The Korea Institute of Ocean Science and Technology (KIOST, President Kim Woong-seo) announced that it has identified the causes of high sea surface temperature in the West Pacific for the first time, and submitted the related thesis to Environmental Research Letters, a renowned scientific journal in the field of environmental science. 
  * Title of thesis: “Two major modes of East Asian marine heatwaves” (2020, Lee Seon-ju, Park Myung-sook, Kwon Min-ho, Kim Young-ho, Park Young-gyu)

Along with global warming, high sea surface temperature in the West Pacific is a climatic development that has attracted much attention. Sometimes, the sea surface temperature in the West Pacific is far higher than average for periods of several days or weeks, and this phenomena has been attributed to heat waves.

However, Senior Researcher Park Myung-sook of KIOST found that high sea surface temperature is actually caused by multiple factors, including atmospheric temperature, oceanic conditions, and climate changes, and divided the causes into two types.

The first type is “oceanic” causes. These arise when the temperature of the West Pacific has been rising for several months due to the disappearance of El Nino. When the ocean is sufficiently warm, high sea surface temperature can occur despite the weak effects of atmospheric pressure and heat waves.

The second type is “atmospheric” causes, which include atmospheric pressure and solar radiation. Despite the lower-than-average sea surface temperature in the West Pacific, high-pressure areas can occur due to atmospheric disturbances* caused by the longitudinal positioning of successive high-pressure areas and low-pressure areas at middle latitudes (30 to 50 degrees north) in Eurasia. When such high-pressure areas intensify, solar radiation causes the sea surface temperature to rise.
* Atmospheric disturbance refers to any agitation or disruption of the atmospheric steady state that leads to atmospheric phenomena such as a typhoon, storm, precipitation, or high- or low-pressure areas.

Until June this year, the sea surface temperature of the West Pacific had been higher than average. In July, however, the temperature fell due to the blockage of sunlight by clouds during the long rainy season, with very few instances of high sea surface temperature. In August, the temperature of the West Pacific rose again, with high-temperature, low-salinity water, caused by heavy rainfall in the southern region of China, flowing in from the East China Sea. This shows that high atmospheric pressure in East Asia can lead to temporary high sea surface temperatures in the West Pacific.

This research was conducted under the R&D project* entitled “Establishment of a system for the identification and prediction of causes of high sea surface temperature around the Korean Peninsula attributable to the subarctic West Pacific,” which is supported by the Ministry of Oceans and Fisheries. The researchers analyzed and identified causes of high sea surface temperature in East Asian seas using OISST** data of the NOAA spanning the 40-year period from 1982 to 2018.
* Project cost: KRW 15 billion (2020: KRW 2.33 billion) / Period: 2019 to 2013 / Institution in charge: Korea Polar Research Institute of KOIST 
 ** OISST (Optimum Interpolation Sea Surface Temperature) is an analysis conducted by combining observations from different sources (satellites, ships, buoys, etc.) on a regular global grid.

Senior Researcher Park Myung-sook said, “By identifying the causes of high sea surface temperature, signs of abnormal weather events can be predicted earlier, thereby reducing damages to the fishing industry. Going forward, we will continue enhancing the accuracy of marine weather forecasts by analyzing the causes of various oceanic phenomena through the use of research vessels and communication, marine observation, and meteorological satellites.”