by Dale Allen Pfeiffer
Large bodies of water — particularly the oceans and seas — have a moderating effect upon the weather. As anyone living on an island or near the seashore is well aware, the summers in such an area tend to be cooler than farther inland, and the winters tend to be warmer. As a resident of the state of Michigan, I am well aware that an Alberta clipper which will freeze North Dakota and Minnesota down to -20º F, will be warmed sufficiently upon crossing over Lake Michigan so that this same weather system will only drop Michigan ‘s temperature down to 0º F. This is because bodies of water tend to have less seasonal variance in their temperature than does stone or soil, and they interact with overriding air masses to transfer heat from one to the other.
This process is much more complex in the oceans than in the Great Lakes. Ocean currents channel warm water from the equator and cold water from the polar regions, with considerable effect upon local weather. Warm waters flowing up from the South Pacific bring heat to the Pacific Northwest and the Alaska Panhandle through the winter, leading directly to the temperate rainforests which dominate the ecology of this area.
Meteorologists have traditionally ignored the oceans’ role in meteorological processes. And this would seem to make sense on the face of it: if you are studying the weather it is natural to focus on the atmosphere, not the oceans. But we are coming to understand that the oceans are an equal partner with the atmosphere in producing the weather, and the dominant partner with regard to long-range weather patterns.