The Ocean's Meridional Oxygen Transport

Quantification of oxygen uptake at the ocean surface and its surface-to-interior pathways is crucial for understanding oxygen concentration change in a warming ocean. We investigate the mean meridional global oxygen transport between 1950 and 2009 using coupled physical-biogeochemical model output. We introduce a streamfunction in latitude-oxygen coordinates to reduce complexity in the description of the mean meridional oxygen pathways. The meridional oxygen transport occurs in two main cells: (a) the Northern Cell, dominated by the Atlantic Meridional Overturning Circulation, is nearly adiabatic in the Northern Hemisphere, and transports well oxygenated waters equatorward; (b) The Southern Cell, strongly diabatic, is shaped by the circulation in the Indo-Pacific basin, and combines the subtropical and abyssal meridional circulation cells when represented in depth-latitude coordinates. Analysis of isopycnal meridional oxygen transport shows that the northward flow from the Southern Ocean transports well oxygenated waters within intermediate and bottom layers, while oxygen-rich waters reach the Southern Ocean within deep layers (27.6 < sigma(0) < 27.9 kg m(-3)), carried by the North Atlantic Deep Water (NADW). This oxygenated NADW loses around 25% of its oxygen concentration along its meridional journey from the North Atlantic (at 55 degrees N) to the Southern Ocean. These insights into the oxygen dynamics as driven by the meridional overturning circulation provide a new framework for future studies on ocean deoxygenation.