Official records of hurricane activity in the Atlantic didn’t being until 1851, so for years researchers relied on historical anecdotes as well as physical markers like coastal lake sediments or coral isotopes to fill in the timeline. Yet in a new study, scientists describe a more precise marker: shipwrecks.
To suss out the potential periods of increased cyclonic activity in the Caribbean, a team of researchers from Arizona State University examined data on 657 shipwrecks that the Spanish government recorded between 1495 and 1825, according to a press release from UANews.
They then compared these values to tree ring data since hurricanes commonly strip the trees of limbs and leaves, stunting growth.
“We found that in the years when many ships wrecked in the Caribbean, the trees in the Florida Keys showed the same signal that trees show during hurricanes,” an author of the new paper Valerie Trouet of the University of Arizona tells Jason Thomson at the Christian Science Monitor. “So, that gave an indication that we could use shipwreck records as a proxy for hurricane activity.”
It's important to note that tree rings alone cannot be used to determine past storms because many other conditions also influence the rate of tree growth. Together, however, the markers provide a more accurate measure than either can alone.
The new method of measuring hurricane activity helps scientists hone in on exactly when the storm struck, according to the new study published in the journal PNAS. Dates were previously estimated using lake sediments, which can be used to estimate when the storms struck within a century. The new method narrows this range down to 10 to 15 years and in some cases even annually.
The shipwreck and tree ring data also show a 75 percent decrease in hurricane activity between 1645 and 1715—a period known as the Maunder Minimum during which reduced sunspot activity resulted in cooler sea surface temperatures, Chris Mooney writes for The Washington Post. Though the causes of hurricanes can be complex, scientists generally believe that lower sea surface temperatures suppresses hurricane activity, Mooney writes.
UANews points out that while the research doesn’t lead to direct predictions about future hurricane activity, it does help scientists understand how changes in solar radiation, including those caused by greenhouse gases, affect the formation of the storms.
Allure of the new method also extends beyond climate research. “Historians are also interested,” Trouet tells the Christian Science Monitor. “This was a period of lots of historical change in the Caribbean, as well as slavery and piracy. Is there a link between low hurricane activity and historical events or trends?”
With the new method already in their sights, it will hopefully be smooth sailing to find an answer.