Gulf of Maine

Rocky coastline on left, bright blue ocean on right.
Acadia is known for the rugged beauty of its coastline.

NPS Photo/Kristi Rugg

Acadia National Park protects over sixty miles of coastline and eighteen islands in the Gulf of Maine. The specific ocean conditions in the North Atlantic allow for the region’s diversity of marine life, including seabirds, marine mammals, tidepool organisms, and fish species that have long been the backbone of the local economy.

The Gulf of Maine is also one of the fastest-warming ocean regions, with average surface temperatures rising faster than 99% of marine waters around the world. As human activities continue to alter climate conditions, the shores of Acadia National Park will see significant changes.

Current Affairs

The Gulf of Maine is a semi-enclosed sea, bordered by the coastlines of Massachusetts, New Hampshire, Maine, New Brunswick, and Nova Scotia. Under the surface, the elevated sea floor of George’s Bank shapes the flow of currents and divides the Gulf of Maine from the Atlantic Ocean south of Cape Cod.

Two major currents, the Labrador Current and Gulf Stream, meet just outside this boundary. Within the Gulf of Maine, the coastline alters the course of cold water flowing into the Bay of Fundy, forming a gyre that deflects water southward.

As ocean water moves throughout the gulf, it transports heat, sediment, nutrients, and a variety of small organisms unable to swim against the current known as plankton. Currents carry the building blocks of the ecosystem on which all other marine life depends.

Shifting Conditions

“It is a curious situation that the sea, from which life first arose, should now be threatened by the activities of one form of that life. But the sea, though changed in a sinister way, will continue to exist; the threat is rather to life itself.” -Rachel Carson, The Sea Around Us

Anthropogenic, or human-caused, climate change is already altering conditions in the Gulf of Maine. Understanding changes in surface temperatures, sea level, currents, acidity, and salinity will help protect this unique place into the future.
Hand points at acorn barnacles attached to rock
Acorn barnacles depend on plankton as a food source.

NPS Photo


Melting Arctic sea ice is increasingly mixing with Gulf of Maine waters. In combination with changes in precipitation, this additional freshwater input to the gulf will change the salinity of the water. These changes will alter the structure of plankton communities, favoring certain species and leading to a cascade of effects throughout the marine food web.
Orange sea star underwater
Sea stars eat tide pool animals affected by ocean acidification.

NPS Photo

Ocean Acidification

Much of the carbon dioxide emitted through human activity has been absorbed by Earth’s oceans. This has changed the chemical composition of ocean waters around the world. As the ocean becomes more acidic, fewer carbonate ions are available for marine animals that develop calcium carbonate shells and skeletons. Many tide pool animals in Acadia form shells that help them survive in the rocky intertidal zone.
Male common eider stands on rocky shore
Common eiders breed on coastal islands. Males display a white, black, and green breeding plumage.

NPS Photo

Sea Level Rise

Warming water temperatures and melting ice are causing sea levels to rise on the coast of Maine and around the world. In the Gulf of Maine, shoreline habitats such as remote offshore islands, sand dunes, and rocky intertidal zones are important breeding grounds for shorebirds. Higher sea levels will also increase the impact of more severe storms and flooding, both tied to climate change, on coastal communities and parks. Different emissions scenarios cause projected sea level rise to range from 1 to 10 feet by 2100 (NOAA 2017), so actions taken today still have the power to change the future of Acadia’s coastline.
Sunset view of coastline and islands covered in snow
View of cold Gulf of Maine waters from Valley Peak in winter.

NPS Photo/Emma Lanning


The relationship between the Gulf of Maine’s strongest currents is changing. The cold water of the Labrador Current contains an increased amount of freshwater as a result of melting sea ice, and the warm Gulf Stream waters continue to shift north. The interplay between these two forces is the key to understanding climate change in the Gulf of Maine, as the ranges of marine species depend upon the existence of specific thermal habitats, or areas with a certain range of water temperatures.
Large waves along rocky coastline in winter
Climate change increases the frequency and intensity of hurricanes and winter storms.

NPS Photo/S. West


The sea surface temperature of the world’s oceans is increasing, and nowhere is this change more drastic than the Gulf of Maine. Since 2004, surface temperatures have risen 2-3 degrees Fahrenheit, making the Gulf of Maine one of the fastest-warming ocean regions. Increasing temperature is closely tied to other changing conditions and has far-reaching effects. Temperature increases lead to stronger storms and shifting ranges for marine life, including economically important animals like lobster, shrimp, scallops, and cod.

Sea Change

Visiting Acadia National Park is an opportunity to witness the effects of climate change firsthand. This is a place that has already begun to change as a result of human activity, yet also offers visitors a chance to reflect on how to protect it into the future. National parks are not just beautiful places to visit; the coastline protected by Acadia is a home for plants, wildlife, and coastal communities that depend on the Gulf of Maine. It also functions as a living laboratory, where researchers with the Schoodic Institute and Northeast Temperate Network work to expand existing knowledge of climate change and the global ocean.

Acadia National Park

Last updated: October 8, 2021