More than 200 sea turtles, stunned by the cold, wash off Cape Cod: NPR

The coasts of Cape Cod, Massachusetts, have seen an increase in the number of weakened and dead sea turtles, with more than 200 being washed in recent days.

Rescuers call this "cold stun" when tropical reptiles are trapped in cold water and because, they are ectothermic or depend on outside heat for their bodies to function, their systems are starting to stop.

Incapable of swimming, they can be pushed by the strong wind towards the shore or towards shallower waters, where they can literally die of cold.

"It was like they were frozen, fins in all odd positions as if they were swimming," said Robert Prescott, director of Wildlife Sanctuary at the Wellfleet Bay Wildlife Society of Massachusetts Audubon Society, Cape Cod Times.

Prescott told CNN that of the more than 200 turtles found off Cape Cod this week, 173 had died and 54 had survived. Many were Kemp turtles, sea turtles Kemp, the most endangered sea turtles in the world, said the sanctuary in a statement. Other species have also been discovered, including a logger nearly 300 pounds.

Jenette Kerr, spokesperson for the Wellfleet Bay Wildlife Refuge, told the Cape Cod Times that on Wednesday, 87 turtles were found, most of them alive. By the time of Thanksgiving, 82 people had been swept away by the sea, including one except one, which, according to Kerr, is due to "a dramatic change in the weather during the night."

In total, more than 400 turtles were discovered in the region this year. Some of this week's survivors were transported to the New England Aquarium Animal Care Center for rehabilitation.

Scientists say that turtles that migrate naturally move further north as climate change warms the planet's oceans. Some are now in Cape Cod Bay, where they are trapped "by the Cape's hook-shaped geography," the shrine announced.

Prevented from migrating to warmer waters, turtles remain vulnerable to unstable weather conditions, like the cold wave and gale winds this week.

"Sea turtles move further north along our shores … as the waters warm up and they expand their range," said biologist Wallace J. Nichols at NBC News. "When we get these fast swings of heat in temperature, turtles that have not arrived to the south definitely have problems."

"The beaching season" generally lasts between Thanksgiving and Christmas, said the sanctuary. This year's numbers have already exceeded what is typical for a year, said Prescott – and the total could reach 1,000 sea turtles by the end of December.

Over the last four decades, cold-stunned sea turtles have been on the rise, with more than 1,200 animals in 2014, according to the sanctuary.

"The reasons for the phenomenon are unclear, but much warmer waters in the Gulf of Maine and increased nesting productivity for some species of sea turtles could be two factors," the sanctuary said in its statement.