The Gulf of Maine, a semi-enclosed sea stretching from Cape Cod to Nova Scotia, is home to more than 3,000 species and supports some of the world’s most productive fisheries. This area is warming faster than 99% of the global ocean, an accelerated trend that has reversed a 900-year cooling period. This warming affects the health of its ecosystems and the communities that depend on them.
Causes of Rapid Warming in the Gulf
The rapid warming in the Gulf of Maine is driven by global and local factors. While rising atmospheric greenhouse gases warm all oceans, the Gulf’s specific oceanography amplifies this effect. Its C-shaped geography, enclosed by the underwater plateau of Georges Bank, traps water for long periods. This shape makes the shallow basin more susceptible to rapid temperature shifts.
A primary contributor to the accelerated warming is a change in major ocean currents. The balance between the cold Labrador Current from the Arctic and the warmer, northward-flowing Gulf Stream is being altered. As climate change causes Arctic ice to melt, the resulting influx of freshwater weakens the Labrador Current’s southward push. This allows the more powerful Gulf Stream to intrude further into the Gulf of Maine.
This dynamic is influenced by the weakening of the Atlantic Meridional Overturning Circulation (AMOC), a large system of ocean currents acting as a global heat conveyor. The slowing of the AMOC contributes to the northward shift of the Gulf Stream. The result is a greater volume of warm water entering the Gulf, an influx that has been particularly pronounced since a sudden increase in sea surface temperatures around 2010.
Impacts on Marine Ecosystems
Rising water temperatures are altering the marine ecosystems of the Gulf of Maine, with changes evident across the food web. A decline has been observed in the population of Calanus finmarchicus, a subarctic zooplankton that forms the base of the food web for many important species. This has cascading effects, impacting the health and distribution of animals that rely on it for food.
Commercial species are also experiencing shifts. Atlantic cod, adapted to cooler waters, have declined by more than 80% since the 1980s due to warming temperatures. American lobster populations initially saw faster growth, but now face increased shell disease and concerns about the long-term viability of southern populations. Projections suggest lobster abundance in the Gulf could decline significantly by 2050.
The warming is forcing a large-scale reorganization of species. Marine life is migrating to cooler, deeper waters or further north, including the endangered North Atlantic right whale, which has shifted its feeding grounds. At the same time, warmer-water species like black sea bass are becoming more common, introducing new predator-prey dynamics and altering the ecosystem.
Consequences for Regional Industries and Communities
The ecological shifts in the Gulf of Maine have direct consequences for the regional economy and coastal communities. The fishing industry faces significant challenges with the decline of some stocks and the uncertainty of others. This creates complex problems for fisheries management, as traditional boundaries and regulations become less effective when species migrate in response to changing temperatures.
Fishermen may need to travel further and into deeper waters to find their catch, increasing costs for fuel and gear. Beyond wild-capture fisheries, aquaculture operations face challenges from new diseases and the stress that warmer temperatures place on farmed species. The tourism industry, which relies on activities like whale watching and recreational fishing, is also vulnerable to these shifts in marine animal populations.
Scientific Monitoring and Future Projections
Scientists use a variety of tools to track the changes in the Gulf of Maine.
- A network of research buoys provides continuous data on water temperature and salinity at different depths.
- Satellite data is used to monitor sea surface temperatures.
- Information is collected from traditional ship-based surveys.
- Innovative programs like the Environmental Monitors on Lobster Traps (eMOLT) project use commercial fishing gear to collect real-time bottom temperature data.
This data informs climate models that project future conditions. Under a high carbon emissions scenario, models predict the average temperature in the Gulf could increase by 1.1°C to 2.4°C by mid-century, relative to the 1976–2005 average. This warming is expected to cause further declines in subarctic species and increases in temperate ones.
While long-term warming is the dominant trend, short-term variability exists. In late 2023 and into 2024, scientists noted a temporary influx of cooler, fresher water into the deep Gulf from the Labrador Current. This has led to predictions of a temporary pause in the rapid warming trend for the next several years, which could benefit cold-water species like cod. This highlights the need for continued monitoring to understand both long-term trends and short-term fluctuations.