An intense heat wave at sea sets ocean temperature records in the North Atlantic

It’s not just country seeing record heat waves.

Ocean waters in the Northern Hemisphere have been unusually warm in recent weeks, with parts of the North Atlantic and North Pacific experiencing particularly intense marine heat waves.

Sea surface temperatures in these regions hit record levels this summer, said Dillon Amaya, a researcher with the National Oceanic and Atmospheric Administration’s Physical Sciences Laboratory in Boulder, Colorado. Parts of the Pacific and North Atlantic are sometimes anywhere from 2 degrees Celsius (3.6 degrees Fahrenheit) to 5 degrees C (9 degrees F) warmer than average, conditions that have not been observed since record keeping was about started six decades ago.

“It’s been very extreme — some of the hottest temperatures we’ve ever seen — and they’ve been hanging out for several months,” Amaya said.

Oceans naturally absorb and store heat, making these reservoirs good indicators of how much the planet is warming. Studies have shown that since 1970, oceans have absorbed more than 90% of the heat retained on Earth by greenhouse gas emissions.

As climate change accelerates the rate of ocean warming, scientists are concerned about the potential impacts on marine ecosystems, sea level rise and extreme weather.

NOAA’s annual “State of the Climate” report, released Aug. 31, found that ocean heat, measured from the surface to a depth of more than 6,000 feet, was the highest on record in 2021.

Increasing the base ocean temperature is worrisome, Amaya said, because it increases the likelihood of marine heat waves and persists for longer periods of time.

“Each marine heat wave will be warmer than the last because of the increase in greenhouse gases,” he said.

Researchers pay close attention to these temperatures because warmer oceans can intensify storms and increase the risks of extreme weather.

And globally, melting ice from warmer oceans could accelerate sea-level rise, posing a major threat to coastal communities and low-lying infrastructure. NOAA’s “State of the Climate” report found that global mean sea levels rose to new record highs for the 10th consecutive year in 2021.

But hotter-than-normal water also has an effect on the chemistry of the world’s oceans, absorbing carbon dioxide from the atmosphere, making ocean waters more acidic. This acidification, combined with sustained heat in certain bodies of water, can have a major impact on marine life, said Kathy Mills, a research scientist at the Gulf of Maine Research Institute, a nonprofit.

Marine heat waves, for example, could alter the migration patterns of certain marine animals, put new pressures on the region’s fish and invertebrates, or even allow invasive species to gain a foothold, she said. Part of her research includes studying the impact of warming oceans on marine ecosystems, and the resulting implications for local economies.

Mills and her colleagues have found that certain species, such as northern shrimp and cod, have struggled with the warmer conditions, while American lobster has fared better with the changing temperatures.

“We’re trying to understand how this will affect the biology of organisms, the population-level effects for species, and what these changes will mean for the fisheries in the region,” Mills said.

NOAA’s forecasts indicate that the current marine heatwaves in the northern Pacific and North Atlantic oceans could continue for several more months. Amaya said it is a worrying sign of what is to come if global warming continues unabated.

“There’s definitely something going on right now,” he said. “This tells me that there is something intractable in the climate system that is causing these heat waves at sea to last for a very long time.”