Marine heatwave
[5][6] For example, marine heatwaves can lead to severe biodiversity changes such as coral bleaching, sea star wasting disease,[7][8] harmful algal blooms,[9] and mass mortality of benthic communities.
The IPCC Sixth Assessment Report in 2022 has summarized research findings to date and stated 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".
[21]: 381 This confirms earlier findings in a report by the IPCC in 2019 which had found that "marine heatwaves [...] have doubled in frequency and have become longer lasting, more intense and more extensive (very likely).".
"[1] Another publication defined it as follows: an anomalously warm event is a marine heatwave "if it lasts for five or more days, with temperatures warmer than the 90th percentile based on a 30-year historical baseline period".
[23] The term marine heatwave was coined following an unprecedented warming event off the west coast of Australia in the austral summer of 2011, which led to a rapid dieback of kelp forests and associated ecosystem shifts along hundreds of kilometers of coastline.
The category applied to each event in real-time is defined primarily by sea surface temperature anomalies (SSTA), but over time it comes to include typology and characteristics.
[25][2][4] At the local level marine heatwave events are dominated by ocean advection, air-sea fluxes, thermocline stability, and wind stress.
[27] For marine heatwave, the teleconnection process that play a dominant role are atmospheric blocking/subsidence, jet-stream position, oceanic kelvin waves, regional wind stress, warm surface air temperature, and seasonal climate oscillations.
Scientists have calculated this as follows: there would be a relatively small (but still significant) increase of 0.86 °C in the average sea surface temperature for the low emissions scenario (called SSP1-2.6).
[32] Sea surface temperatures have been recorded since 1904 in Port Erin, Isle of Man,[4] and measurements continue through global organizations such as NOAA, NASA, and many more.
[10][19][7] Climate change-related exceptional marine heatwaves in the Mediterranean Sea during 2015–2019 resulted in widespread mass sealife die-offs in five consecutive years.
[40] Repeated marine heatwaves in the Northest[clarification needed] Pacific led to dramatic changes in animal abundances, predator-prey relationships, and energy flux throughout the ecosystem.
[29]: 610 Extreme bleaching events are directly linked with climate-induced phenomena that increase ocean temperature, such as El Niño-Southern Oscillation (ENSO).
The IPCC Sixth Assessment Report in 2022 found that: "Since the early 1980s, the frequency and severity of mass coral bleaching events have increased sharply worldwide".
[42]: 416 Coral reefs, as well as other shelf-sea ecosystems, such as rocky shores, kelp forests, seagrasses, and mangroves, have recently undergone mass mortalities from marine heatwaves.
[42]: 381 It is expected that many coral reefs will "undergo irreversible phase shifts due to marine heatwaves with global warming levels >1.5°C".
