The Gulf of Maine is warming faster than 99% of the world’s marine waters

Few stretches of ocean are changing as fast as the one off Acadia National Park. The Gulf of Maine is one of the fastest-warming ocean regions, with average surface temperatures rising faster than 99% of marine waters around the world. The park protects over sixty miles of coastline and eighteen islands along it, so what happens in the gulf happens on Acadia's shores.

Acadia is known for the rugged beauty of its coastline. NPS photo by Kristi Rugg.

A sea shaped by currents

The Gulf of Maine is a semi-enclosed sea bordered by the coasts of Massachusetts, New Hampshire, Maine, New Brunswick and Nova Scotia. Below the surface, the raised sea floor of George's Bank shapes the flow of water and divides the gulf from the Atlantic Ocean south of Cape Cod.

Two major currents, the Labrador Current and the Gulf Stream, meet just outside that boundary. Inside the gulf, the coastline changes the course of cold water flowing into the Bay of Fundy and forms a gyre that pushes water southward.

Moving water carries heat, sediment, nutrients and plankton, the small organisms that cannot swim against a current. The park describes these currents as carrying the building blocks of the ecosystem that all other marine life depends on. The specific ocean conditions of the North Atlantic support seabirds, marine mammals, tidepool organisms and fish that have long been the backbone of the local economy.

What human-caused climate change is altering

The park names five conditions to watch: salinity, acidity, sea level, currents and temperature.

Acorn barnacles depend on plankton as a food source. NPS photo.

Salinity. Melting Arctic sea ice is increasingly mixing with gulf waters, and with changes in precipitation the extra fresh water will change how salty the water is. That will alter plankton communities, favoring certain species and setting off a cascade of effects through the marine food web.

Sea stars eat tide pool animals affected by ocean acidification. NPS photo.

Acidification. The oceans have absorbed much of the carbon dioxide people emit, which changes the chemistry of the water. As the ocean grows more acidic, fewer carbonate ions are available to animals that build calcium carbonate shells and skeletons, and many tide pool animals in Acadia form shells that help them survive in the rocky intertidal zone.

Common eiders breed on coastal islands. Males display white, black and green breeding plumage. NPS photo.

Sea level. Warming water and melting ice are raising sea level on the Maine coast and worldwide. Offshore islands, sand dunes and rocky intertidal zones are important breeding grounds for shorebirds. Higher seas will also add to the effect of more severe storms and flooding on coastal communities and parks. Depending on emissions, projected sea level rise ranges from 1 to 10 feet by 2100 (NOAA 2017), so actions taken today can still change Acadia's coastline.

View of cold Gulf of Maine waters from Valley Peak in winter. NPS photo by Emma Lanning.

Currents. The relationship between the gulf's strongest currents is shifting. The cold Labrador Current carries more fresh water because of melting sea ice, while warm Gulf Stream water keeps moving north. The park calls the interplay between the two the key to understanding climate change in the gulf, because marine species' ranges depend on specific thermal habitats, areas with a certain range of water temperatures.

Climate change increases the frequency and intensity of hurricanes and winter storms. NPS photo by S. West.

Temperature. Since 2004, surface temperatures in the gulf have risen 2-3 degrees Fahrenheit. Warmer water is tied to stronger storms and to shifting ranges for marine life, including economically important animals such as lobster, shrimp, scallops and cod.

Why Acadia matters here

The park presents itself as a place to see climate change firsthand and to think about how to protect the coast. It also works as a living laboratory: researchers with the Schoodic Institute and the Northeast Temperate Network work there to expand what is known about climate change and the global ocean.

Sources

• National Park Service, Acadia National Park, Gulf of Maine; rewritten in hubnx's own words. The Rachel Carson quotation in the original is left out.