The ocean is curiously cold. Even in regions where surface temperatures are at a maximum, the average temperature of a water column is barely above the freezing point. The reason is the shallowness of the thermocline, the interface between the layer of warm surface water and the much colder deep abyss. So shallow is the thermocline that a change in its slope, because of a change in the winds, alters sea surface temperature patterns. Those patterns in turn affect the winds. This circular argument – the winds are both the cause and consequence of surface temperature changes – imply unstable ocean-atomsphere interactions that give rise to phenomena such as El Niño and La Niña. One of my research interests concerns those interactions.
Why is the ocean so cold? What processes determine the thermal structure of the ocean? The answer is of vital importance for a variety of reasons, including the possibility that a deepening of the thermocline, in response to global warming for example, can result in permanent El Niño conditions. We are developing models to explore this possibility, but how will we check the results? Some of the very different climates the Earth has experienced during its long history probably involved changes in the thermal structure of the ocean. (The Earth was far colder than it is today during the last Ice Ages some 20,000 years ago. It was far warmer than today some three million years ago.) These are the reasons for my interest in paleo-climates.