Longer and more frequent marine heatwaves over the past century

Eric C J Oliver,Thomas Wernberg,Jessica A Benthuysen,Sarah E Perkins-Kirkpatrick,Alistair J Hobday,Lisa V Alexander,Alex Sen Gupta,Hillary A Scannell,Ming Feng,Pippa J Moore,Dan A Smale,Michael T Burrows,Sandra C Straub,Neil J Holbrook,Markus G Donat

doi:10.1038/s41467-018-03732-9

Abstract

Heatwaves are important climatic extremes in atmospheric and oceanic systems that can have devastating and long-term impacts on ecosystems, with subsequent socioeconomic consequences. Recent prominent marine heatwaves have attracted considerable scientific and public interest. Despite this, a comprehensive assessment of how these ocean temperature extremes have been changing globally is missing. Using a range of ocean temperature data including global records of daily satellite observations, daily in situ measurements and gridded monthly in situ-based data sets, we identify significant increases in marine heatwaves over the past century. We find that from 1925 to 2016, global average marine heatwave frequency and duration increased by 34% and 17%, respectively, resulting in a 54% increase in annual marine heatwave days globally. Importantly, these trends can largely be explained by increases in mean ocean temperatures, suggesting that we can expect further increases in marine heatwave days under continued global warming.

Highlights

Heatwaves are important climatic extremes in atmospheric and oceanic systems that can have devastating and long-term impacts on ecosystems, with subsequent socioeconomic consequences
We find significant secular increases in both the frequency and duration of marine heatwaves, amounting globally to a 54% increase in annual marine heatwave days between 1925–1954 and 1987–2016
The most notable exception was in the eastern tropical Pacific, where El NiñoSouthern Oscillation (ENSO) events manifest as individual longduration marine heatwaves (MHWs) and resulted in less than one MHW per year on average

Summary

Introduction

Heatwaves are important climatic extremes in atmospheric and oceanic systems that can have devastating and long-term impacts on ecosystems, with subsequent socioeconomic consequences. Notable events occurred in the northern Mediterranean Sea in 20032,3, along the Western Australian coast in 20114, the northwest Atlantic in 20125, the northeast Pacific over 2013–20156,7, off southeastern Australia in 2015/168 and across northern Australia in 20169 These events resulted in substantial ecological and economic impacts, including sustained loss of kelp forests[10], coral bleaching[11], reduced surface chlorophyll levels due to increased surface layer stratification[6], mass mortality of marine invertebrates due to heat stress[8,12], rapid long-distance species’ range shifts and associated reshaping of community structure[8,10,13], fishery closures or quota changes[8,13,14] and even intensified economic tensions between nations[15]. While centennial increases in ocean surface temperatures have been extensively reported[35,36], global trends in ocean temperature extremes remain largely unexplored

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