Last year, sea levels along the Boston coastline were, on average, higher than at any other point in recorded history: about 14 inches above levels in 1921, when records began.
“This hasn’t stopped or slowed down yet,” said Rob DeConto, a climate scientist who studies ice sheets in a warming climate and a professor at the University of Massachusetts Amherst.
The record-breaking sea level is yet another data point showcasing a decadeslong trend that is accelerating at a startling pace. As climate change worsens, the shoreline along much of the city will need new flood protections, such as berms, sea walls, and restored marshlands, as early as 2030, the latest available data provided by Boston plainly show.
As 2030 approaches, climate resilience experts told the Globe, the rapidly accelerating pace of sea level rise necessitates action. Bud Ris, a senior adviser for Boston’s Green Ribbon Commission who advised the city’s climate resilience plan, said Boston is “deep into overtime” on moving from conceptual flood protection plans to specific and concrete ones.
“It’s really important that we get a continuous line of defense along the waterfront and that all these properties are in sync,” Ris said.
The sea along Boston remains abnormally high. The tidal gauge on the Evelyn Moakley Bridge between downtown Boston and the Seaport in late January documented among the highest average monthly water levels recorded in the harbor, according to the National Oceanic and Atmospheric Administration. In February, the waterline hardly budged; data for March are not yet available.
Sea levels tend to fluctuate over months or years depending on factors including water temperature, wind strength, and lunar cycles. But over the long run, sea level rise in the modern era is primarily driven by climate change as glaciers and polar sea ice melt on a warming planet. The ocean has climbed a little more than a foot in Boston since 1921, but the average pace of sea level rise between 2001 and 2019 was about double that of the last century.
Now, as the waterline rises, high tides and bigger storms could bring flooding further inland.
In its strategy called “Climate Ready,” the city identified several low-lying areas that could be flooded during a severe storm with higher sea levels by 2030. For each potential “flood pathway,” the city analysis mapped general areas of the coast where new infrastructure could block the water.
East Boston is expected to be at a particularly high risk, as is the Wharf District in downtown Boston and parts of Dorchester.
“Our top focus is closing the 2030 flood paths in Boston,” Chris Osgood, senior adviser for infrastructure to Boston Mayor Michelle Wu, said in a statement. He noted Wu created a $75 million fund in the city’s budget that would leverage state and federal grants for coastal resilience projects.
“We are aggressively pursuing every state and federal grant we can, with new staff assisting in this effort,” Osgood said.
The city’s “Climate Ready” strategy was created more as a conceptual roadmap than an action plan. Many of the ideas in it, which range from elevated parks to sea walls to restored natural spaces, have yet to go through the sort of rigorous engineering and planning necessary to build them.
Some of the projects intended to block what the city calls “near-term” flooding, though, are already complete. For example, construction on McConnell Park in Dorchester included elevating portions of the site and a barrier wall made of granite blocks. And in the North End, the reconstruction of the Langone-Populo Park elevated the park by 7 feet and the Harborwalk by 4 feet, and bolstered an existing sea wall.
Other projects, according to Osgood, are “ramping up or underway,” including a city effort to coordinate flood defenses along Border Street in East Boston and a plan to elevate Ryan Playground in Charlestown.
Generally, the city envisions a response that resembles a long jigsaw puzzle: small and varied projects that lock together to form one continuous flood barrier. All together, the projects would cost several billion dollars, according to estimates by the city and climate experts.
About half of the coastline in Boston is owned by the state government, much of that land is leased to the private sector, with around one-third privately owned. While some commercial real estate developers have agreed to build flood protections as part of their massive coastal redevelopment projects, several of those have stalled in a shaky market for commercial real estate. The city owns about 16 percent of the Boston shoreline.
Osgood said Boston has sought to team up with other municipalities, the state, or private landowners to jumpstart flood protection projects. For example, Boston and Revere last year jointly received a $330,500 state grant to design a flood protection project on their border for the Belle Isle Marsh Reservation and Fredericks Park, with the goal of protecting Bennington Street, the MBTA Blue Line, community spaces, and private residences in the Beachmont neighborhood of Revere.
These measures could also help protect the residences being built at the nearby Suffolk Downs, where a massive complex is now underway. Yet, the two cities are seeking more funding to complete the design and permitting of the flood protections.
Toward the end of this decade, both climate change and natural patterns are expected to accelerate flood risks. A 19-year natural lunar cycle that extends the tidal range in Boston Harbor will begin late this decade, amplifying flood risks at the same time the rise in sea levels is expected to accelerate, DeConto said.
The pace of sea level rise in Boston, like much of New England, is outstripping the global average, in part because the land here is slowly sinking due to the effects of ancient glaciers and in part because the position of New England makes it more susceptible to sea level rise originating from melting glaciers in Antarctica.
Boston is likely to have a waterline 5 to 11 inches higher by the end of the decade than in 2000, regardless of what’s done to cut greenhouse gas emissions, and is likely locked into about 1 foot of sea level rise by the middle of the century, according to DeConto. And, there’s a chance it could be more.
But if any place in the country can figure out how to build the political and financial will to adapt to rising sea levels, Kathy Abbott, chief executive of Boston Harbor Now, said, it ought to be Boston. She said she’s encouraged by the leadership of Mayor Wu and Governor Maura Healey, both of whom have made responding to climate change priorities of their administrations.
“If we cannot figure out how to address this stuff in Massachusetts, then shame on us,” Abbott said. “I think things are lining up.”
Erin Douglas can be reached at erin.douglas@globe.com. Follow her @erinmdouglas23.