Researchers at the University of York found proof that natural causes partly led to sea-level rises in the North American Atlantic coast during the 18th century.

Their research unraveled facts indicating that sea levels in Connecticut, Maine and Nova Scotia rose to about two (2) to three (3) millimetres every year at the height of the pre-industrial period. The findings indicate that increased rates in rise of sea levels is also part of the climate system’s natural processes.

Lead author of the study, Roland Gehrels, a professor in the Department of Environment and Geography at the University of York in England said, the earlier occurrences of rapid sea level rise during the 18th Century, was not a known fact before. Professor Gehrels explained that they found this out when they were establishing the base sea level from archival times.

Although the rate of the rise was slower when compared to the present, it was quicker than what the researchers had expected to have occurred at a time when the Arctic was relatively warm. Earlier climate scientists described that historical climate condition as “Little Ice Age,” a term referring to a cooling that transpired after the “Medieval Warm Period,” which extended between the 14th and 19th centuries.

Inasmuch as there were no human influences or anthropogenic forces during the pre-industrial years, the U of Y researchers surmised that the 18th century rapid rise in sea levels in North America’s northeast coast were results of a natural cause. In part, they were related to a see-saw of a large scale atmospheric pressure called the “North Atlantic Oscillation” and to the resulting increased ice melts during said periods.

According to Professor Gehrels, their goal was to find out how global warming affects present day sea levels. In the 20th century, levels had risen at rates of up three (3) or four (4) millimetres per year, faster than the rates exhibited in any century within the last 3,000 years, at the least.

Ramifications of the Fact that Sea Levels Rise as a Result of a Natural Cause

Since the 1950s, previous studies had already identified the North American Atlantic Coast as “hotspot” due to the noted higher-than-average rates of sea level augmentation. That being the case, Professor Gehrels warned that

”If the high rates exhibited in this hotspot, occur persistently and recurrently, they present significant potential threats for large centres of population.”

The U of Y professor added that when making plans for sea level rise, cities like Boston and New York should also take into consideration this natural variability. Using sea level reconstructions built from salt-marsh sediments and fossils derived from the Atlantic coast, the models showed that sea level rises will be considerably higher than the global average, by the 21st Century; particularly in areas like New York City.

This University of York study has been published in Geophysical Research Letters. Acknowledgments were given to the collaboration of the National Oceanography Centre in Liverpool and the Woods Hole Oceanographic Institution in Massachusetts; the Universities of Bangor, Durham and Leeds in the UK; as well as the Old Dominion University in Virginia, U.S.A. and the Siegen University in Germany.