17:15 〜 18:45
[AOS15-P04] 琉球列島周辺海域における高水温イベントとサンゴ白化
キーワード：サンゴ白化、週積算水温、海洋熱波
The warming ocean surface waters can lead to bleaching of corals, which is the process that corals loss their symbiotic dinoflagellate algae. The IPCC Sixth Assessment Report in 2022 described that: "Since the early 1980s, the frequency and severity of mass coral bleaching events have increased sharply worldwide". It is expected that many coral reefs will undergo irreversible phase shifts due to marine heatwaves with global warming. Marine heat wave, however, is high temperature anomaly events and could appear all year round, while temperature in summer would be more important for coral bleaching around the Ryukyu Islands since ocean temperature show significant seasonal cycle there. Here we describe high temperature events, high temperature anomaly events and coral bleaching around the Ryukyu Islands, and elucidate the relationship among them. We also discuss the relationship with the large scale climate variability such as El Nino/Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD).
More than 99% of the high temperature events occurred from June to October, and more than 80% did from July to September, while high temperature anomaly events occurred all year around. In June to October, more than 10% of the data reported overall bleaching in average, and more than 25% did partial bleaching. In August, bleaching was reported in more than 40%, and about 50% among them was categorized to overall bleaching. Spatial distribution of the coral bleaching also corresponds well with the high temperature events than the high temperature anomaly events. In 2016, the extensive and severe coral bleaching was reported around the Okinawa, Miyako, and Yaeyama Islands, where the strong high temperature event occurred. When the high temperature events occurred around the Ryukyu Islands, SST in the central to eastern equatorial Pacific shows negative anomaly and that in the eastern Indian Ocean shows positive anomaly, which indicates the relation with La Niña and the negative IOD.
More than 99% of the high temperature events occurred from June to October, and more than 80% did from July to September, while high temperature anomaly events occurred all year around. In June to October, more than 10% of the data reported overall bleaching in average, and more than 25% did partial bleaching. In August, bleaching was reported in more than 40%, and about 50% among them was categorized to overall bleaching. Spatial distribution of the coral bleaching also corresponds well with the high temperature events than the high temperature anomaly events. In 2016, the extensive and severe coral bleaching was reported around the Okinawa, Miyako, and Yaeyama Islands, where the strong high temperature event occurred. When the high temperature events occurred around the Ryukyu Islands, SST in the central to eastern equatorial Pacific shows negative anomaly and that in the eastern Indian Ocean shows positive anomaly, which indicates the relation with La Niña and the negative IOD.