Wintertime Cross-Correlational Structures Between Sea Surface Temperature Anomaly and Atmospheric-and-Oceanic Fields in the East/Japan Sea Under Arctic Oscillation

The winter Arctic Oscillation (AO) modulates the East Asian climate and the East/Japan Sea (EJS) thermodynamics, yet the local, scale-dependent air–sea couplings remain unclear. Using 30 years of daily fields (1993–2022), we map at each grid point, the cross-persistence and scale-dependent cross-correlations between sea surface temperature anomalies (SSTA) and (i) atmospheric anomalies, (ii) turbulent heat-flux anomalies (sensible and latent), and (iii) oceanic anomalies. Detrended Fluctuation/Cross-Correlation Analyses (DFA/DCCA, 5–50 days) yield the Hurst exponent (H, hXY) and the DCCA coefficient (ρdcca). Significance is assessed with iterative-AAFT surrogates and Benjamini–Hochberg false discovery rate (FDR). Three robust features emerge: (1) during AO+, the East Korean Bay–Subpolar Front corridor shows large SSTA variance and high long-term memory (H≥ 1.5); (2) turbulent heat-flux anomalies are anti-phased with SSTA and show little cross-persistence; (3) among oceanic fields, SSHA and meridional geostrophic velocity provide the most AO-robust positive coupling. Within a fractal frame, DFA slopes (1<H<2) quantify local self-similarity; interpreting winter anomalies as fBm implies a fractal-dimension proxy D=3−H, so AO+ hot spots exhibit D≤1.5. These fractal maps, together with ρdcca, offer a compact way to pre-locate marine-heatwave-prone regions. The grid-point, FDR-controlled DFA/DCCA approach is transferable to other marginal seas.