This one picture sums up climate change's growing role in coastal flooding

This one picture sums up climate change's growing role in coastal flooding
Boston Harbor flooding during a major nor'easter on March 2, 2018. (Look at the sign.)Boston Harbor flooding during a major nor’easter on March 2, 2018. (Look at the sign.)

Image: Twitter/Matt Beaton

Boston is bearing the brunt of its second major nor’easter in two months, and it’s a beast of a storm. 

The city experienced its third-highest storm tide on record on Friday morning at 14.67 feet. On Friday night, it’s likely to come close to, tie, or more likely, eclipse it’s all-time highest storm tide set during the “Bomb Cyclone” on Jan. 4.  The record tide will be caused by a combination of about 5 feet of storm surge, astronomical high tides, high waves, and long-term sea level rise. 

The storm, which underwent an unusually rapid period of intensification known as bombogenesis on Friday, meaning that its minimum central air pressure plummeted by at least 24 millibars in 24 hours, is extreme even by the standards of New England’s long history of powerful winter storms known as nor’easters. 

Satellite image showing the March 2 nor'easter, with an arrow showing the long easterly fetch.

Satellite image showing the March 2 nor’easter, with an arrow showing the long easterly fetch.

Image: CIRA/RAMMB

Winds, for example, reached 90 miles per hour on Cape Cod on Friday, while coastal communities prone to flooding, like Scituate, Massachusetts, and Quincy, saw some of their worst inundation on record. The storm has what meteorologists call an unusually long “fetch,” meaning that its winds are blowing in one direction across a long distance. This sets a lot of water in motion, moving toward the coast of southern New England. It’s driving North Atlantic waters from east to west, toward eastern Massachusetts, across hundreds of miles of ocean, which is accentuating the flood threat. 

Hidden amid all these factors, and often overlooked, is one that is a growing threat to Boston, and for that matter, coastal regions around the world: sea level rise.

The photograph of the climate change education sign being inundated in Boston Harbor on Friday was taken by Matt Beaton, who serves as Massachusetts’ secretary of the Executive Office of Energy and Environmental Affairs under Gov. Charlie Baker. In a Twitter message, he said that this storm and the “Bomb Cyclone” show the risks the state is facing. 

“I think it highlights our most obvious vulnerabilities to climate change,” Beaton said in a Twitter message. “The frequency and intensity of these events are alarming and I think we are experiencing things we are likely to see more often in the future,” he said. 

According to Beaton, who posted the image to his personal Twitter account, Massachusetts is developing a “comprehensive adaptation plan” to cope with sea level rise-related impacts, among others.  

Projected map of flooding in Boston from a 1 percent chance flood at high tide in the 2050s, given sea level rise. Blue areas represent inundated locations.

Projected map of flooding in Boston from a 1 percent chance flood at high tide in the 2050s, given sea level rise. Blue areas represent inundated locations.

Image: Climate ready boston. 

In the Boston area, sea levels rose about 9 inches in the 20th century, according to a 2016 report by the city, called Climate Ready Boston. In New York City, sea level had risen by nearly a foot between 1900 and when Hurricane Sandy struck in 2012, putting more of the city at risk of flooding.

The city of Boston’s report projects another 8 inches of sea level rise relative to land by 2030, and as much as 1.5 feet above 2000 levels by the year 2050. Subsequent studies have raised sea level rise projections due to more pessimistic projections of melting from land-based ice sheets.

What this means is that future nor’easters will be providing storm surges and high tides with a higher starting point, making it far easier for records to be broken, and putting areas now considered to be outside of coastal flooding risk zones in peril.

Sea level rise, caused mainly by heating-related expansion of the oceans and melting land-based ice, didn’t create the towering waves pounding the Massachusetts coastline on Friday into Saturday. However, it’s putting coastal areas at greater risk with each subsequent storm.

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