[A-CG36] 中緯度大気海洋相互作用

[ACG36-06] Extreme northward meander of the Kuroshio Extension in 2023 in an eddying OGCM

*野中 正見¹、木戸 晶一郎¹ (1.国立研究開発法人海洋研究開発機構アプリケーションラボ)

キーワード：黒潮続流、蛇行、渦解像海洋大循環モデル、海洋内部変動

In 2023, an extreme northward meander of the Kuroshio Extension was observed in its upstream region. Such anomalous meander induced warm sea surface temperature anomalies (SSTAs) to the east of northern Japan, and it was found that the warm SSTAs affected surface air temperature aloft, inducing the record-breaking hot summer over northern Japan. In the present study, we investigate possible mechanisms of the extreme northward meander based on ensemble hindcast simulation with an eddying OGCM, JCOPE-FGO, with 10 ensemble members with slightly different initial conditions on January 1^st, 1993. Several ensemble members represent the extreme northward meander in 2023 closely resembling the observed one, while others displayed a significantly weaker northward meander. In this particular model, the probability of the extreme northward meander is higher in the 2020s. This is associated with the northward shift of the ensemble mean of the axis of the Kuroshio Extension from the late 2010s. The model results suggest that oceanic intrinsic variability of the Kuroshio Extension in addition to the atmospheric-driven northward shift of the Kuroshio Extension induced the extreme northward meander in 2023.