What shipwrecks tell us about hurricanes

The heyday of piracy in the Caribbean in the 17th century coincided with a time of fewer hurricanes, according to a new study that uses shipwrecks and tree-rings to build a picture of conditions from the 1500s on.

The world-first research conducted at the University of Arizona compared records of shipwrecks with tree-ring data to identify a 75% reduction in hurricane activity in the Caribbean between 1645 and 1715. 

The researchers hope the discovery will assist experts in predicting weather patterns in the region.

The study is the first of its kind, says lead author Valerie Trouet, an associate professor at the University of Arizona Laboratory of Tree-Ring Research.

“By combining shipwreck data and tree-ring data, we are extending the Caribbean hurricane record back in time and that improves our understanding of hurricane variability,” says Trouet.

The researchers were keen to identify specific hurricane data from the past few hundred years, to better understand how weather patterns might be affected as the climate warms.

Grant Harley, associate professor at the University of Southern Mississippi and co-author of the paper, was able to map hurricane activity back to 1707 using tree-rings, because hurricane events impact the growth of trees.

Along with co-author Marta Domínguez-Delmás of the University of Santiago de Compostela in Spain, the three researchers compared tree-ring data with the wood from shipwrecks found along the Caribbean.

The data from the tree-rings, and the storm record by dating the wood from the shipwrecks, showed a correlation in hurricane events during these centuries. These overlaps were then compared with data from ship logs, and recordings of hurricanes between 1800 and 2009, all of which appeared to line up.

Once patterns in the weather events were uncovered, the significant dip in hurricane events became apparent. The lull appeared to occur between 1645 and 1715, a time period known as the Maunder Minimum, a time of lower temperatures in the Northern Hemisphere and roughly the same period known as the “golden age of piracy“.

The cooling is believed to have occurred because the Earth received less solar radiation at this time, as a result of lower sunspot activity.

“We didn’t go looking for the Maunder Minimum, it just popped out of the data,” says Trouet.

Identifying a link between cooler temperatures and fewer hurricanes could play an important role in predicting how our changing climate could impact hurricane activity, according to the researchers.

The research was published this month in The Proceedings of the National Academy of Sciences.