A global assessment of marine heatwaves and their drivers

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

doi:10.1038/s41467-019-10206-z

Cited by 447 publications

(562 citation statements)

References 83 publications

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“…coverage (e.g., Frölicher & Laufkötter, 2018;Hobday et al, 2016;Holbrook et al, 2019;Manta et al, 2018;Oliver et al, 2017;Smale et al, 2019). The results relative to NOAA-OI presented here are comparable to previous MHW studies-because the same biases are present in those studies.…”

Section: Observationssupporting

confidence: 86%

“…Other sources of bias are atmospheric aerosols, and instrument design and aging. Despite these biases, NOAA‐OI has been widely used in MHW studies due to its temporal and spatial resolution, long record, and global coverage (e.g., Frölicher & Laufkötter, ; Hobday et al, ; Holbrook et al, ; Manta et al, ; Oliver et al, ; Smale et al, ). The results relative to NOAA‐OI presented here are comparable to previous MHW studies—because the same biases are present in those studies.…”

Section: Methodsmentioning

confidence: 99%

“…The occurrence of sustained temperature extremes leads to marine heatwave (MHW) conditions in the ocean (Hobday et al, ). MHW conditions are caused by local processes that directly affect ocean temperature, such as extreme air‐sea heat fluxes and changes in the ocean circulation (Behrens et al, ; Holbrook et al, ; Salinger et al, ), which may ultimately be caused by large‐scale climate forcing via teleconnection processes (Holbrook et al, ).…”

Section: Introductionmentioning

confidence: 99%

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Sensitivity of Marine Heatwave Metrics to Ocean Model Resolution

Pilo

Holbrook

Kiss

et al. 2019

Geophysical Research Letters

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Sustained extreme temperature events in the ocean, referred to as marine heatwaves (MHWs), generate substantial ecological, social, and economic impacts. Ocean models provide insights to the drivers, persistence, and dissipation of MHWs. However, the sensitivity of MHW metrics to ocean model resolution is unknown. Here, we analyze global MHW metrics in three configurations of a global ocean-sea ice model at coarse (1 • ), eddy-permitting (0.25 • ), and eddy-rich (0.1 • ) resolutions. We show that all configurations qualitatively represent broad-scale global patterns of MHWs. These simulated MHWs are, however, weaker, longer-lasting, and less frequent than in observations. The 0.1 • configuration, despite local biases, performs best both globally and regionally. Based on these results, model projections of future MHW metrics using coarse-resolution models are expected to be biased toward weaker and less frequent MHWs, when compared with results using an eddy-rich model. Plain Language SummaryMarine heatwaves (MHWs) are persistent extreme temperatures in the ocean. They have a negative impact on marine life, fisheries, and tourism, and are becoming more frequent and more intense. One way to understand how MHWs form, intensify, and decay is by analyzing results from computer simulations of the ocean. However, these simulations are a simplification of reality, and depending on how they are designed they represent different aspects of the ocean circulation. It is still unknown how much the resolution of an ocean simulation matters when representing MHWs. In this work, we compare the performance of three ocean simulations-with low, medium, and high resolutions-when representing MHWs. We find that, regardless of their resolution, all simulations have weaker, longer, and less-frequent MHWs, when compared with the real world. Despite these differences, we find that simulations with medium and high-resolutions realistically represent global spatial patterns of MHWs. However, the ocean simulation with high resolution is preferable when studying regional patterns of MHWs. These results show how simulated MHWs differ from the real world, helping us to improve ocean simulations to be more realistic. In addition, we now better understand how computer simulations of future oceans, under climate change conditions, represent these extreme events. Key Points:• Marine heatwaves are weaker, longer-lasting, and less frequent in models than in observations • The higher the model resolution, the less biased the marine heatwave metrics • Eddy-permitting models can be used for global marine heatwave analyses, but eddy-rich models are optimal for regional analyses

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Section: Observationssupporting

confidence: 86%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Sensitivity of Marine Heatwave Metrics to Ocean Model Resolution

Pilo

Holbrook

Kiss

et al. 2019

Geophysical Research Letters

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“…In addition, MHW intensity -the associated sea surface temperature (SST) anomaly -has increased significantly since the start of the satellite era in 1982 . The physical processes driving MHWs are varied and include air-sea heat fluxes coinciding with atmospheric heat waves and/or horizontal temperature advection due to changes in ocean circulation (Sparnocchia et al, 2006;Chen et al, 2014;Oliver et al, 2017;Holbrook et al, 2019). Regardless of the physical mechanisms driving individual MHWs, consensus is emerging that anthropogenic climate change has significantly increased the likelihood of recent MHWs including the 2015/16 Tasman Sea MHW (Oliver et al, 2017), the 2016 Northern Australia MHW (Lewis and Mallela, 2018;Oliver et al, 2018b), the 2016 Gulf of Alaska and Bering Sea MHW (Oliver et al, 2018b;Walsh et al, 2018), the 2016 California Current MHW (Jacox et al, 2018), and the 2017/18 Tasman Sea MHW (Perkins-Kirkpatrick et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Projected Marine Heatwaves in the 21st Century and the Potential for Ecological Impact

et al. 2019

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Marine heatwaves (MHWs) are extreme climatic events in oceanic systems that can have devastating impacts on ecosystems, causing abrupt ecological changes and socioeconomic consequences. Several prominent MHWs have attracted scientific and public interest, and recent assessments have documented global and regional increases in their frequency. However, for proactive marine management, it is critical to understand how patterns might change in the future. Here, we estimate future changes in MHWs to the end of the 21st century, as simulated by the CMIP5 global climate model projections. Significant increases in MHW intensity and count of annual MHW days are projected to accelerate, with many parts of the ocean reaching a near-permanent MHW state by the late 21st century. The two greenhouse gas (GHG) emission scenarios considered (Representative Concentration Pathway 4.5 and 8.5) strongly affect the projected intensity of MHW events, the proportion of the globe exposed to permanent MHW states, and the occurrence of the most extreme MHW events. Comparison with simulations of a natural world, without anthropogenic forcing, indicate that these trends have emerged from the expected range of natural variability within the first half of the 21st century. This discrepancy implies a degree of "anthropogenic emergence," with a departure from the natural MHW conditions that have previously shaped marine ecosystems for centuries or even millennia. Based on these projections we expect impacts on marine ecosystems to be widespread, significant and persistent through the 21st century.

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“…Some of the most immediate consequences of rapidly emerging episodic heat stress events include altered commercial fish stocks, changes to planktonic communities, species redistributions, coastal expansion of toxic algal blooms, and increasing instances of disease outbreaks (Bodin, 2017;Filbee-Dexter & Wernberg, 2018;Hobday, Cochrane, et al, 2016;McCabe et al, 2016;Paerl, 2018;Pecl et al, 2017). This body of evidence increasingly suggests that extreme events, such as marine heat waves, drive episodic, severe degradation of marine ecosystems which can abruptly compromise the ecological and societal benefits that these systems provide (Frölicher & Laufkötter, 2018;Hobday, Cochrane, et al, 2016;Holbrook et al, 2019;Hughes et al, 2017;Oliver et al, 2018;Ummenhofer & Meehl, 2017;Wernberg et al, 2016). Furthermore, novel pressures driven by the emergence of unique combinations of oceanic ecosystem drivers (including acidification, warming, hypoxia, reduced nutrient supply) will likely occur within the coming decades (Henson et al, 2017), placing additional stress not only on substantially altered marine ecosystems but also on efforts to counteract ecosystem declines.…”

Section: Introductionmentioning

confidence: 99%

How do we overcome abrupt degradation of marine ecosystems and meet the challenge of heat waves and climate extremes?

Ainsworth

Hurd

Gates

et al. 2019

Global Change Biology

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Extreme heat wave events are now causing ecosystem degradation across marine ecosystems. The consequences of this heat‐induced damage range from the rapid loss of habitat‐forming organisms, through to a reduction in the services that ecosystems support, and ultimately to impacts on human health and society. How we tackle the sudden emergence of ecosystem‐wide degradation has not yet been addressed in the context of marine heat waves. An examination of recent marine heat waves from around Australia points to the potential important role that respite or refuge from environmental extremes can play in enabling organismal survival. However, most ecological interventions are being devised with a target of mid to late‐century implementation, at which time many of the ecosystems, that the interventions are targeted towards, will have already undergone repeated and widespread heat wave induced degradation. Here, our assessment of the merits of proposed ecological interventions, across a spectrum of approaches, to counter marine environmental extremes, reveals a lack preparedness to counter the effects of extreme conditions on marine ecosystems. The ecological influence of these extremes are projected to continue to impact marine ecosystems in the coming years, long before these interventions can be developed. Our assessment reveals that approaches which are technologically ready and likely to be socially acceptable are locally deployable only, whereas those which are scalable—for example to features as large as major reef systems—are not close to being testable, and are unlikely to obtain social licence for deployment. Knowledge of the environmental timescales for survival of extremes, via respite or refuge, inferred from field observations will help test such intervention tools. The growing frequency of extreme events such as marine heat waves increases the urgency to consider mitigation and intervention tools that support organismal and ecosystem survival in the immediate future, while global climate mitigation and/or intervention are formulated.

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A global assessment of marine heatwaves and their drivers

Cited by 447 publications

References 83 publications

Sensitivity of Marine Heatwave Metrics to Ocean Model Resolution

Sensitivity of Marine Heatwave Metrics to Ocean Model Resolution

Projected Marine Heatwaves in the 21st Century and the Potential for Ecological Impact

How do we overcome abrupt degradation of marine ecosystems and meet the challenge of heat waves and climate extremes?

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