NIFS announced that it published「A Briefing Book: 2026 Climate Change Impact on Oceans and Fisheries」that provides a comprehensive analysis on the changes in Korean waters and marine ecosystems driven by climate change. 

Built on scientific data, the briefing book is written to help fishermen and the public to easily understand the long-term changes in Korean waters and last year’s issues caused by climate change. 

Over the past 58 years, the sea surface temperatures (SSTs) in Korean waters have increased by 1.60℃ -more than double the global SST increase of 0.76℃- representing faster ocean warming. In particular, the rate of increases in water temperature for recent ten years has been more than three times higher* than the past rate, showing clear acceleration trend.

It is the result of the stronger Tsushima Warm Current coupled with the increased number of extreme heat waves** due to the expansion of high pressure in summer and recent increase in strength and frequency of marine heatwaves***. 

*The rate of increases in water temperature: 0.0276℃ per year for a long period (1968-2025), 0.09℃ per year in recent 10 years (2016-2025) 

**Marine Heatwaves warnings (Daytime highs reaching up to 33 degrees Celsius or above): (1991-2020) 11.0 days on average, (’23) 14.2 days, (’24) 30.1 days, (’25) 29.7 days 

***Marine Heatwaves are periods of persistent anomalously warm ocean temperatures 

Also, there have been distinctive structural changes across marine ecosystems. The acidification in Korean waters are under way, declines not only in dissoloved oxygen in bottom layer of the East Sea but in surface nutrients in overall Korean waters due to stratification* were also found. 

*Ocean stratification is the natural separation of the ocean into distinct horizontal layers based on density. Warm, less dense water rests at the surface, floating over cold, dense, and often saltier water. This creates a stable barrier that limits vertical mixing. 

In the first half of last year, Korean waters showed low water temperature compared to average year, but distinct high water temperature trend started to be found in overall Korean waters after late June, representing a clear contrast between the two periods.

Moreover, there has been diversification in emergence trends of harmful organisms, including harmful algal bloom outbreak in six years due to the prolonged cold water mass in the Southern East Sea coupled with increase of intensive downpours, and Porpita porpita (also known as blue button jellyfish) found in extensive areas from Jeju Island to the East Sea. 

NIFS President (Mr. Kwon Soon-wook) said, “As Korean waters experience fater warming beyond our anticipation, distinctive changes are found not only in physical aspects but in overall ecosystem. I hope this briefing book would be useful in expanding scienctific understanding on climate change and enhancing field readiness.”