  The ability of viscous layer models to describe the attenuation of waves
propagating in grease-pancake ice covered ocean is investigated. In particular,
the Keller's model Keller [1998], the two-layer viscous model [De Carolis and
Desiderio 2002] and the close-packing model [De Santi and Olla 2017] are
extensively validated by using wave attenuation data collected during two
different field campaigns (Weddell Sea, Antarctica, April 2000; western Arctic
Ocean, autumn 2015).
  We use these data to validate the three models by minimizing the differences
between the measured and model wave attenuation; the retrieved ice thickness is
then compared with measured data.
  The three models allow to fit the observation data, but with important
differences in the three cases. The close-packing model shows good agreement
with the data for values of the ice viscosity comparable to those of grease ice
in laboratory experiments. For thin ice, the Keller's model performance is
similar to that of the close-packing model, while for thick ice much larger
values of the ice viscosity are required, which reflects the different ability
of the two models to take into account the effect of pancakes. The improvement
of performance over the Keller's model achieved by the two-layer viscous model
is minimal, which reflects the marginal role in the dynamics of a finite eddy
viscosity in the ice-free layer. A good ice thickness retrieval can be obtained
by considering the ice layer as the only source in the wave dynamics, so that
the wind input can be disregarded.
