Significant variability in marine hydrate stability

Natural gas hydrate stores hundreds to thousands of gigatons of metastable carbon on Earth in a solid, ice-like clathrate. Hydrate stability is well defined in laboratory measurements, but we argue that fundamental constraints on hydrate stability are not understood in natural systems. In marine seismic data, bottom simulating reflections (BSR) are thought to mark the base of the hydrate stability zone. BSRs usually parallel the seafloor and deepen in the sediment column as water depths increase. Herein, we observe that BSR depths from 70 BSRs across the northern Gulf of Mexico vary over 100 s of meters and do not coincide with the calculated thermodynamic base of methane hydrate stability. BSR depths also do not have a strong correlation with water depth. Moreover, at several locations in deepwater, BSRs approach the seafloor suggesting hydrate here could be at risk of dissociation. Subsurface salt appears to control broad trends in BSR depths in the Gulf of Mexico, but there are still unaccounted processes influencing the stability of hydrate systems. “Bottom simulating reflections (BSR) vary over 100 s of meters and do not coincide with the calculated thermodynamic base of methane hydrate stability, as shown using 70 BSR measurements across the northern Gulf of Mexico.”