Record sea temperatures around the Japanese archipelago reach historic highs

According to information provided by Japanese media, this year witnessed a record-high average temperature of the waters surrounding the Japanese archipelago.

"Asahi Shimbun" journalists analyzed data provided by the Japan Meteorological Agency concerning the average surface temperatures of the waters. The data were collected based on readings from 10 marine areas taken every 10 days for the past 43 years.

The analysis shows that the average temperature of these areas from January to June this year was 65°F. This means it was 0.47°F higher than the previous record in 1998 and 1.91°F higher than the average from 1991 to 2020, which is considered "normal."

"Asahi Shimbun" emphasizes that the water temperature in the area stretching east of Hokkaido island, north of the archipelago, was 4.28°F higher than usual in the first half of the year.

Toru Miyama, a marine physicist from the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), believes this results from the change in direction and northward extension of the Kuroshio (known as the Japan Current), which brings warmer waters from the south. The scientist adds that this phenomenon is also related to global warming.

This change has already impacted fishing, among other things, forcing the fishing season to start a week later compared to the previous year.

- Due to rising sea temperatures, salmon and trout have become almost impossible to catch at the end of the fishing season in recent years - said Kazuhiko Nakajima, director of a fishermen's association based in Sapporo, to the newspaper.

One cause of these anomalies in fishing grounds is "ocean heat waves," a statistically rare phenomenon in which high sea temperatures persist for more than five days.

"Asahi Shimbun" reminds that in the fall of 2021, the eastern coast of Hokkaido was hit by the worst "red tide" ever recorded, causing the death of vast numbers of sea urchins, salmon, and octopuses.