Hurricane Irma, a record Category 5 storm, is seen approaching Puerto Rico in this NOAA National Weather Service National Hurricane Center satellite image taken on September 6, 2017. Credit: NOAA | Reuters

Maine may not be as susceptible to tropical storms as Houston, Florida or the Caribbean, but warming ocean temperatures — similar to increases seen in this state — are making storms stronger and wetter, scientists say.

Warm ocean temperatures feed the power of storms, and as ocean temperatures along the eastern seaboard increase, they will sustain the power of storms for a longer duration as they travel north. Hurricanes, nor’easters and even thunderstorms will pack more of a punch as warm waters inch their way up the East Coast.

These are the ways that storms’ rising intensity could be felt in Maine, which sits on one of the planet’s most rapidly warming bodies of salt water.

Wind and rain

The most significant and widespread threat from a tropical storm or hurricane bearing down on Maine wouldn’t be the storm surge, according to John Jensenius, a meteorologist with the National Weather Service in Gray. It would be the fierce winds and heavy rains.

Intense storms would bring more rainfall in general, which in Maine has been blamed for declining salinity and higher levels of dissolved organic matter in the Gulf of Maine. As more fresh water overall runs into the gulf — despite occasional periods of drought — it suppresses the growth of phytoplankton, which are a key component of ocean life, functioning as an oxygen source and as a staple at the low end of the marine food chain.

Strong rains can have other effects, too. In 2012, after a particularly intense four-day deluge, an estimated population of 1,400 terns abandoned a nesting colony on Metinic Island off St. George.

A storm surge of a few feet would be minor compared to widespread flooding from overflowing lakes and rivers or damage from trees blowing over onto houses, into power lines and across roads, Jensenius said, adding that tornadoes often are a byproduct of cyclones making landfall.

Because cyclones rotate counterclockwise in the northern hemisphere, a storm that moves north tends to have higher wind speeds on its eastern side and more rain and flooding on its western side, Jensenius said.

The slower-moving the storm, the more rain falls on the landscape below, he said. And because Maine is largely a rural state, residents in more isolated areas could be stranded for days as they wait for floodwaters to recede or for emergency response crews to clear fallen trees from roadways.

More flooding

Interactive flood maps show that many places throughout the state can flood from prolonged torrential rain. But Maine’s long coastline also leaves some areas prone to storm surge. Rugged sections of shoreline with high bedrock likely would be well-protected but the state’s low-lying beaches and tidal estuaries, much of which are in southern Maine, could be inundated as storms push water ashore.
“When storm surges and/or extreme rain happen during higher tides, we experience flooding,” Gayle Bowness of Gulf of Maine Research Institute said. “As sea levels rise, the natural buffer of our tidal range decreases. Smaller storms are going to have larger impacts and the impacts of larger storms will be more intense.”

In downtown Bangor, for example, some of the low-lying areas around Kenduskeag Stream could flood as they did in February 1976, when water propelled by high tide and a storm with 100 mph wind gusts funneled into the bay and up the Penobscot River. In Portland, parts of which already are prone to flooding from heavy rains, much of the Bayside neighborhood could be underwater from a major storm surge.

Stronger nor’easters

Winter storms — often called “nor’easters” because of the dominant wind direction — also could become more intense as a result of warming oceans, Jensenius said.

Nor’easters occur when relatively warm air off the Atlantic runs into colder air blowing in from the north and west, creating a storm front that whips up winds and dumps large amount of rain or snow. As ocean temperatures rise, such storms are expected to bring more rain than snow, Jensenius said.

“If you have a warming climate, that would provide more moisture for storms,” he said. “A nor’easter needs that difference between cold air and warm air [to form].

More intense red tides

Bigger storms also could worsen seasonal outbreaks of red tide, scientists have said. Warming ocean temperatures by themselves aren’t expected to aggravate these seasonal blooms of the naturally occurring biotoxin, which can cause paralytic poisoning in people who eat shellfish with high concentrations of the harmful algae. But increasingly severe storms could lead to more intense blooms.

Red tides were aggravated by the storms that churned up the water column in the Gulf of Maine in 2003 and 2009. In 2003, it was Hurricane Juan that kicked up surf in the the gulf, while in 2009 it was Tropical Storm Danny.

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Bill Trotter

A news reporter in coastal Maine for more than 20 years, Bill Trotter writes about how the Atlantic Ocean and the state's iconic coastline help to shape the lives of coastal Maine residents and visitors....