Relating wave attenuation to pancake ice thickness, using field measurements and model results

Martin J Doble (1) , Giacomo de Carolis (2) , Michael H. Meylan (3) , Jean-Raymond Bidlot (4) , Peter Wadhams (5)

1 LOV - Laboratoire d'océanographie de Villefranche
2 CNR-IREA Milan
3 School of Mathematical and Physical Sciences
4 ECMWF - European Centre for Medium-Range Weather Forecasts
5 Department of applied maths and theoretical physics

Wave attenuation coefficients (α, m À1) were calculated from in situ data transmitted by custom wave buoys deployed into the advancing pancake ice region of the Weddell Sea. Data cover a 12 day period as the buoy array was first compressed and then dilated under the influence of a passing low-pressure system. Attenuation was found to vary over more than 2 orders of magnitude and to be far higher than that observed in broken-floe marginal ice zones. A clear linear relation between α and ice thickness was demonstrated, using ice thickness from a novel dynamic/thermodynamic model. A simple expression for α in terms of wave period and ice thickness was derived, for application in research and operational models. The variation of α was further investigated with a two-layer viscous model, and a linear relation was found between eddy viscosity in the sub-ice boundary layer and ice thickness.

Domaines: Géophysique [physics.geo-ph]; Géophysique [physics.geo-ph]

Martin J Doble, Giacomo de Carolis, Michael H. Meylan, Jean-Raymond Bidlot, Peter Wadhams. Relating wave attenuation to pancake ice thickness, using field measurements and model results. Geophysical Research Letters, 2015, 42 (11), pp.4473-4481 ⟨10.1002/2015GL063628⟩. ⟨hal-01166908⟩