The ebb and flow of ocean tides is a phenomenon that generally is considered one of the most predictable on Earth. But in reality the scope of the tides varies considerably with the passage of long periods of time, in ways that have not been properly taken into account in most assessments of changes in the level of prehistoric seas.
Due to phenomena such as ice ages, plate tectonics, the processes of land elevation, erosion and sedimentation, the tides have changed dramatically through the millennia, and may change again in the future, as is revealed a new study conducted by the team of David Hill (Oregon State University).
Some tides on the East Coast of the United States, for example, could be several times the past much greater than today, presenting a difference between high tide and low of 3 to 6 meters, instead of the current 1 to 2 meters on average.
Instead, the tides in the Bay of Fundy, which today are among the most extreme in the world and reach a range of up to 17 meters, were not a big deal about 5,000 years ago. However, approximately the same time, the tides in the South Atlantic coast in the U.S., North Carolina to Florida were 75 percent larger.
The research, based largely on high-resolution digital simulations, scientists have worked at Oregon State University, the Pennsylvania and Tulane in the U.S., as well as Leeds in the UK, and Toronto in Canada.
One of the most interesting findings of the study is about 9,000 years ago, when Earth was emerging from its most recent ice age, there was a large amplification of the tides in the western Atlantic Ocean. The tidal range was up to three times greater than that today.
Many other factors can also affect the tides, and a good knowledge of these factors and their effects is essential to get key information about past sea levels and ocean dynamics, an issue of concern for a second start since current global warming will also cause changes in sea levels.
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