In 2023, the global ocean heat wave was the biggest, the most intense, the most tenacious and the most sustained on record, new research reveals. Researchers suggest that these heat waves are driven by climate change and may indicate climate change points.
Global ocean heat waves (MHW) are long periods of unexpectedly warm ocean temperatures. These warm periods can critically threaten marine ecosystems by, for example, leading to coral bleaching and large amounts of marine die-off, and can pose economic challenges by disrupting fisheries and aquaculture. It is widely accepted that human-driven climate change is making MHW more destructive, but little is known about the ocean dynamics behind the phenomenon.
“Marine heat waves have emerged worldwide as one of the most serious threats to marine ecosystems,” Ryan Walter, a California Institute of Technology marine scientist who was not involved in the research, told Live Science.
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A climate change point?
In a study published Thursday (July 24th) in Journal Science, researchers used satellite observations and ocean circulation data to assess the 2023 MHW. They found that the year sets a new record of the temperature, duration and geographical range of MHW.
The most severe warming that occurred in the North Atlantic, Tropical, South Pacific and North Pacific accounted for 90% of unexpected marine heating in 2023. The North Atlantic MHW lasted for 525 days, while the Southwest Pacific MHW broke records of geographical degree and duration.
Related: 1 million seabirds have died due to hot blobs in the Pacific
Scientists have identified several drivers behind extreme MHW, including reduced cloud covering, weakened winds, and increased solar radiation due to changes in ocean currents.
They suggest that the 2023 MHW may indicate a fundamental change in marine dynamics. This could be an early warning of a climate change point. There is no singular definition of a turning point, but most researchers use it to mean a threshold where the specific effects of climate change are irreversible.
It is still unknown whether the ocean has yet to reach an important turning point. “It’s difficult to quantify the turning point,” Walter said. Because the ocean and atmosphere contain many feedback loops, it is difficult to accurately predict where the climate point will occur, as “changing one thing changes another.”
Other factors could also have an impact on the 2023 record-breaking ocean heat wave. A large-scale El Niño event – a climate cycle where waters off the Eastern Pacific Ocean are warmer than usual – that summer, “many heat is released into the atmosphere from deep oceans, and the author wrote Michael McFadden, a senior scientist at the atmosphere, creating an atmosphere that is not a senior scientist at the atmosphere. In the tropical Pacific, for example, a new paper was found to show that temperature abnormalities peaked at 34.9 degrees Fahrenheit (1.6 degrees Celsius) during the onset of El Niño.
McPhaden agreed that 2023 will be an astounding year for MHWS and other climate extremes, but said, “I don’t think 2023 is a turning point.” While extreme temperature events are increasing due to climate change, the natural fluctuations associated with El Niños also affect annual ocean measurements.
“There are years when things are off the charts and those will be the years when we have a big El Nino,” McFadden said.
Marine ecosystems and human livelihoods
Whether 2023 represents a turning point or not, extreme MHWs around the world highlighted the vulnerability of marine ecosystems and human life that rely on them. MHWS “not only impacts basic ecosystems such as kelp forests, sea grasses and coral reefs, but they all provide many valuable ecosystem services and support other species, as well as affecting many economies,” Walter said.
These extreme events can lead to the expansion of habitat for certain species. For example, the warm waters off the coast of California attracted venomous sea snakes at the equator to the state. “These ocean snakes, which normally live in the equatorial Pacific, can trace the warm waters of the north, even in parts of Central California,” Walter said.
These extreme MHWs are not the last. “What you’re looking at is the result of climate change,” McFadden said. “We just look at the extreme temperatures of the ocean and atmospheric air.”
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