Abstract
Global climate models project the intensification of marine heatwaves in coming decades due to global warming. However, the spatial resolution of these models is inadequate to resolve mesoscale processes that dominate variability in boundary current regions where societal and economic impacts of marine heatwaves are substantial. Here we compare the historical and projected changes in marine heatwaves in a 0.1° ocean model with 23 coarser-resolution climate models. Western boundary currents are the regions where the models disagree the most with observations and among themselves in simulating marine heatwaves of the past and the future. The lack of eddy-driven variability in the coarse-resolution models results in less intense marine heatwaves over the historical period and greater intensification in the coming decades. Although the projected changes agree well at the global scale, the greater spatial details around western boundary currents provided by the high-resolution model may be valuable for effective adaptation planning.
Highlights
Global climate models project the intensification of marine heatwaves in coming decades due to global warming
We focus on the 60°S–60°N spatial comparison of the climatological state during the overlap period among Ocean Forecasting Australian Model version 3 (OFAM3), Coupled Model Intercomparison Project 5 (CMIP5), and MGD (1982–2018; Figs. 1 and 2)
Western boundary currents are regions of fast and variable currents, where a substantial fraction of marine heatwaves (MHWs) are generated by internal variability arising from local forcing and mesoscale processes, rather than large-scale climate modes[28]
Summary
Global climate models project the intensification of marine heatwaves in coming decades due to global warming. The observed increasing trend in MHWs is expected to continue through this century globally, based on projections of global climate models participating in the Coupled Model Intercomparison Project 5 (CMIP5)[10,11] These models are useful in assessing the impacts of ongoing climate change on MHWs at the global scale, the spatial resolution of many of these models is too coarse to resolve mesoscale processes that play a substantial role in the dynamics of the ocean[12]. Western boundary currents are regions of intense eddy activity where high-resolution models simulate the historical mean state and variability better than the coarse-resolution models[13]. The results of the high-resolution model simulation are compared directly with those of an observation-based daily SST analysis product of the Japan Meteorological Agency (MGD)[22] as well as the multi-model mean product of 23 global climate models (CMIP5)
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