Articles | Volume 7, issue 3
Ocean Sci., 7, 293–304, 2011
Ocean Sci., 7, 293–304, 2011

Research article 06 May 2011

Research article | 06 May 2011

Flow and mixing near a glacier tongue: a pilot study

C. L. Stevens1, C. L. Stewart1, N. J. Robinson1,2, M. J. M. Williams1, and T. G. Haskell3 C. L. Stevens et al.
  • 1National Institute for Water and Atmospheric Research (NIWA), Greta Point Wellington, New Zealand
  • 2University of Otago, Dunedin, New Zealand
  • 3Industrial Research Ltd. (IRL), Gracefield Lower Hutt, New Zealand

Abstract. A glacier tongue floating in the coastal ocean presents a significant obstacle to the local flow and so influences oceanic mixing and transport processes. Here acoustic Doppler current profiler and shear microstructure observations very near to a glacier tongue side-wall capture flow accelerations and associated mixing. Flow speeds reached around 40 cm s−1, twice that of the ambient tidal flow amplitude, and generated vertical velocity shear squared as large as 10−5 s−2. During the time of maximum flow, turbulent energy dissipation rates reached 10−5 m2 s−3, around three decades greater than local background levels. This is in keeping with estimates of the gradient Richardson Number which dropped to ~1 during maximum flow. Associated vertical diffusivities estimated from the shear microstructure results were substantial, reflecting the influence of the glacier on velocity gradients.