An eastward flowing current, also known as the West Wind Drift, that circles Antarctica and extends from the surface to the ocean floor. With a volume transport of 130 Sv (130 × 106 m3s−1) it is the largest of all ocean currents. Current speed in the ACC is comparatively modest (0. 1 m s−1, but larger in fronts), the large transport being achieved by the current's great depth. Seventy-five percent of the transport occurs in the polar and subantarctic fronts that make up only 20% of the ACC area. Interannual variability is about 15% of the mean but can reach 40% on occasions. The ACC is influenced by bottom topography, which causes deflections from its general westward path and eddy formation, particularly at the Scotia Ridge, the Kerguelen Plateau, and the Macquarie Ridge. The eddies are instrumental for the poleward transport of heat across the current, which would otherwise block meridional heat transfer.