fluid flow within sea ice.  These can, for
example, cause the formation of brine channels
(narrow, vertical channels of zero solid
fraction), which are the principal conduits
for brine drainage from undeformed sea ice to
the ocean.

I shall decscribe the coupled thermodynamics
and fluid dynamics of sea ice, combining
insights from laboratory experiments and
theoretical models, to address questions of
brine drainage from young sea ice, including
the formation of brine channels, their
fully-developed structure, and the fluxes
through them that ultimately determine the
bulk-compositonal profiles in addition to the
buoyancy delivered to the underlying ocean.