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Implications of salt fingering processes for salt movement in thawed coarse-grained subsea permafrost
AbstractPore fluid velocities of vertical salt fingers, moving downward, in laboratory experiments with sands and thawed coarse-grained subsea permafrost sediments are on the order of 1 to 3 cm/hr with a maximum velocity of 5.6 cm/hr over distances of 0.1 to 0.4 m. It was demonstrated that fresh meltwater fingers move upward through a saline solution in thawed sand overlying a thawing phase boundary with frozen sand containing freshwater ice. Laboratory measurements of the hydraulic conductivity of thawed coarse-grained subsea permafrost sediments (silty sand) yield values about 103 times larger than values obtained in previous field measurements. The results of these laboratory experiments show that gravity-driven convection, in the form of salt fingering, can produce rapid salt movement in sands and in thawed subsea permafrost sediments. Field observations of coarse-grained subsea permafrost, including the relatively uniform salinity profiles in the thawed layer, the small change in salinity across the phase boundary, the boundary layer thickness, and the topography of the phase boundary, argue in favor of the larger values for hydraulic conductivity and pore fluid velocities suggested by these experiments. If these laboratory results are indicative of in situ conditions in subsea permafrost, then new interpretations of field observations and of previous modeling studies of coarse-grained subsea permafrost are required.
Implications of salt fingering processes for salt movement in thawed coarse-grained subsea permafrost
AbstractPore fluid velocities of vertical salt fingers, moving downward, in laboratory experiments with sands and thawed coarse-grained subsea permafrost sediments are on the order of 1 to 3 cm/hr with a maximum velocity of 5.6 cm/hr over distances of 0.1 to 0.4 m. It was demonstrated that fresh meltwater fingers move upward through a saline solution in thawed sand overlying a thawing phase boundary with frozen sand containing freshwater ice. Laboratory measurements of the hydraulic conductivity of thawed coarse-grained subsea permafrost sediments (silty sand) yield values about 103 times larger than values obtained in previous field measurements. The results of these laboratory experiments show that gravity-driven convection, in the form of salt fingering, can produce rapid salt movement in sands and in thawed subsea permafrost sediments. Field observations of coarse-grained subsea permafrost, including the relatively uniform salinity profiles in the thawed layer, the small change in salinity across the phase boundary, the boundary layer thickness, and the topography of the phase boundary, argue in favor of the larger values for hydraulic conductivity and pore fluid velocities suggested by these experiments. If these laboratory results are indicative of in situ conditions in subsea permafrost, then new interpretations of field observations and of previous modeling studies of coarse-grained subsea permafrost are required.
Implications of salt fingering processes for salt movement in thawed coarse-grained subsea permafrost
Baker, G.C. (author) / Osterkamp, T.E. (author)
Cold Regions, Science and Technology ; 15 ; 45-52
1987-10-20
8 pages
Article (Journal)
Electronic Resource
English
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