  Irregular, unidirectional surface water waves incident on model ice in an ice
tank are used as a physical model of ocean surface wave interactions with sea
ice. Results are given for an experiment consisting of three tests, starting
with a continuous ice cover and in which the incident wave steepness increases
between tests. The incident waves range from causing no breakup of the ice
cover to breakup of the full length of ice cover. Temporal evolution of the ice
edge, breaking front and mean floe sizes are reported. Floe size distributions
in the different tests are analysed. The evolution of the wave spectrum with
distance into the ice-covered water is analysed in terms of changes of energy
content, mean wave period and spectral bandwidth relative to their incident
counterparts, and pronounced differences are found between the tests. Further,
an empirical attenuation coefficient is derived from the measurements and shown
to have a power-law dependence on frequency comparable to that found in field
measurements. Links between wave properties and ice breakup are discussed.
