Marine heatwaves lasting weeks to several months are exposing species and ecosystems to environmental conditions beyond their tolerance and acclimation limits . WGI AR6 concluded that marine heatwaves are more frequent , more intense and longer  since the 1980s, and since at least 2006 very likely attributable to anthropogenic climate change. Open-ocean, coastal and shelf-sea ecosystems, including coral reefs, rocky shores, kelp forests, seagrasses, mangroves, the Arctic Ocean and semi-enclosed seas, have recently undergone mass mortalities from marine heatwaves . Marine heatwaves, including well-documented events along the west coast of North America  and east coast of Australia , drive abrupt shifts in community composition that may persist for years , with associated biodiversity loss , collapse of regional fisheries and aquaculture  and reduced capacity of habitat-forming species to protect shorelines . 
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report