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| Titel |
Experimental observations of the transport of brine and dissolved gases in sea ice |
| VerfasserIn |
Ceri A. Middleton, Carelle Thomas, Darío M. Escala, Anne De Wit, Jean-louis Tison |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250098837
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| Publikation (Nr.) |
 EGU/EGU2014-14553.pdf |
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| Zusammenfassung |
| A detailed knowledge of processes in sea ice is necessary to understand how sea ice
behaviour both affects and is affected by our changing climate. As the extent of sea ice cover
is modified due to anthropogenic climate change, it is important to understand how these
variations will themselves contribute to feedback mechanisms in the climate system,
particularly when considering the sources, sinks, and transport of CO2 and other climatically
important gases.
So that we can understand the effect that changing sea ice cover will have on the amount
of CO2 in the atmosphere and the oceans, we have to understand how gas transport occurs in
sea ice. It is therefore necessary to understand the movement of the brines in which these
gases are dissolved.
The mechanisms of sea ice formation have been well described previously, however, the
processes and mechanisms of transport of brine and fresher sea water through the ice are not
yet completely understood. As ice freezes from sea water, it behaves as a mushy
layer in which the salts present are expelled into pockets of increasingly saline
brine. These pockets link together at certain critical values of brine volume fraction,
temperature, and salinity to form channels by which the dense brine can sink into the
underlying sea water, so driving convective transport from the ice layer into the
sea.
To analyse the influence of this convection on the transport of gases in ice, we will
experimentally characterise convective patterns and instabilities in an ice-liquid two-layer
system. We produce a quasi-2D ice-salt water interface within a Hele-Shaw cell by applying a
gradient of temperature to a thin layer of saline water, cooling from the upper boundary. As
the system cools, a freezing front develops, so forming a 2D model of the mushy
layer.
Here we will present the methodology and preliminary results of visualisation of this
process using optical imaging techniques. Schlieren and synthetic Schlieren imaging allow
gradients of densities to be mapped due to their different refractive indices, and we can
therefore potentially observe the downward flow of denser brine and upward movement of
fresher water as the freezing front progresses. From these experiments we can provide
qualitative observations of the transport mechanisms, and also analyse the onset of convection
within these brine channels. |
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