NIFS said the average surface water temperature was the highest in the summer of 2023 since its observation of the surface water temperature in the Korean seas in 1990, in particular during the period of late-summer to early-fall in 2023.

The finding was the result from analyzing the 27-year-old water temperature data provided by NOAA's AVHRR on a daily basis since 1997. 

As the result of water temperature analysis on the seas around Korean peninsula from the late-August to the early-September of this year, it recorded 26.0℃ of water temperature. It was 1.6℃ higher than 24.4℃ of the average water temperature in the same period over the past 26 years (1997-2022).

The high water temperature warning in the summer of this year was issued more than three weeks late year-on-year because of the long-lasting rainy season. In addition to that, the unprecedented extreme heat was extended from mid-August, when typhoon Khanun lashed Korea, to September.