Laboratory experimental study of water drag force exerted on ridge keel

With the diminishing Arctic sea ice, the dynamic energy-exchange process between sea ice and ocean gains in importance. Concerning how the ice bottom topography affects the drift of sea ice, it is unclear how the ridge–keel-drag force exerted by seawater changes the momentum balance of sea ice. We thus conducted laboratory experiments to investigate how the local drag coefficient of the ridge keel depends on keel shape and on the relative velocity of ice with respect to seawater. A dimensional analysis is used to obtain the relationship between the local drag coefficient Cr, the Reynolds number Re, the dimensionless keel depth h0, and the keel slope angle φ. The results indicate that the local drag coefficient Cr is only relevant to Re when Re < 4000 and the flow is in the laminar regime. With increasing Re, Cr depends on h0 and φ, which are independent variables, as the flow transitions to the turbulent regime. The parameterization formulas for Cr are also provided.