Tidal modulation and temporal dynamics of methane emissions at the Formosa Ridge: insights from in-situ observations

Methane emissions from cold seeps play an important role in oceanic carbon cycling and climate regulation, yet their temporal dynamics and controlling mechanisms remain poorly understood. We conducted long-term in situ monitoring at the Formosa Ridge (Site F), southwest of Taiwan, using a self-developed ocean observation platform that integrates an acoustic Doppler current profiler (ADCP), conductivity–temperature–depth (CTD) sensors, current meters, and other instruments, enabling multi-parameter correlation analysis. The observations revealed pronounced temporal variability in gas emissions, with emission intensity closely correlated with bottom pressure fluctuations controlled by tidal cycles. The results suggest that hydrostatic pressure changes promote or inhibit hydraulic fracturing, thereby modulating gas release. These findings support a conceptual model of the seep’s fluid system, characterized by a constant subsurface methane supply and tidally modulated episodic bubble discharge, a mechanism likely applicable to other cold seep environments globally and offering new insights into the dynamics of marine methane emissions.