Marine heatwaves are periods of discrete anomalously high  sea surface temperatures that persist for a minimum 5 d but up to several months . There have been MHWs attributed to climate change in every marine system of North America including large areas of the Northwest Atlantic , Caribbean Sea , Bering Sea  and central through Northeast Pacific  . Such MHW events have affected kelp forests , corals , seagrasses, bottom-dwelling organisms, marine birds , mammals , fish and shellfish, and marine-dependent human communities . Increased sea temperatures directly increase metabolic demand and change productivity and behaviour of fish species  as well as induce rapid redistribution of species poleward and to deeper, colder waters . In the Pacific, from the Baja Peninsula to the Bering Sea, there is evidence of widespread shifts in coastal biota and multi-trophic-level starvation of seabirds and whales from combined metabolic demand and reduced prey quality associated with protracted MHWs across multiple regions ; Sydeman et al., 2015; Duffy-Anderson et al., 2019; Sanford et al., 2019; Smale et al., 2019; Suryan et al. 2021). The distribution of two economically important North American species, Bering Sea Pacific cod  and American lobster , have shifted north. The MHW-induced loss of coral reefs across tropical North American waters has varied in severity regionally. For instance, in 2015 and 2016, extensive, severe bleaching affected more than 30% of corals off the southeast USA and a large proportion of US Hawaiian Islands, but had moderate to no impact off the Mexican Yucatan Peninsula . Some reefs are exhibiting recovery following efforts focused at reducing non-climate stressors . Such MHWs are increasing in intensity and frequency  with the largest increases in frequency and spatial coverage projected for the Gulf of Mexico, US southern east coast and US Pacific Northwest  and pose a key risk to marine systems in North America .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report