Acadia National Park - FLOW: Sea - Air Exchange

The zone of contact where the lower surface of the atmosphere interacts with the upper surface of the ocean may seem to be of negligible thickness. Yet the exchange between these two bodies--one gaseous, one liquid--is crucial to the formation of ocean currents, winds, weather, and other earthshaking events. And when it comes to storm formation, this is where torrents meets the waves.

Most of the energy input driving atmospheric circulation comes from contact with earth"s surface. The ocean"s heat-storage capacity is much greater than that of either land or air. Given that the specific heat capacity (the ability to absorb or lose heat without changing temperature) of water is more than four times that of air, and considering that only the 70 m deep top layer of the ocean can be mixed, this top layer of the ocean alone can store about thirty times more heat than the entire atmosphere can.

What does that mean? For the same increase or decrease in energy, the atmosphere"s temperature change will be thirty times greater than the ocean"s. This explains the "moderating effect" of the ocean on nearby land. In the summertime, seaside towns are almost always cooler and breezier than non-coastal areas. The ocean"s ability to store heat also keeps seaside areas warmer in winter so that snowfall is often less and temperatures generally milder than conditions inland. Watch out for sea squalls and fog, though! When the ocean and atmosphere are at markedly different temperatures, storms or heavy fog can be spawned in the air-sea contact zone. Winds, storms, fog, rain, and clouds are all results of the dramatic interaction between the air, sea, and the sun"s energy.

What is exchanged in the boundary layer where air and oceans meet? The atmosphere is the source of carbon dioxide and oxygen dissolved in marine waters. Too, nitrogen, and iron enter saltwater from the air, as do windblown dust and a variety of air pollutants contributed by human activities. The exchange of carbon dioxide between air and ocean is crucial in regulating Earth"s climate and temperature.

What does the atmosphere receive from the world ocean? Water vapor, for sure. Which affects the temperature and humidity of the lower atmosphere. It now appears that marine life affects emissions of di-methyl sulfide, which oxidizes to produce condensation nuclei around which water droplets can form.

Concentration differences between substances in air and water affect the air-sea exchange, as do winds, currents, and turbulence in both fluids (yes, air is a fluid). The exchange of gases and energy at the interface between air and saltwater is extremely complex and little understood. One thing is clear: the exchange is a crucial regulator of the water cycle and has a powerful impact everywhere on Earth.

Like so many life processes, we don"t understand very well how air and saltwater interact, but we do know the interaction is essential to maintaining the integrity of planetary life.