We have understood for a long time that the oceans played a significant role in transferring heat from the equator to the poles, but only in recent years have we begun to understand the importance of the link between ocean and atmosphere.
The ocean and atmosphere are both important media to move heat from the equator to the poles. Because of the high specific heat of water, the ocean is the most massive reservoir of heat energy — 1,000 times greater than the atmosphere.
Since the atmosphere is transparent to visible light from the sun, most heating of the ocean is at the surface, which then heats the atmosphere above it. Density-driven mixing moves the heat by convection in both the atmosphere and the oceans, in patterns complicated by Earth’s rotation and the presence of continents.
This is “sensible” heat because it relates directly to temperature.
Energy in evaporating water stays with the water vapor in the form of latent heat — latent because it is hidden from temperature changes. Individual water molecules store the energy in the form of vibrations, or rotations of the three atoms that comprise the molecule. Condensation will eventually release the latent heat into the atmosphere at a different location, efficiently transferring the heat.
So on one hand, the oceans distribute heat slowly through currents of dense water that have high specific heat. On the other hand, the atmosphere distributes heat quickly with fast winds that have low specific heat but lots of latent heat.
Net gain from solar radiation is greatest at the equator and diminishes toward both poles. Net loss by infrared radiation to space is greatest at the poles and diminishes toward the equator. Over time, net gain balances net loss or else Earth’s temperature would either increase or decrease. The fluid movement of atmosphere and ocean is Earth’s way of moving heat poleward to keep the energy balance.
Earth-orbiting satellites have measured the division between regions of net gain and net loss of energy. Below 35 degrees latitude there is net gain, at higher latitudes there is net loss.
But nothing is so simple in this unbelievably complex and complicated system.
On a short time scale there are imbalances in heat flow as evidenced by moving weather systems, pockets of warm water that are not necessarily in the right place, such as the blob of warm water in the Eastern Pacific, and oscillating air/sea systems such as the El Nino Southern Oscillation, Pacific Decadal Oscillation, North Atlantic Oscillation and others.
Previously, meteorologists studied the circulation of the atmosphere in hopes of providing weather personnel with better tools for prediction. Now we understand that oceanic and atmospheric interactions affect weather and both short-term and long-term climate.
The Earth’s weather and climate systems and patterns evolve from the interactions and movements of heat and temperature at the surface of and deep in the oceans, and in the lower and upper atmosphere.
Overall, global weather and climate both influence and are influenced by temperature differences and the resulting heat flow of sensible and latent heat.
Richard Brill is a professor of science at Honolulu Community College. His column runs of the first and third Friday of the month. Email questions and comments to brill@hawaii.edu.
