Marine heatwaves in the Western North Pacific Region: Historical characteristics and future projections

This study investigates the historical characteristics and future trends of marine heatwaves (MHWs) in the Western North Pacific (WNP) region. During the historical period from 1982 to 2014, the WNP region experiences an average MHW frequency of 0.89 +/- 0.18 count/year. These events have an average duration of 8.64 +/- 1.39 days/count. Annually, the cumulative MHW days amount to 7.76 +/- 2.23 days, with an accumulated intensity of 15.73 +/- 6.43 degrees C days. The maximum intensity recorded during this period reaches 2.04 +/- 0.54 degrees C, while the average intensity stands at 1.74 +/- 0.48 degrees C/count. In the evaluation of 14 CMIP6 models, five optimal models, namely GFDL-ESM4, EC-Earth3-Veg, EC-Earth3, BCC-CSM2-MR, and MRI-ESM2-0, are selected for simulating future MHWs. Based on the simulation results of these five models under the SSP2-4.5 and SSP5-8.5 scenarios for the future period (2015-2100), it is found that under the SSP2-4.5, the frequency of MHWs is slightly higher compared to the SSP5-8.5. However, under the SSP5-8.5, MHWs exhibit higher accumulated intensity, maximum intensity, and average intensity, with a predominance of high-intensity MHWs in the Kuroshio Extension region. The occurrence area ratio in the future is significantly larger than in the historical period. Moreover, MHWs intensity displays a seasonal variation, with stronger during summer and weaker during winter. This study provides important insights into MHWs in the WNP region, offering valuable information for decision-makers in formulating response measures and reducing economic losses.