Scientists have discovered that intense heatwaves in the ocean can persist for longer periods in deeper water, posing a threat to sensitive marine species. This is particularly concerning as climate change is expected to increase the frequency of these extreme events. Since the industrial age, oceans have absorbed 90 percent of the excess heat resulting from carbon pollution caused by human activity.
These marine heatwaves, characterized by abnormally high water temperatures, have become more frequent and intense. They can have a devastating impact on species that are unable to migrate in order to escape the intolerably warm waters, such as corals in the Great Barrier Reef and kelp forests in southern Australia and the northeastern Pacific.
A recent study published in the journal Nature Climate Change examined the effects of temperature spikes in deeper waters, marking the first attempt to explore marine heatwaves below the surface. Lead author Eliza Fragkopoulou explained that previous studies on marine heatwaves have focused mostly on the ocean surface, and very little was known about their characteristics in the deep ocean.
Using on-site observations and modeling, researchers analyzed global marine heatwaves from 1993 to 2019, including data obtained up to a depth of 2,000 meters(6,562 feet) below the surface. They discovered that the intensity of heatwaves was highest at depths ranging from 50 to 200 meters below the surface, occasionally being up to 19 percent stronger than at the surface. The duration of these heatwaves also increased with depth, with warming persisting for up to two years after temperatures returned to normal on the surface.
To assess the vulnerability of marine creatures to thermal stress, researchers examined a proxy measure known as cumulative intensity and mapped it against the distribution of biodiversity at the edge of their maximum heat tolerance. They found that up to 22 percent of the global oceans experienced high stress conditions. Due to regional variability, measuring biodiversity exposure to marine heatwaves is a complex task, and the duration of these events varied by location due to different oceanic conditions.
Fragkopoulou, a researcher at Portugal’s University of Algarve, suggested that the impact on biodiversity is likely greatest from the surface to a depth of 250 meters. The regions categorized as highly exposed were found to be predominantly in the North Atlantic and Indian Oceans, at depths between 1,000 and 2,000 meters.
Another study published in Nature last month indicated that some marine creatures are more resilient to heatwaves than others. This finding suggested that ocean fish can endure marine heatwaves without experiencing a significant impact on their populations. Fragkopoulou emphasized the need for further research on heatwaves in the deeper oceans to understand their potential impacts on tourism and fisheries. She stressed the urgency of more comprehensive monitoring efforts in order to grasp the effects of marine heatwaves on deep-sea biodiversity.
In conclusion, marine heatwaves are becoming more frequent and intense, with deeper waters experiencing longer-lasting heatwaves. This poses a threat to marine species, especially those unable to escape these high temperatures. The study highlights the need for better monitoring of the deeper oceans to understand the impacts on biodiversity, tourism, and fisheries.
Keywords: heatwaves, deep ocean, marine species, climate change, extreme events, abnormally high water temperatures, carbon pollution, global warming, coral reefs, kelp forests, Nature Climate Change, thermal stress, biodiversity, vulnerability, North Atlantic, Indian Ocean, tourism, fisheries.