A foggy morning on Vinalhaven’s Carvers Harbor last July. Brianna Soukup/Staff Photographer

Last year was the warmest on record for the Gulf of Maine, with average sea surface temperatures shattering the previous high mark set during a massive “ocean heat wave” in 2012 that triggered green crab invasions, the starvation of puffin chicks and an early lobster shed.

Surface temperatures in 2021 ran a staggering 4.2 degrees Fahrenheit above normal, the highest deviation in the 40 years that satellite records of sea surface temperatures have been collected in the gulf, according to a new report released Monday by scientists at the Gulf of Maine Research Institute in Portland. By comparison, the “Great Ocean Heatwave” year of 2012 had an anomaly of 3.7 degrees.

“This is pretty significant in a climatological sense, but it’s likely to be one of the coolest years we’ll experience for the indefinite future,” said co-author David Reidmiller, director of GMRI’s Climate Research Center. “We are almost certain not to go to zero (greenhouse gas) emissions overnight or next year or in the next decade, so we will see this warming trend continue.”

Over the past 18 years the Gulf of Maine has been one of the most rapidly warming parts of the world ocean, a threat to a body of water that’s home to many cold water species already living at the southerly edge of their range. The changing climate regime – driven by changes in the jet stream and the course and speed of the Gulf Stream and Labrador Current fostered by the rapid meltdown of the Arctic and Greenland ice sheets – has been implicated in shifts in lobster abundance, endangered North Atlantic right whale feeding grounds, and the food puffin chicks, herring and other species rely on.

“Even though breaking temperature records is almost becoming the norm now, there will be more surprises in store and staying tuned to what is going on in the gulf is very important,” said Nick Record, a biological oceanographer at the Bigelow Laboratory for Ocean Sciences in Boothbay, who was not involved in the report. “So much of what we are seeing change in the Gulf of Maine is tied directly to temperature, so it’s probably the most important variable to be keeping track of.”

Puffins are regarded as one of the canaries in the coal mine for warming effects, and they had a tough year in 2021, presumably because the warm temperatures are reducing populations of the tiny fish the birds feed their chicks. At the gulf’s largest puffin colony on Machias Seal Island – a disputed border territory occupied by Canada – scientists recorded the worst survival results ever. On average, 75 percent of hatchlings survive to fly away at the end of each season, but last year the figure was just 6 percent.

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“Growth rates were very slow and it seemed the adults were unable to find food to feed their chicks,” said Heather Major, associate professor of biology at the University of New Brunswick, who heads monitoring efforts on the island. “Even those puffins that survived to 35 days – when they are considered old enough to successfully fledge – were very small and mostly covered in down. We expect these fledgers would not have survived once they departed the island.”

Sea surface temperatures around the island, Major said, were higher than normal throughout the birds’ reproductive season.

The situation wasn’t much better at Maine’s other islands. At Petit Manan off Jonesport only 10 percent of puffin pairs were able to successfully raise a chick, and at Matinicus Rock the figure was 34 percent.

“We saw puffins and terns feeding their chicks more warm water adapted fish, such as butterfish and rough scad,” that don’t have as much nutritional value, recalled Don Lyons, director of the National Audubon Society’s seabird institute, which watches over the colonies on several midcoast islands. “Puffins at Eastern Egg Rock even appeared to be scavenging cut-up fish – perhaps bait discarded by fishers – which was a new observation.” Unusually heavy rainstorms – another predicted effect of global warming in Maine – flooded nests, causing many wet chicks to die of exposure.

“Even the chicks that survived to leave the islands were often very skinny and small for their age,” he noted. “Our island technicians took to calling some of the young puffins ‘micropuffins.’”

A puffin on Eastern Egg Rock, home to the world’s first restored Atlantic Puffin colony. At the gulf’s largest puffin colony on Machias Seal Island – a disputed border territory occupied by Canada – scientists recorded the worst survival results ever. Derek Davis/Staff Photographer

GMRI’s Kathy Mills, a co-author of the warming report, said they’ve continued to see warmer water species like longfin squid and black sea bass intruding into the Gulf of Maine, but it no longer shocks people. “Those changes might have been really eye-catching in 2012 and they are still happening now, but we are perhaps getting more familiar with them,” Mills said.

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That said, some of the most destructive developments seen as a result of the 2012 heat wave did not come to pass in 2021, including an explosion of destructive green crabs that devour mussels and destroy eel grass meadows and lobsters shedding early, which can throw a wrench into the seasonal expectations of lobster processors and markets. The early lobster shed in 2012 led to violent confrontations between Canadian fishermen and truck drivers bringing Maine lobsters to glutted New Brunswick processing plants.

Scientists said the key reason those immediate effects haven’t been seen this time is thought to be that the worst warming anomalies in 2012 occurred in the spring, which sets the tone for many species, whereas they happened in the late summer and fall last year.

GMRI reported the average sea surface temperature in the gulf in 2021 was 54.1 degrees, a half degree higher than 2012 and 4.2 degrees higher than the average for the “normal” period between 1982 and 2011, before ocean heat waves became commonplace.

The five warmest years for the gulf have all occurred since then, with 2016, 2020 and 2018 occupying the third-, fourth- and fifth-place slots.

The longer-term warming trend has been linked to other ecological shifts, including the more frequent sightings of warmer water species such as the ocean sunfish.

October 2021 was especially remarkable in that every single day set an all-time daily record for average sea surface temperatures in the gulf. For the year overall, scientists found record daily highs on 46 percent of days – 169 daily records in all.

“The good news is that the future is still in our hands,” GMRI’s Reidmiller said. “If we are able to reduce greenhouse gas emissions at a global scale, we will certainly be able to limit the changes we see in the future.”

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