Abstract
Marine heatwaves (MHWs), episodic periods of abnormally high sea surface temperature, severely affect marine ecosystems. Large marine ecosystems (LMEs) cover ~22% of the global ocean but account for 95% of global fisheries catches. Yet how climate change affects MHWs over LMEs remains unknown because such LMEs are confined to the coast where low-resolution climate models are known to have biases. Here, using a high-resolution Earth system model and applying a ‘future threshold’ that considers MHWs as anomalous warming above the long-term mean warming of sea surface temperatures, we find that future intensity and annual days of MHWs over the majority of the LMEs remain higher than in the present-day climate. Better resolution of ocean mesoscale eddies enables simulation of more realistic MHWs than low-resolution models. These increases in MHWs under global warming pose a serious threat to LMEs, even if resident organisms could adapt fully to the long-term mean warming.
Highlights
The ocean has warmed substantially during the past few decades in most parts of the world[1]
Under the fossil fuel-intensive scenario of representative concentration pathway (RCP) 8.5, the majority of ocean areas is projected to experience almost permanent heatwaves with concomitantly stronger intensity by the end of the twenty-first century, with marine heatwaves (MHWs) defined on the basis of the conditions of the present climate[17], referred to as a mean warming-inclusive threshold
The mean warming dominates the changes in MHWs and explains 94% or more of the simulated changes, as inferred by the similarity between the changes directly estimated from the simulations (Fig. 4c,d) and the changes calculated on the basis of the pseudo scenario with mean warming alone (Extended Data Fig. 3)
Summary
Our result is based on a high-fidelity simulation using a high-resolution model that provides improved simulation of MHWs in the LME regions. As computational power continues to improve, we expect that a multimodel ensemble of high-resolution model simulations will soon be possible to project future MHW changes under multiple climate-forcing scenarios, to assess the associated uncertainty and to provide early warning of the likely changes. Online content Any methods, additional references, Nature Research reporting summaries, source data, extended data, supplementary information, acknowledgements, peer review information; details of author contributions and competing interests; and statements of data and code availability are available at https://doi.org/10.1038/ s41558-021-01266-5. Received: 22 July 2021; Accepted: 13 December 2021; Published online: 3 February 2022
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