Heat Flux Intensified Coastal Thermal Fronts in the East China Shelf Seas

Oceanic thermal fronts (OTFs) in Large Marine Ecosystems worldwide have generally intensified over the past decade; however, the regional manifestations of these changes and the underlying physical mechanisms remain unclear. Using high-resolution sea surface temperature data from 2003 to 2024 and a mixed-layer heat budget model, we quantified the annual trends of ten quasi-stationary OTFs in the East China shelf seas during winter and diagnosed their thermodynamic controls. Seven coastal fronts have strengthened due to increased air-sea heat loss, primarily driven by latent and sensible heat fluxes. In contrast, three shelf and shelf-break fronts remained stable, owing to compensating warm advection. These contrasting trends are closely linked to climate modes: the intensified East Asian winter monsoon reinforced the coastal fronts, while the westward migration of the Kuroshio axis suppressed surface cooling, maintaining the stability of the shelf and shelf-break fronts. Given the ecological and biogeochemical significance of OTFs, the intensified coastal fronts could further influence spatial patterns of matter exchange and primary production in the ocean.