Callaghan Innovation Research Papers

Back to Research Papers

TitleObservations of turbulence beneath sea ice in southern McMurdo Sound, Antarctica
Publication TypeJournal Article
Year of Publication2009
AuthorsStevens, C.L., Robinson N.J., Williams M.J.M., and Haskell T.G.
JournalOcean Science
Pagination435 - 445
Date Published2009
ISSN18120784 (ISSN)
KeywordsAntarctica, baroclinic motion, Buoyancy, deep water, diffusivity, dissipation, East Antarctica, ice crystal, ice shelf, isotropy, McMurdo Sound, Sea ice, supercooling, turbulence, vertical mixing, Water column
AbstractThe first turbulence profiler observations beneath land fast sea ice which is directly adjacent to an Antarctic ice shelf are described. The stratification in the 325m deep water column consisted of a layer of supercooled water in the upper 40m lying above a quasi-linearly stratified water column with a sharp step in density at mid-depth. Turbulent energy dissipation rates were on average 3×10 -8 m 2 s -3 with peak bin-averaged values reaching 4×10 -7 m 2 s -3. The local dissipation rate per unit area was estimated to be 10mWm -2 on average with a peak of 50mWm -2. These values are consistent with a moderate baroclinic response to the tides. The small-scale turbulent energetics lie on the boundary between isotropy and buoyancy-affected. This will likely influence the formation and aggregation of frazil ice crystals within the supercooled layer. The data suggest that the large crystals observed in McMurdo Sound will transition from initial growth at scales smaller than the Kolmogorov lengthscale to sizes substantially (1-2 orders of magnitude) greater than the Kolmogorov scale. An estimate of the experimentaveraged vertical diffusivity of mass Kρ yields a coefficient of around 2×10 -4 m 2s -1 although this increased by a factor of 2 near the surface. Combining this estimate of Kρ with available observations of average and maximum currents suggests the layer of supercooled water can persist for a distance of ∼250 km from the front of the McMurdo Ice Shelf. © Author(s) 2009.

Back to top