Introduction

Energetics is one of the fundamental aspects of the climate system. Over the past decades many studies have been devoted to the energetics of the oceanic circulation. Although a more general definition of the oceanic general circulation may include wind-driven circulation, thermohaline circulation, and tides, the commonly used definition of oceanic general circulation is confined to the wind-driven circulation and thermohaline circulation.

Wind-driven circulation is a direct consequence of wind stress applied to the sea surface; therefore the energetics of wind-driven circulation must be closely linked to wind stress energy input. However, the cause of the thermohaline circulation seems complicated and remains the subject of hot debate. As explained shortly, the nature of the thermohaline circulation may depend on the viewpoint of the person who studies the problem. Therefore, research into the energetics of the oceanic circulation is often focused on the causes of the thermohaline circulation.

Energetic view of the ocean

Most previous studies on the energetics of the thermohaline circulation have been focused on the balance of thermal energy, in particular the air–sea heat fluxes and the meridional transport of thermal energy. A typical example is the book, Physics of Climate (Peixoto and Oort, 1992), in which the balance of thermal energy and its transformation have been discussed in great detail.

For a long time the importance of the mechanical energy balance, in particular energy sources from wind stress and tidal forces, failed to be recognized in the study of the thermohaline circulation.