Enhanced Chlorophyll Responses to the Interaction Between an Anticyclonic Eddy and Internal Solitary Waves: A Case Study

Mesoscale eddies and internal solitary waves (ISWs) influence upper-ocean chlorophyll variability, yet their roles in the spatial variations in chlorophyll during their interaction remain poorly revealed. Using satellite ocean-color and sunglint imagery, we observed different chlorophyll variabilities in three cases: an ISW-only case, an eddy-only case, and an eddy–ISW interaction case. In the ISW-only case, chlorophyll exhibited coherent, banded, and phase-dependent anomalies, characterized by reduced concentrations near the wave trough but enhanced ones in the trailing region, with a chlorophyll anomaly reaching approximately 0.02 mg m−3. In the eddy-only case, chlorophyll exhibited a distinct low-core but high-periphery structure, with elevated filamentary features concentrated around the eddy boundary and spatially consistent with enhanced finite-size Lyapunov exponent (FSLE). During the eddy–ISW interaction, the ISW crests became strongly deformed near the eddy periphery, consistent with modulation by the mesoscale eddy. Within the eddy interior, the ISW-related banded chlorophyll structure remained evident, whereas near the eddy periphery these bands became curved and spatially overlapped with filamentary chlorophyll structures. The difference in chlorophyll between the eddy–ISW and eddy-only cases increased toward the eddy periphery, reaching approximately 50% at ~1.2R. These observations reveal a multiscale spatial modulation of chlorophyll variability, in which the mesoscale eddy establishes a broader spatial pattern, while ISWs induce propagating fine-scale perturbations. The eddy–ISW interaction primarily regulates and enhances chlorophyll variability near the eddy periphery, rather than producing a uniform response throughout the eddy.