The global ocean has warmed substantially over the past century, with far-reaching implications for marine ecosystems1. Concurrent with long-term persistent warming, discrete periods of extreme regional ocean warming (marine heatwaves, MHWs) have increased in frequency2. Here we quantify trends and attributes of MHWs across all ocean basins and examine their biological impacts from species to ecosystems. Multiple regions in the Pacific, Atlantic and Indian Oceans are particularly vulnerable to MHW intensification, due to the co-existence of high levels of biodiversity, a prevalence of species found at their warm range edges or concurrent non-climatic human impacts. The physical attributes of prominent MHWs varied considerably, but all had deleterious impacts across a range of biological processes and taxa, including critical foundation species (corals, seagrasses and kelps). MHWs, which will probably intensify with anthropogenic climate change3, are rapidly emerging as forceful agents of disturbance with the capacity to restructure entire ecosystems and disrupt the provision of ecological goods and services in coming decades.

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Data availability

Daily 0.25° resolution NOAA OISST V2 data are provided by the NOAA/OAR/ESRLPSD, Boulder, Colorado, USA, at http://www.esrl.noaa.gov/psd/. Data on human impacts and marine biodiversity are available from NCEAS (https://www.nceas.ucsb.edu/globalmarine) and Aquamaps (www.aquamaps.org), respectively. Coral bleaching records were extracted from the NOAA Reef Watch programme (https://coralreefwatch.noaa.gov), giant kelp biomass data were sourced from the Santa Barbara Coastal Long-term Ecological Research (SBC-LTER) programme (http://sbc.lternet.edu//index.html). Additional data are available from the corresponding author upon request.

Additional information

Journal peer review information: Nature Climate Change thanks Jennifer Jackson and Paul Fiedler for their contribution to this work.

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Change history

  • 18 March 2019

    In the version of this Letter originally published, the following ‘Journal peer review information’ was missing “Nature Climate Change thanks Jennifer Jackson and Paul Fiedler for their contribution to the peer review of this work.” This statement has now been added.


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Concepts and analyses were developed during three workshops organized by an international working group on marine heatwaves (www.marineheatwaves.org). Workshops were primarily funded by a University of Western Australia Research Collaboration Award to T.W. and a Natural Environment Research Council (UK) International Opportunity Fund awarded to D.A.S. (NE/N00678X/1). D.A.S. is supported by an Independent Research Fellowship (NE/K008439/1) awarded by the Natural Environment Research Council (UK). The Australian Research Council supported T.W. (FT110100174 and DP170100023), E.C.J.O. (CE110001028) and M.G.D. (DE150100456). N.J.H. and L.V.A. are supported by the ARC Centre of Excellence for Climate Extremes (CE170100023). M.S.T was supported by the Brian Mason Trust. P.J.M. is supported by a Marie Curie Career Integration Grant (PCIG10-GA-2011–303685) and a Natural Environment Research Council (UK) Grant (NE/J024082/1). S.C.S. was supported by an Australian Government RTP Scholarship. This work contributes to the World Climate Research Programme Grand Challenge on Extremes, the NESP Earth Systems and Climate Change Hub Project 2.3 (Component 2) on the predictability of ocean temperature extremes, and the interests and activities of the International Commission on Climate of IAMAS/IUGG.

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Author notes

  1. These authors contributed equally: Dan A. Smale and Thomas Wernberg.


  1. Marine Biological Association of the United Kingdom, The Laboratory, Citadel Hill, Plymouth, UK

    • Dan A. Smale
  2. UWA Oceans Institute and School of Biological Sciences, The University of Western Australia, Crawley, Western Australia, Australia

    • Dan A. Smale
    • , Thomas Wernberg
    •  & Sandra C. Straub
  3. Department of Oceanography, Dalhousie University, Halifax, Nova Scotia, Canada

    • Eric C. J. Oliver
  4. Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia

    • Eric C. J. Oliver
    •  & Neil J. Holbrook
  5. Australian Research Council Centre of Excellence for Climate System Science, University of Tasmania, Hobart, Tasmania, Australia

    • Eric C. J. Oliver
  6. Centre of Integrative Ecology and Marine Ecology Research Group, School of Biological Sciences, University of Canterbury, Private Bag, Christchurch, New Zealand

    • Mads Thomsen
  7. Institute of Biological, Environmental and Rural Sciences, Aberystwyth University, Aberystwyth, UK

    • Ben P. Harvey
    •  & Pippa J. Moore
  8. Shimoda Marine Research Center, University of Tsukuba, Shizuoka, Japan

    • Ben P. Harvey
  9. Department of Ecology, Scottish Association for Marine Science, Scottish Marine Institute, Oban, Argyll, UK

    • Michael T. Burrows
    •  & Ben L. Payne
  10. Climate Change Research Centre, The University of New South Wales, Sydney, New South Wales, Australia

    • Lisa V. Alexander
    • , Markus G. Donat
    • , Sarah E. Perkins-Kirkpatrick
    •  & Alex Sen Gupta
  11. Australian Research Council Centre of Excellence for Climate Extremes, The University of New South Wales, Sydney, New South Wales, Australia

    • Lisa V. Alexander
    • , Markus G. Donat
    • , Sarah E. Perkins-Kirkpatrick
    •  & Alex Sen Gupta
  12. Australian Research Council Centre of Excellence for Climate System Science, The University of New South Wales, Sydney, New South Wales, Australia

    • Lisa V. Alexander
  13. Australian Institute of Marine Science, Crawley, Western Australia, Australia

    • Jessica A. Benthuysen
  14. Barcelona Supercomputing Center, Barcelona, Spain

    • Markus G. Donat
  15. CSIRO Oceans and Atmosphere, Crawley, Western Australia, Australia

    • Ming Feng
  16. CSIRO Oceans and Atmosphere, Hobart, Tasmania, Australia

    • Alistair J. Hobday
  17. Australian Research Council Centre of Excellence for Climate Extremes, University of Tasmania, Hobart, Tasmania, Australia

    • Neil J. Holbrook
  18. School of Oceanography, University of Washington, Seattle, WA, USA

    • Hillary A. Scannell
  19. Centre for Marine Ecosystems Research, School of Natural Sciences, Edith Cowan University, Joondalup, Western Australia, Australia

    • Pippa J. Moore


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D.A.S. and T.W. conceived the initial idea. All authors contributed intellectually to its development. D.A.S., T.W., E.C.J.O. and N.J.H. co-convened the workshops. E.C.J.O. led the development of the M.H.W. analysis, which was supported by N.J.H., L.V.A., J.A.B., M.G.D., M.F., A.J.H., S.E.P.-K., H.A.S. and A.S.G. The meta-analysis of ecological impacts was conducted by M.T., B.P.H., S.C.S., M.T.B. and P.J.M. D.A.S. led manuscript preparation with input from all authors.

Competing interests

The authors declare no competing interests.

Corresponding author

Correspondence to Dan A. Smale.

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