Coherent non-dispersive structures are known to play a crucial role in explaining transport in
non-autonomous dynamical systems such as ocean flows. These structures are difficult to extract
from model output as they are Lagrangian by nature and not revealed by the underlying Eulerian
velocity fields. In the last few years heuristic concepts such as finite-time Lyapunov exponents
have been used in an attempt to detect barriers to oceanic transport and thus identify regions that
trap material such as nutrients and phytoplankton. In this letter we pursue a novel, more direct
approach to uncover coherent regions in the surface ocean using high-resolution model velocity data.
Our method is based upon numerically constructing a transfer operator that controls the surface
transport of particles over a short period. We apply our technique to the polar latitudes of the
Southern Ocean. The coherent regions we identify appear to be located in the vicinity of major
gyres such as those in the Weddell and Ross Seas.