The tufted puffins started washing ashore on St. Paul Island in mid-October—first a handful, then dozens, then so many that volunteers patrolling to collect dead birds began walking their four-wheelers rather than riding. It was easier than getting off every few feet.

The hundreds of dead, emaciated puffins showing up on this isolated, wind-swept scratch of land in the Pribilof Islands in the middle of the North Pacific suddenly has scientists worried—about the population of this white-masked, orange-beaked seabird, but also about what their deaths may portend for the normally productive Bering Sea.

A stretch of water that provides more seafood than any other in North America saw such record-warm temperatures earlier this year that scientists suspect the ocean food web there has shifted. That could spell big downturns for marine life, from seabirds and fur seals to salmon, crab and the $1 billion-a-year pollock fishing industry that provides flaky white filets for everything from McDonald's fish sandwiches to frozen fish sticks.

"The Bering Sea has been off-the-charts warm," said Nate Mantua, an ecologist at NOAA’s Southwest Fisheries Science Center in Santa Cruz, California. "We've never seen anything like this. We're in uncharted territory. We're in the midst of an extraordinary time."

In the last few years another patch of unusually warm water that settled into the Gulf of Alaska and merged with warm waters in southern California completely transformed the coastal ocean. For months, scientists off Oregon found almost none of the fatty-rich copepods that form the base of the food web. Sea lions, common murres, and Cassin's auklets died by the thousands because of a lack of food. Scores of whales and sea otters turned up dead in Alaska. The West Coast saw it's most toxic and longest-lasting harmful algal bloom ever. (Read more about this warm water blob.)

Master Predators of the Sea

But the subarctic waters of the Bering Sea, coming off a strong period of cold water and record sea-ice in 2012 and 2013, seemed mostly spared. Waters were unusually warm beginning in 2014, but not ridiculously so. Last year would have seen more normal ice, if warm water from the Gulf of Alaska hadn't poured into the Bering Sea through the Aleutian Island chain and kept the ice at bay.

But all that changed this year. Even the pool of cold water that normally rests on the bottom of the Bering Sea was at times 6 degrees Celsius warmer than usual.

"The maximum summer temperatures in the Bering Sea were the warmest we've ever seen," said Phyllis Stabeno, with NOAA's Pacific Marine Environmental Lab. "And the minimum temperature—the coldest it gets in winter—was warmer than several of the last years."

Under normal cycles in the Pacific Ocean, warm water usually translates to less food, and so far that's what scientists are seeing, especially among the tiny copepods that are food for smaller fish and other animals. But it's actually worse than normal.

"When it's warm we usually no longer have a lot of large, fatty zooplankton around," Stabeno said. Instead, the sea usually includes smaller, less nutritious zooplankton. "But this year there just wasn't much of anything."

Said Janet Duffy-Anderson of the Alaska Fisheries Science Center, "That bodes poorly for fish and birds and mammals. It's that zooplankton prey base that provides food for young pollock that are then eaten by birds and cod and halibut and even older pollock."

That appears to be what has happened with puffins in the remote Pribolofs.

View Images Scientists suspect the puffins are starving to death as an exceptional warm Bering Sea alters the food web, making the fish these deep-diving seabirds rely on scarce. Photograph by Paul Melovidov

Mass Deaths

In early October, Lauren Divine, co-director of the ecosystem conservation office for St. Paul's Aleut community, was given two dead puffins to take back to Anchorage for research. At the time she though little of it. On this 40-square-mile island, of roughly 500 people, dead birds wash up once in awhile.

But within a few days it was obvious something was wrong.

"On the 17th we started doing surveys of the two main beaches and we came up with about 40 birds that first day," said volunteer Aaron Lestenkof. "Since then it's been about 20 to 30 birds each time we go out."

Several hundred birds have now washed up, nearly 200 times the normal rate. And since St. Paul and its rocky sister island, St. George, are the only land masses anywhere nearby, scientists are certain they're seeing just a tiny fraction of the deaths.

"In 10 years of monitoring, we've only seen six puffins wash in—total," said Julia Parrish, a University of Washington professor who coordinates a West Coast volunteer bird-monitoring network. "Now we've seen nearly 250 in 20 days. And these islands are small dots in the middle of a huge ocean. The entire puffin population is only 6,000 birds, and we project half that many may be affected."

Parrish said the birds—deep-diving fish eaters that chow on forage fish, such as baby walleye pollock—aren't sick. Scientists see no evidence of disease. The animals are just in such an advanced state of starvation "they appear to be eating themselves inside out." Even if she wasn't already aware of the last two years of bird die-off events along the West Coast and Alaska, she said, this is unusual enough to be worrisome.

Puffins have seen trouble before. One year after the unusually warm 2012, Atlantic puffins in the Gulf of Maine suffered their worst reproductive season ever—until this year. Breeding of puffins in Iceland has been collapsing for a decade. But along the Pacific adults are simply washing up dead.

"Clearly something very weird is going on," Parrish said. "It's basically every year now we're getting some huge mass-mortality event. It seems that the bottom-up changes provoked by the atmosphere are creating massive, massive changes in marine ecosystems. And the forage fish that everything depends on are taking it in the shorts."

What does that mean for the rest of the creatures in the ocean?

"We don't know," Parrish said. "The Bering Sea is an incredibly big place, and we're just seeing this now." (Learn how puffins are tougher than they look.)

Iceland Puffin Threatened December 5, 2008—In Iceland's remote Westman Islands, warming weather is threatening a beloved mascot: the Atlantic puffin.





What’s Causing the Warmth?

Mantua said the strange behavior in the atmosphere that helped the Gulf of Alaska's warm "blob" form in 2013 shifted again late this spring, with a high-pressure system setting up over the entire North Pacific. That led to an extended warm period across Alaska from May through September.

Then, in October, the patterns changed again, with significant storms in the Gulf of Alaska. But in the Bering Sea wind brought warm air and water from out of the south.

"These patterns in the atmosphere are big," he said. "They span much of the North Pacific and can create warm or cold patches at the same time. But it's the fact that there has been so much persistence in these patterns that has led to such extraordinary ocean temperatures. That, to me, is the big mystery. We just keep going from one extreme to another. If you get 10 or 12 days that are stuck in the same pattern, then the ocean is going to slowly build up heat."

Scientists are still grappling with trying to determine how much of this change is likely linked to climate change. Some have argued that melting sea ice has affected the jet stream, causing it to be more wobbly. Others have suggested these strange anomalies are connected to warmth in the tropics but are largely just extreme versions of normal climate fluctuations.

Regardless, for now, marine scientists are planning to spend extra time at sea, trying to assess what all this means for the North Pacific—particularly for Alaska's fishing industry, which supplies half the nation's catch of seafood.