Environment Sea temperatures around Japan remain on record level

Surface ocean temperatures near the Japanese archipelago have reached a record high from June to February for the third consecutive year. This has negative implications for the fisheries and aquaculture industries. According to the Japan Meteorological Agency, this three-year streak of record-high temperatures is the first occurrence since they began tracking surface sea temperatures in 1982. In 2023, the average ocean surface temperature near Japan was 1 degree higher between June and August compared to the usual conditions based on the 30-year average from 1991 to 2020.


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As for the September-November period and the December-February period, the water temperature was 1.9 degrees higher and 1.1 degrees higher, respectively. The largest difference of 0.8 degree in the surface ocean temperature in the June-August period, compared with the normal, was recorded in 2022. The largest disparity for the September-November period came in 1998 and 1999, when it was 0.7 degree. For the December-February period, the biggest discrepancy of 0.7 degree was logged in 1999. The record was set as Japan and elsewhere recorded unusually high temperatures last year. According to the agency, the average temperatures for 2023 in the northern and northeastern regions were the highest since the agency began collecting data in 1946. As for western Japan, the mercury reading was on par with the highest recorded.

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The Black Current:

JMA said higher temperatures were particularly noticeable on the eastern coastline of the main island of Honshu due to global warming and a shift in the direction of the Black Current. The Black Current, a warm current flowing from south to north, changes its direction eastward and flows away from Japan after approaching the Boso Peninsula, which separates Tokyo Bay from the Pacific Ocean. But since spring 2023, the Black Current has continued to flow along the coast of the northeastern Tohoku region rather than travelling eastward.