Dear Tom,
Why do tides vary so much depending upon location?
Rich Pokorski, Morton Grove, Ill.
Dear Rich,
In the big picture, astronomical factors affect the magnitude of the Earth’s tidal bulges, but on a smaller scale the size of the tides are strongly influenced by the shape of the shoreline and the nature of the underwater transition from deep ocean to land. Funnel shaped bays that become narrower and shallower can dramatically alter tides. A classic example is the Bay of Fundy in Nova Scotia, which boasts the world’s highest tides, varying by more than 50 feet. In contrast, narrow inlets and shallow water areas, like Laguna Madre which separates Padre Island from the Texas mainland and Pamlico Sound in North Carolina, tend to dissipate incoming tides and are often classified as non-tidal even though they have ocean inlets.
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Tom Skilling is chief meteorologist at WGN-TV. His forecasts can be seen Monday through Friday on WGN-TV News at noon and 9 p.m.
Write to: ASK TOM WHY, 2501 Bradley Pl., Chicago, IL 60618 or asktomwhy@wgntv.com (Mail volume precludes personal response.)
