Each summer, young Kemp's ridley sea turtles follow the Gulf Stream north from the tropics to feed. Each fall, some number of those are caught off-guard by falling water temperatures and may wash ashore, dehydrated and paralyzed by cold. It's a story as old as Cape Cod, but it's been changing in recent years.
Most notably, the number of turtles that arrive on the beaches along Cape Cod Bay each fall has risen. The increase began in the 1990's, but there's been a dramatic jump in the past few years that . In 2012, rescue workers counted more than four hundred sea turtles, four to five times the average of previous years. In 2014, that record was smashed when more than 1,200 turtles stranded. This year's tally currently stands at just over five hundred thirty - a solid second place.
What's really remarkable about this year is the timing. The stranding season has typically begun in October or November, and wound up by the end of the year. This year's strandings didn't get going until December and now, in January, turtles - both alive and dead - are continuing to wash ashore. That, in itself, is record-setting.
"It's been an incredibly long, warm fall," said Bob Prescott, Director of Mass Audubon's Wellfleet Bay Wildlife Sanctuary, in early December. "We feel we're about a month behind."
In addition to the warmth, it hasn't been as windy as usual. That means that even if there are cold-stunned turtles out at sea, they're less likely to wash in.
Prescott says he sees the anomalies of this year and last as part of a long-term shift, and not necessarily a bad one. For one thing, the increase in strandings in New England is probably a reflection of increases in total population size, which is a sign of the success of conservation efforts.
But Prescott says there are other changes that suggest climate change is at play. New York Sound used to be the epicenter of fall strandings, and that has shifted to Cape Cod, suggesting that turtles are coming farther north than in the past. Prescott points to the fact that the Gulf of Maine is warming faster than ninety nine percent of the ocean.
There are also indications from the stomach content of stranded turtles that they may be taking a different route north, spending more time far offshore in the Sargasso Sea. Prescott says that could be related to shifts in the strength and location of the Gulf Stream that recent research has connected to Arctic warming.
Still, Prescott says two or three years isn't enough to know for sure whether this is the new normal. Research dollars are limited, and both sea turtle behavior and climate change are complicated topics. It could be some time before the full story becomes clear.