World map showing several marine heatwaves at different locations in August and September 2023. The marine heatwave west of South America is a prominent example.
Major marine heatwaves have occurred for example in the Great Barrier Reef in 2002,[15] in the Mediterranean Sea in 2003,[10] in the Northwest Atlantic in 2012,[2][16] and in the Northeast Pacific during 2013–2016.[17][18] These events have had drastic and long-term impacts on the oceanographic and biological conditions in those areas.[10][19][9]
Scientists predict that the frequency, duration, scale (or area) and intensity of marine heatwaves will continue to increase.[20]: 1227 This is because sea surface temperatures will continue to increase with global warming. 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).".[22]: 67 The extent of ocean warming depends on greenhouse gas emission scenarios, and thus humans' climate change mitigation efforts. Scientists predict that marine heatwaves will become "four times more frequent in 2081–2100 compared to 1995–2014" under the lower greenhouse gas emissions scenario, or eight times more frequent under the higher emissions scenario.[20]: 1214
^Cite error: The named reference :0 was invoked but never defined (see the help page).
^ abcGarrabou, J.; Coma, R.; Bensoussan, N.; Bally, M.; Chevaldonné, P.; Cigliano, M.; Diaz, D.; Harmelin, J. G.; Gambi, M. C.; Kersting, D. K.; Ledoux, J. B. (May 2009). "Mass mortality in Northwestern Mediterranean rocky benthic communities: effects of the 2003 heat wave". Global Change Biology. 15 (5): 1090–1103. Bibcode:2009GCBio..15.1090G. doi:10.1111/j.1365-2486.2008.01823.x. S2CID55566218.
^IPCC, 2019: Technical Summary [H.-O. Pörtner, D.C. Roberts, V. Masson-Delmotte, P. Zhai, E. Poloczanska, K. Mintenbeck, M. Tignor, A. Alegría, M. Nicolai, A. Okem, J. Petzold, B. Rama, N.M. Weyer (eds.)]. In: IPCC Special Report on the Ocean and Cryosphere in a Changing Climate [H.- O. Pörtner, D.C. Roberts, V. Masson-Delmotte, P. Zhai, M. Tignor, E. Poloczanska, K. Mintenbeck, A. Alegría, M. Nicolai, A. Okem, J. Petzold, B. Rama, N.M. Weyer (eds.)]. Cambridge University Press, Cambridge, UK and New York, NY, USA, pp. 39–69. https://doi.org/10.1017/9781009157964.002