Marine heatwaves in global sea surface temperature records since 1850

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The adverse impacts of marine heatwaves (MHWs) on marine ecosystems and human activities are well-documented, yet observational studies tend to largely rely on recent records. Long-term records of MHWs can put the recent increase in frequency and intensity of MHWs in the context of past variability. We used long-term monthly sea surface temperature data and night marine air temperatures to characterise past MHW activity. A persistent increase in the global extent of MHWs is demonstrated, beginning around 1970. The average annual MHW extent post-2010 is estimated to be increased at least 4-fold compared to that pre-1970. A strong correlation between spatial variability of recorded monthly SSTs and the inverse root of average number of monthly observations implies both frequency and amplitude of MHWs is overestimated when the number of monthly observations is low. Nevertheless, many identified early MHWs appear genuine, such as a multi-month event in the North Atlantic in 1851-1852. MHWs are also affected by poorer sampling during the world wars. The most extensive MHW years globally coincide with El Niño years, and MHW extent in the North Atlantic is correlated with the AMO.
Original languageEnglish
Article number084027
JournalEnvironmental Research Letters
Issue number8
Early online date18 Jul 2022
Publication statusPublished - 1 Aug 2022


  • AMO
  • El Nino
  • climate change
  • extreme events
  • marine heatwaves
  • sea surface temperature


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