= Iceberg towing drag
{title2=$F_D=\tfrac12\rho C_DAU^2$}
<Iceberg towing drag> is the water resistance that a towing force must overcome to move an <iceberg> relative to the surrounding water. A quadratic model is $F_D=\tfrac12\rho_w C_D A U^2$, where $U$ is the relative speed and $C_D$ must be defined using the same reference area $A$ as in its calibration.
For a form-drag coefficient, that area is commonly the submerged frontal area. A coefficient describing an equivalent basal resistance may instead use an immersed horizontal area. Interchanging the two conventions changes the force estimate. The $U^2$ dependence makes a modest increase in towing speed expensive, and currents can change resistance without changing the iceberg's speed over the ground.
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