Lagrangian decomposition of the Deacon Cell

The meridional overturning cells in the Southern Ocean are decomposed by Lagrangian tracing using velocity and density fields simulated with an ocean general circulation model. Particular emphasis is given to the Deacon Cell. The flow is divided into four major components: (1) water circling around Antarctica in the Antarctic Circumpolar Current (ACC), (2) water leaving the ACC toward the north into the three world oceans, (3) water coming from the north and joining the ACC, mainly consisting of North Atlantic Deep Water (NADW), and (4) interocean exchange between the three world oceans without circling around Antarctica. The Deacon Cell has an amplitude of 20 Sv, of which 6 Sv can be explained by the the east-west tilt of the ACC, 5 Sv by the east-west tilt of the subtropical gyre, and the remaining 9 Sv by the differences of the slope and depth of the southward transport of NADW and its return flow as less dense water. The diabatic or cross-isopycnal Deacon Cell is only 2 Sv.