How tree rings help make a case that a 19th century shipwreck in Argentina could be a ship built in Warren, R.I.

“I was really excited,” said researcher Ignacio Mundo. “The last ring corresponds to 1849, and knowing the Dolphin was launched in 1850 — you say, okay, we are really close.”

Ignacio Mundo of Argentina’s Laboratory of Dendrochronology and Environmental History measures one of the ribs of the Patagonian wreck known as Bahía Galenses, in preparation for sampling.Courtesy of Mónica Grosso

PROVIDENCE — For years, researchers have suspected that a shipwreck in the shallow waters off Argentina started its seafaring journey about 10,000 miles away, in Warren, Rhode Island.

But the world of archaeology is a cautious one, perhaps especially in maritime archaeology, where artifacts are not just old, but waterlogged and nibbled away by marine species with names like shipworms and gribbles. Nobody could say for sure whether a ship called the Dolphin, built in the East Bay of Rhode Island in 1850 before voyaging across the globe to hunt whales, had ended up as the Patagonian wreck now known as Bahía Galenses.

So researchers turned to dendrochronology — the dating of objects by the growth rings in timber — and a chainsaw. They cut off parts of the shipwreck, then put them under a microscope, measuring their rings to the nearest 0.001 millimeter. Drought cycles imprint a sort of barcode on trees’ rings, which can help identify not just where a piece of wood came from, but when. The latest date researchers found a tree had been cut to construct parts of the ship? 1849. The very next year, historical records say, the Dolphin was built and launched.

“I was really excited,” said Ignacio Mundo, of Argentina’s Laboratory of Dendrochronology and Environmental History. “The last ring corresponds to 1849, and knowing the Dolphin was launched in 1850 — you say, okay, we are really close.”

The findings of Mundo and other tree ring experts and archaeologists in Argentina and at Columbia University in the United States, were published in a study this month in the journal Dendrochronologia.

This new evidence linking the shipwreck to Warren is still not enough to definitively prove the wreck is Rhode Island’s Dolphin, the maritime archaeologists involved in the research say.

“The results of the analysis performed on wood samples from this shipwreck are consistent with the date and place of construction of the Dolphin, but could also be consistent with other ships of the same period and origin,” Cristian Murray and Mónica Grosso, co-authors and researchers at Argentina’s National Institute of Anthropology and Latin American Studies, said in a written statement. “Therefore, we say that this dendrochronological study significantly narrows the range of possibilities but does not constitute conclusive evidence.”

Some of the tree ring experts involved in the work, on the other hand, are more convinced.

“It was incredible, to have that exact year,” said Mukund Palat Rao, a postdoctoral research scientist at Columbia’s tree ring laboratory who was another co-author on the study. “Having that calendar year match up so perfectly with the construction of this ship — that was really great, to have that evidence from the trees.”

The history of the Dolphin helps chart the history of whaling in general, and Rhode Island in particular. Its first voyage, which took two and a half years, crossed the Atlantic and Indian oceans for whale oil. Other destinations included the Seychelles, Zanzibar, and Australia, according to an account published by Columbia University. In October 1858, the ship set out from Warren again, but wrecked in Argentina the next year when it “lay upon the rocks in the southwestern part of New Bay,” the ship’s master reported to the owners.

Almost a century and a half later, shifting sands in an intertidal area of Golfo Nuevo started to expose the remains of a ship in the same area where the Dolphin was believed to have wrecked. Archaeologists eventually found cast-iron pots, probably the “try-works” to boil whale blubber for oil. Because of the striking similarities, for at least a decade, experts had hypothesized that the wreck might be the Dolphin.

There was nothing definitive, though — no bell with the name “Dolphin” on it.

But there was plenty of wood. And trees, as anyone who went through a primary school science class might recall, have rings that show how old they are. Those rings tell a deeper, more specific story than just the tree’s age: How much did the tree grow that year? Was it a hot season, or a cold one? A wet or a dry one? Was the tree happy and healthy and well fed, or thirsty and stressed out? And because of regional differences in climate, you can also ask: Where did it grow?

Dendrochronology can be used on wood from shipwrecks and buildings alike. A few years ago, Mundo convinced his archaeological colleagues that they should cut off parts of the shipwreck for this sort of precise analysis.

That’s where the chainsaw came in. The preservation-minded archaeologists were reluctant, Mundo said. But the data can be very telling: You can take timbers whose age and origin you want to know, and compare them to a huge database of trees whose age and origin you do know. You can also tell whether they were alive at the same time. And from there you can work backward from the tree whose age you do know to find the year when the tree was chopped down to make the timber of your shipwreck. It’s sort of like matching fingerprints or comparing the grooves on two different bullets to see if they were fired from the same gun.

But first you need a really good data set. Columbia University has one: The North American Drought Atlas. The Patagonian shipwreck was suspected of being a whaling ship of North American vintage, so the database would come in handy. Mundo teamed up with the experts at Columbia Climate School’s Lamont-Doherty Earth Observatory to analyze the tree rings and compare them to the data in the drought atlas. From there, they were able to date two tree species from the wreck: yellow pine, and white oak.

A cross section of one of the wreck's oak ribs – specifically a first futtock. This sample had 156 rings; its last ring was dated 1845. Holes in upper part were made by wood-eating marine worms. Courtesy of Ignacio Mundo

A cross section of a hull plank made of yellow pine. The upper image shows the raw sample; the lower image, after sanding to make tree rings stand out. This sample contained 258 annual rings.Courtesy of Ignacio Mundo

The yellow pine was more ambiguous, dating to 1810 in the southeastern United States. But the pine was used in planks, with more of its rings sheared off in the process of milling it.

The oak sampling yielded more helpful information. The shipwreck timbers closely resembled tree samples from Pennsylvania, New Jersey, New York, and in particular Massachusetts, with simultaneous periods of low growth in the 1680s, 1690s, 1700s and 1810s.

The team of researchers was also able to determine the latest year when oak was cut to produce wood for the ship that wrecked in Argentina. The oak samples were taken from the futtocks, or the lower part of the ship’s frame. They were a little more raw, a little less processed than the pine. Some oak samples still had the “waney edge,” or the very outermost rings near where the bark is. Because of that, they could see exactly when the rings had stopped — due, obviously, to the tree being cut down. From there they got a year: 1849.

So, the wood could have made its way from New York or Massachusetts to Rhode Island to build the Dolphin in Warren. Although that would have been a pretty quick turnaround time for timber seasoning, records suggest that the Dolphin’s builders were in a hurry. According to research by Warren historian Walter Nebiker, citing a contemporary report in The Northern Star newspaper, builders laid the Dolphin’s keel in August 1850, and it was launched 99 days later.

“I’ve got absolutely no doubt about the dating being correct here,” said Edward Cook, the director of Columbia’s tree ring laboratory and a co-author of the study.

The link highlights Rhode Island’s rich maritime history, which is said to have more shipwrecks per square mile than any other state — but also sent a lot of ships elsewhere, too. That can prompt the sort of remark that will make you groan if you hear it too much but nevertheless remains true: It’s called the Ocean State for a reason. And it played an outsize role in maritime trade. Maybe all the way to Patagonia.

“It just tells us how interconnected we have been for a really long time,” said Rao, the Columbia researcher. “And it tells us a lot about human history, and our history of navigation. It’s still very relevant as the world becomes even more interconnected.”