Airflow driven pinch-off of a bubble in a rotating liquid

We create air bubbles at the tip of a ``bathtub vortex'' which reaches to a finite depth. The ``bathtub vortex'' is induced by letting water drain through a small hole at the bottom of a rotating cylindrical container. The tip of the needle-like surface depression is unstable at high rotation rates and releases bubbles which are carried down and out through the drain-hole. Using high-speed imaging we find that the minimal neck radius of the unstable tip decreases as $R(t) \sim t^{\frac{1}{3}}$. This power law exponent signals that the air flow in the neck becomes the dominant effect over the stabilizing centrifugal forces and causes the eventual pinch-off.