[A-CG36] Satellite Earth Environment Observation

[ACG36-P02] Marine Heatwave and Cold-Spell Events Adjacent to Taiwan

*Jia-Yu Lin¹, Po-Chun Hsu¹ (1.Center for Space and Remote Sensing Research, National Central University)

Keywords:Marine Heatwave, Marine Cold-Spell, Climate Change, Global Warming, Extreme Climate

Marine heatwaves (MHWs) are phenomena characterized by a sudden and significant increase in sea surface temperature (SST), while marine cold-spells (MCSs) involve a sudden and significant decrease in SST. In recent years, the analysis methods and related issues of MHWs and MCSs have begun to receive attention. In this study, an MHW event is defined as occurring when the SST at a specific location exceeds the 90th percentile of the daily SST for the same location during the 30-year climate base period from 1985 to 2014, persisting for five days or more. Conversely, an MCS is defined using the 10th percentile of the same climate base period as the threshold, also requiring persistence below this threshold for five days or more. This research utilizes daily global 5km satellite coral bleaching heat stress monitoring SST data from 1985 to 2022, spanning 38 years, to calculate the frequency, duration, onset, decline, maximum intensity, cumulative intensity, average intensity, and other indicators as reference values for event characteristic classification of MHW and MCS. The study analyzes the spatial distribution of different event classifications in the seas surrounding Taiwan and the spatial distribution of various indicators under different climatic conditions. This helps to understand the impact of different physical conditions in the seas around Taiwan on MHW and MCS events. Between 1985 and 2022, the average annual duration of events indicates that MHWs (50.5 days) are more frequent than MCSs (31.2 days). However, in terms of trends, both the maximum intensity and annual duration show that the increase in MHWs (0.015℃/year, 2.4 days/year) is greater than that of MCSs (0.004 ℃/year, -0.96 days/year). Influenced by global warming, the rising global sea temperatures lead to continuous increases in MHW average intensity (0.02 ℃/decade), frequency (1.2 times/decade), and duration (2.4 days/decade). In contrast, MCSs show a slight increase only in average intensity (-0.04 ℃/decade), while frequency (-1.0 times/decade) and duration (-0.03 days/decade) exhibit decreasing trends in these three indicators. Additionally, we divided the seas around Taiwan into smaller regions to analyze the reasons for their spatiotemporal variations.