Laboratory experimental study was carried out to measure the flow velocity field under different kinds of floe models with smooth or rough bottom using Particle Image Velocimetry (PIV) technology. The disturbance depth z´ under the floe model was found to increase linearly with the geometric roughness of floe underside, namely the obliquity θ of serrate fluctuations on the model bottom. Profile analyses revealed that the roughness length z0, determined from the logarithmical profile, also increased linearly with θ. Influences of floe draft and initial flow velocity on z´ and z0 could be both ignored.
Sea ice drag coefficient is one of the most important parameters involved in sea ice dynamics, representing the momentum exchange between sea ice and atmospheric, oceanic boundary layers (Lepparanta, 2005). Parameterization of sea ice drag coefficient means to develop the relationship between drag coefficient and ice geometric parameters such as surface roughness, size, concentration and thickness by dividing the total drag force into different terms and combing with the influences from different factors (Lupkes and Birnbaum, 2005). Compared with the traditional calculation methods of drag coefficient (i.e. eddy correlation method, profile method, momentum method) (Ji et al., 2003), more specific physical mechanisms altering the drag force are contained in the parameterization method. Thus, the accuracy and feasibility of the coefficient can be improved, and further the results of sea ice dynamics numerical modeling can also be highly improved. Especially, few systemic field observations of the oceanic boundary layer under sea ice have been reported (eg. Shirasawa and Ingram, 1991a, b), in contrast to the abundant observations in the atmospheric boundary layer above ice (eg. Prinsenberg and Peterson, 2002), resulting in a lack of the understanding of many key processes involving in the dynamic interactions between sea ice and ocean.
