Characterizing horizontal thermal and salinity structure in the wake of a floating glacier
Alexander L. Forrest

Authors

A.L. Forrest¹, A. Hamilton², C.L. Stevens³ and B.E. Laval²

1. Australian Maritime College, University of Tasmania, Launceston, TAS, Australia
2. Department of Civil Engineering, University of British Columbia, Vancouver, BC Canada
3. Marine Physics, National Institute of Water and Atmospheric Research, Greta Point, Wellington, New Zealand

Abstract

Water column variability in the lee of the floating Erebus Glacier Tongue (EGT) was quantified using instrumented moorings, profilers and an Autonomous Underwater Vehicle (AUV). At the time of the work in 2011, the glacier extended 12 km into Southern McMurdo Sound, Antarctica. Vertical variability within the background tidal flows of ~0.3 m s^-1 was quantified using a combination of CTD and time series of flow characteristics from acoustic Doppler current profilers (ADCPs). These instruments were deployed at 3 locations along the main AUV transect. Horizontal variability in temperature and conductivity was measured over ~500m transects using a Conductivity-Temperature-Depth profiler mounted on the AUV, enabling wavenumber energy spectra to be estimated at 10, 25 and 50 m depths through a range of tidal conditions. Analyses show highly energetic mixing in the near-surface layer (i.e., at the two shallow most depths run by the AUV) in the wake of the EGT. The spectral magnitude at high wavenumber increased with regional flow speed. In some cases a clear isotropic turbulence regime was apparent (k ^-5/3). The turbulence characteristics identified in the AUV transects were comparable with the moored data at similar depths run by the AUV during both spring and neap tides. These results suggest that floating ice tongues contribute to enhanced energy dissipation in the near-surface layer. Furthermore, there are a number of features in common with the calving face of ice-shelves so that the results here promote a greater understanding of ice-ocean interactions in general.