Hurricanes of unprecedented strength that slammed New England during the first millennium could come with grim predictions for the future.
A new record of sediment deposits from Cape Cod, Mass. revealed that 23 severe hurricanes hit the coast between the years of 250 and 1150, the American Geophysical Union reported. Most of these hurricanes were believed to be more intense than any that have been documented in that region in recorded history.
"These records suggest that the pre-historical interval was unlike what we've seen in the last few hundred years," said Jeff Donnelly, a scientist at Woods Hole Oceanographic Institution.
The researchers believe these prehistoric hurricanes were fueled by warmer sea surface temperatures in the Atlantic, which is a phenomenon that has been observed to be repeating itself today.
"We hope this study broadens our sense of what is possible and what we should expect in a warmer climate," Donnelly said. "We may need to begin planning for a category 3 hurricane landfall every decade or so rather than every 100 or 200 years. The risk may be much greater than we anticipated."
To make their findings, the researchers looked at sediment deposits from Salt Pond near Falmouth on Cape Cod. Over the past few centuries, strong hurricanes have swept sediments over the sand border separating the pond from the sea. The team extracted 30-foor-deep sediment cores from the pond, which were then analyzed in a laboratory. From these sediments, the researchers identified evidence of 32 prehistoric hurricanes, as well as large storms that occurred in the years 1635, 1675, and 1991 (Hurricane Bob).
The sediments revealed there were two periods of elevated hurricane activity on Cape Cod spanning between the years 150 and 1150, as well as between 1400 and 1675. The researchers believe these periods of intense hurricane activity link up with intervals of warm sea surface temperatures occurring during the same time periods. The researchers also noted ocean temperatures have been slowly rising in recent decades, and the tropical North Atlantic sea surface has already surpassed the warmth of prehistoric levels with no sign of stopping anytime soon.
"[The analysis] is really nice work because it gives us a much longer period perspective on hurricanes," said Kerry Emanuel, a professor of atmospheric science at the Massachusetts Institute of Technology in Cambridge. "It gives you something that you otherwise wouldn't have any knowledge of."
The findings were published in a recent edition of the journal Earth's Future.
