A fast-warming Gulf of Maine is rising faster than ever

Waves crash against the rocks at Portland Head Light, last fall in South Portland. Michael Dwyer/Associated Press, file

The fast-warming Gulf of Maine is rising faster than ever, with average monthly sea levels in Portland, Bar Harbor and Eastport breaking record after record over the last two years and driving storm surges and king-tide flooding higher and farther inland.

“The rate of sea level rise is increasing,” said Maine State Geologist Steve Dickson. “It’s no longer an inch per decade. It’s more. The tides now are about 7 to 8 inches above what they were when my grandfather was a kid playing on the shores of Jonesport.”

On Wednesday, during a Maine Climate Council briefing, Dickson said that future generations will be dealing with a few more feet, not inches. It was the third in a series of scientific updates in advance of the second edition of “Maine Won’t Wait,” the state’s climate action plan.

About 90% of global warming is occurring in the ocean, causing the water’s internal heat to increase, according to the U.S. National Aeronautics and Space Administration. Heat stored in the ocean causes the water to expand, which is responsible for one-third to one-half of global sea level rise.

The last 10 years were the ocean’s warmest decade since at least the 1800s, and 2023 was its warmest recorded year, according to NASA. In the Gulf of Maine, sea surface temperatures in 2021 and 2022 were the warmest on record. The Gulf of Maine was in a marine heat wave for 97% of 2022.

With an annual average of 52 degrees, the gulf is about 2 degrees hotter now than it was 30 years ago.

The higher temperatures, combined with shallow underwater topography that is not dissimilar to a kiddie pool sitting out in the sun, are driving sea level rise in the Gulf of Maine, said Nicole Price, a senior research scientist at the Bigelow Laboratory for Ocean Sciences in East Boothbay.

Since 1912, the Gulf of Maine has been rising about 0.8 inches per decade, according to sea level gauge readings. But since 2000, the rate of sea level rise has more than doubled, increasing to about 2 inches per decade, according to marine geologist Pete Slovinsky of the Maine Geological Survey.

The sea levels in Portland, Bar Harbor and Eastport have been especially high since 2023, Slovinsky said, roughly 2 to 3 inches above what they were in 2022. In 2023 and so far in 2024, Portland and Eastport broke half their monthly sea-level records and Bar Harbor broke almost two-thirds its records.

Another way to say it: Maine has logged more than a decade’s worth of sea level rise in only 16 months.

The Gulf of Maine isn’t alone, Slovinsky said. While the warming rate in the Gulf of Maine is much higher than the global average, the rising sea levels recorded here both over the last century and since the turn of the century mirror those recorded from North Carolina to Maine.

But the more than 50 scientists who have contributed to the forthcoming science and technical report to the Maine Climate Council – due out sometime this month – aren’t entirely sure what’s causing the rate of sea level rise to increase so dramatically since 2023, Slovinsky said.

In 2010, when the Gulf of Maine recorded its last sudden sea level rise, scientists noted the irregular fluctuation of atmospheric pressure over the North Atlantic Ocean and the slowing of the ocean currents that bring warm water north and cold water south, causing the seas to “slosh up” against the East Coast.

At this time, despite the unexpected spike in sea level rise since 2022, the contributing scientists are not calling for the Maine Climate Council to change its current sea level rise projections: 1.5 feet by 2050 and 4 feet by 2100. The council expects this much sea level rise in an intermediate-risk scenario.

The council advises coastal communities considering long-term infrastructure improvements like raising causeways or ferry landing repairs to plan for 3 feet of sea level rise by 2050 and almost 9 feet by 2100, even though they are likely 20 years ahead of even the highest-risk scenario projections.

EXTREME WEATHER ALSO A FACTOR

When questioned, however, Slovinsky acknowledged that sea level rise is just one driver of potentially damaging coastal flooding. Communities must also prepare for storm surges and wave damage as extreme weather increases in both frequency and ferocity due to climate change.

Shifting ocean circulation affects water temperatures, nutrients and the food web, even in the Gulf of Maine. Atmospheric carbon dioxide makes its way into the ocean, into the sea water, and makes it more acidic, with consequences for marine life.

For the first time, scientists advising the Maine Climate Council now have the data to make sea floor temperature projections as well as for sea surface temperatures, which is especially important given how much of Maine’s most valuable fisheries involve bottom-dwelling crustaceans.

According to the models, seabed water temperatures are expected to rise by almost 5 degrees by 2050, said Price, the Bigelow Laboratory researcher. Warming oceans will also create seasonal mismatches, leaving both larval lobsters and North Atlantic right whales unable to find the zooplankton they need to eat when and where it used to be.

Increasing acidification will also make it hard for Gulf of Maine shellfish to make their shells by 2050.

“Conditions are looking challenging,” Price said.

But it’s not all bad news, she said. New warmer water species are appearing in Gulf of Maine waters, like black sea bass, squid and Jonah crab, she said, and scientists are exploring ways to use the ocean to mitigate climate change, including using kelp and zooplankton to sequester heat-trapping carbon.