At the bottom of the ocean, they discover heat waves that threaten fisheries and ecosystems.

In an article published in the journal Nature CommunicationA team led by NOAA researchers used a combination of observations and computer modeling to create the first comprehensive assessment of marine heat waves at the bottom of the fertile waters of the continental shelf surrounding North America.

“Researchers have been investigating marine heatwaves at the seafloor for more than a decade,” said Dillon Amaya, lead author of NOAA. “However This is the first time we’ve been able to dive that deep. and evaluate how these extreme events developed on the shallow seabed.”

Marine heat waves significantly affect the health of ocean ecosystems around the world. It disrupts the productivity and distribution of organisms as small as plankton and as large as whales. Therefore, scientists try to study, monitor and predict the timing, intensity, duration and physical factors of these events.

Much of this research has focused on extreme ocean surface temperatures, with much higher quality observations taken by satellites, ships and buoys. Sea surface temperatures can also be indicative of many physical and biochemical properties of the oceans of sensitive marine ecosystems, making analysis easier.

Marine heatwaves have increased 50% in the last decade

About 90% of the excess heat from global warming has been absorbed by the ocean.It has warmed by about 1.5 °C in the last century. Marine heat waves have become 50% more frequent in the last decade.

In recent years, scientists have intensified their efforts to investigate marine heatwaves throughout the entire water column using the limited data available. However previous research did not take into account the extreme temperatures on the ocean floor along the continental shelves.It provides critical habitat for important commercial species such as lobster, scallops, crab, flounder, cod and other ground fish.

Due to the relative scarcity of bottom water temperature datasets, the scientists used a data product called ‘reanalysis’ to make their assessment; this started with existing observations and used computer models to simulate ocean currents and the effect of the atmosphere to “fill in”. gaps.” Using a similar technique, NOAA scientists have been able to reconstruct the global climate since the early 19th century.

Ocean reanalyses have been around for a long time, but only recently have they become sufficiently accurate and high-resolution enough to study ocean features, including near-shore bottom temperatures.

Research team from NOAA, CIRES and NCAR, On the continental shelves around North America, deep-sea heat waves tend to persist longer than their surface counterparts. and may have greater warming signals than the surface waters above it.

Deep sea and surface sea heat waves can occur simultaneously in the same place, especially in shallower areas where surface and bottom waters mix.

But seafloor heatwaves can also occur with little or no evidence of surface warming, with important implications for the management of commercially important fisheries. “This means It can happen without managers realizing it, until the effects begin to be felt.Amaya has been warned.

Serious economic and ecological consequences

In 2015, a combination of harmful algal blooms and kelp forest habitat loss off the West Coast of the United States, both caused by The Blob, Causing the closure of seafood restaurants that cost the economy more than $185 million, According to 2021 research.

Commercial Dungeness crab fishing in three states recorded a loss of $97.5 million. Coastal communities in Washington and California lost a total of $84 million in tourism spending due to recreational closures.

A groundfish survey published by NOAA Fisheries in 2021, The Gulf of Alaska cod dived during The Blob episode and experienced a 71% drop in abundance between 2015 and 2017. Instead, juvenile ground fish and other marine life in the Northern California Current thrived in these unprecedented ocean conditions, according to a 2019 paper by Oregon State University and NOAA Fisheries researchers.

Unusually hot bottom water temperatures it has also been linked to the spread of invasive lionfish in the southeastern United States, bleaching of corals and subsequent declines in reef fish, changes in survival rates of juvenile cod in the Atlantic, and disappearances of lobster populations. Near the coast in southern New England.

The authors say it will be important to maintain existing continental shelf monitoring systems and develop new real-time monitoring capabilities to alert marine resource managers to bottom warming conditions.

“We know that Early detection of marine heatwaves is essential for proactive management of ocean costRo,” said oceanographer Michael Jacox. “It is now clear that we need to pay more attention to the ocean floor, where some of the most valuable species live and can experience heat waves very different from those on the surface. ” added.

Reference work: https://www.nature.com/articles/s41467-023-36567-0

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