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Keywords:

  • sea ice;
  • ocean-atmosphere flux

[1] Processes controlling the formation and transformation of frazil to pancake ice are examined using data from an array of drifting buoys deployed at the advancing ice edge in the Weddell Sea. A simple thermodynamic model is coupled to the buoy dynamics and to an ice redistribution model to determine the influence of deformation, thermodynamics, and mechanical scavenging, incorporating frazil crystals from the surrounding slick into the pancakes, on the partitioning of ice volume between frazil and pancakes. Ice production was examined from the time the buoys were deployed until the frazil/pancake cover consolidated into the more familiar pack ice. The model reproduced the expected ice cover thickness at consolidation (60 cm). Rafting was the dominant contribution to thickening in the region owing to large-scale compression of the initial area by northerly winds from passing low-pressure weather systems, which are rather typical in the region. High-resolution positional forcing from the buoys (20-min intervals) doubled the contribution of mechanical scavenging to final pancake thickness compared to the coarser (2-h) result, owing to the larger path length that the pancakes traverse through the frazil slick, and produced a significantly larger volume of ice in the pancake phase. The ice cover generated at consolidation was approximately twice as thick as would have formed by the more familiar congelation ice growth under the same forcing, reinforcing the importance of correctly parameterizing the early stages of ice formation in the Antarctic. The study highlighted uncertainties in the effect of the frazil/pancake cover on ocean-atmosphere heat exchange, both in terms of the area contributing to ice production and the effect on turbulent exchange coefficients. Further work placing the empirical parameters into a more constrained physical framework and introducing wave properties is suggested.