Ocean warming is putting coastal economies in hot water

Ocean-related tourism and recreation supports more than 320,000 jobs and $13.5 billion in goods and services in Florida. But a swim in the ocean became much less appealing in the summer of 2023, when water temperatures in Miami reached as high as 101 degrees Fahrenheit (37.8 Celsius).

The future of some jobs and businesses across the ocean economy has also become less certain as the ocean warms and damage from storms, rising sea levels and increased marine heat waves.

Ocean temperatures have risen over the past century and reached record levels for much of last year, driven largely by increased greenhouse gas emissions from burning fossil fuels. Scientists estimate that more than 90% of the excess heat produced by human activities is taken up by the ocean.

This warming, hidden for years in data of interest only to oceanographers, is now having profound consequences for coastal economies around the world.

Understanding the ocean’s role in the economy is something I’ve been working on for more than 40 years, currently at the Middlebury Institute of International Studies’ Center for the Blue Economy. Primarily, I study the positive contributions of the ocean, but this is beginning to change, sometimes dramatically. Climate change has made the ocean a threat to the economy in many ways.

Risks of sea level rise

One of the biggest threats to economies from warming oceans is sea level rise. As water heats up, it expands. Along with meltwater from glaciers and ice sheets, the thermal expansion of water has increased flooding in low-lying coastal areas and put the future of island nations at risk.

In the US, rising sea levels will soon overwhelm Isle de Jean Charles in Louisiana and Tangier Island in the Chesapeake Bay.

Flooding at high tide, even on sunny days, is becoming more common in places such as Miami Beach; Annapolis, Maryland; Norfolk, Virginia; and San Francisco. High tide flooding has more than doubled since 2000 and is on track to triple by 2050 along the nation’s coasts.

Sea-level rise also pushes saltwater into freshwater aquifers, from which water is extracted to support agriculture. The strawberry crop in coastal California is already being affected.

These effects are still small and very localized. Much greater effects come with increased storms from sea level.

Rising sea levels could exacerbate storm damage

Warmer ocean water fuels tropical storms. It’s one reason forecasters are warning of a busy 2024 hurricane season.

Tropical storms pick up moisture over warm water and transfer it to cooler areas. The warmer the water, the faster the storm can form, the faster it can intensify and the longer it can last, resulting in destructive storm surges and heavy downpours that can flood cities far from the coast.

When these storms come on top of already higher sea levels, the waves and storm surges can dramatically increase coastal flooding.

Tropical cyclones caused more than $1.3 trillion in damage in the US from 1980 to 2023, with an average cost of $22.8 billion per storm. Most of this cost is absorbed by federal taxpayers.

It’s not just tropical storms. Maine saw what can happen when a winter storm in January 2024 generated tides 5 feet above normal that flooded coastal roads with seawater.

What does this mean for the economy?

The potential future economic damage from sea level rise is unknown because the rate and extent of sea level rise is unknown.

One estimate puts the costs from sea-level rise and storm surge alone at over $990 billion this century, with adaptation measures likely to reduce this by just $100 billion. These estimates include direct property damage and damage to infrastructure such as transportation, water systems, and ports. Impacts on agriculture from saltwater intrusion into aquifers that support agriculture are not included.

Marine heat waves leave fishing in trouble

Rising ocean temperatures are also affecting marine life through extreme events, known as marine heat waves, and more gradual long-term temperature changes.

In the spring of 2024, a third of the global ocean was experiencing heat waves. Corals are facing their fourth global bleaching event on record as warmer ocean temperatures cause them to expel the algae that live on their shells and give the coral color and provide food. While corals sometimes recover from bleaching, about half of the world’s coral reefs have died since 1950, and their future beyond the middle of this century is bleak.

The loss of coral reefs is more than their beauty. Coral reefs serve as nurseries and food bases for thousands of species of fish. NOAA estimates that about half of all federally managed fisheries, including snapper and grouper, rely on reefs at some point in their life cycle.

Warmer waters cause fish to migrate to cooler areas. This is particularly evident with cold-water-loving species, such as lobsters, which have steadily migrated north to escape warming seas. The once-powerful lobster fishery in southern New England has declined sharply.

In the Gulf of Alaska, rising temperatures nearly wiped out snow crabs, and a $270 million fishery had to shut down completely for two years. A major heat wave off the Pacific coast lasted several years in the 2010s and disrupted fishing from Alaska to Oregon.

This is not coming back anytime soon

Accumulated ocean heat and greenhouse gases in the atmosphere will continue to affect ocean temperatures for centuries, even if countries reduce their greenhouse gas emissions to net zero by 2050 as hoped. So while ocean temperatures fluctuate from year to year, the overall trend is likely to continue rising for at least a century.

There’s no cold water faucet we can just turn on to quickly return ocean temperatures to “normal,” so communities will have to adapt as the entire planet works to slow greenhouse gas emissions to protect ocean economies for the future.