Marine Heatwaves Cause Massive Global Coral Bleaching

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Over 54% of reefs worldwide have bleached, with the percentage rising by the week. (Photo by Joan Li on Unsplash)

by | May 17, 2024

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The National Oceanic and Atmospheric Administration (NOAA) reports that the fourth global coral bleaching event on record is underway, with unprecedented marine heatwaves affecting the Atlantic, Pacific, and Indian Oceans. The NOAA Coral Reef Watch program’s heat-stress monitoring identifies high levels of marine heat stress that can cause extensive coral bleaching and mortality.

The bleaching event began in early 2023 and has already proved devastating to coral ecosystems in the Gulf of Mexico, Central America, the Red Sea, and the Persian Gulf, among other regions. These widespread bleaching events highlight the severity of shifting ocean circulation patterns, which could significantly affect global coral reef health.

Global Bleaching Impacts on Ocean Circulation

A close correlation between coral bleaching and changes in ocean circulation has been identified by NOAA researchers in a study using heatwave “hotspot analysis” to reveal accelerated heat transport from tropical to polar regions. These shifts in ocean circulation cause warming in sub-polar waters and accelerated polar ice melting, amplifying climate change effects that were not captured in previous projections.

As global warming accelerates, the slowing of ocean stratification and vertical mixing of surface and deep waters leads to increased heating of ocean currents, adding further stress to coral reefs that are already highly susceptible to temperature fluctuations. Thomas Goreau, the study’s lead author, expressed grave concern over these changes, highlighting how current projections overlook the feedback mechanisms affecting coral reefs.

Economic Consequences and Resilience-Based Management

Coral bleaching events are an ecological disaster, threatening the livelihoods and economies reliant on coral reef ecosystems. The NOAA Coral Reef Conservation Program (CRCP) actively incorporates resilience-based management practices and restoration strategies to protect these essential ecosystems. Efforts include deep-water coral nurseries, sunshade deployments, and advanced monitoring programs.

Through the Mission: Iconic Reefs program and the International Coral Reef Initiative’s Plan of Action, NOAA is working around the world to protect and restore coral ecosystems by fostering scientific research and sharing best practices, with collaboration across governments, industries, and local communities.

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