Schematic of the Meridional Overturning Circulation (MOC).
Schematic of the Meridional Overturning Circulation (MOC). ©

The Meridional Overturning Circulation (MOC) is a large-scale oceanic process by which heat is transported from equatorial regions to the poles and is a critical regulator of Earth's climatic processes.

Huge ocean currents driven by a combination of factors including wind forcing, transport heat towards the poles. Here, processes such as heat loss to the atmosphere and sea ice formation lead to an increase in density and eventual sinking of surface waters.

These cold, dense waters flow away from the poles as deep ocean currents and play an essential role in the ventilation of, and provision of nutrients to, deep waters. The MOC is also important for the removal of carbon from the atmosphere as atmospheric carbon dissolves in surface waters and is transported to the deep ocean by the overturning process.

Due to its influence on the Earth's climate, it is crucial that climatic models represent the MOC realistically. However this presents a challenge as it is affected by numerous processes, such as internal ocean mixing, that can be difficult to understand. Climate model outputs have shown the MOC to be extremely sensitive to how mixing processes in the Southern Ocean are represented. It is therefore essential to improve our understanding of these processes so that model representations are as realistic as possible.

The DIMES project aims to increase our understanding of Southern Ocean mixing and thereby improve the manner in which this is modeled. This is expected to improve the models' representation of the MOC and thus increase the reliability of global climate predictions.

Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES)