Seafloor methane emission on the Makran continental margin

Area of Science:

• Marine geology
• Geochemistry
• Environmental science

Background:

• Seafloor methane emission impacts climate, ocean acidification, and carbon cycling.
• Submarine methane seepage detection and quantification are limited by water depth.
• The Makran continental margin is a key area for studying these emissions.

Purpose of the Study:

• To systematically detect and quantify methane seeps on the Makran continental margin.
• To assess the environmental impact of submarine methane seepage in the region.
• To understand the activity patterns and fate of methane released from the seafloor.

Main Methods:

• Comprehensive geological survey using R/V "Haiyangdizhi 10" in 2018.
• Multibeam mapping, seafloor observation, and seismic reflection profiling.
• Detection of 65 gas flares indicating seafloor methane seepage over 32,000 km².

Main Results:

• Estimated total methane flux of 4.7-5.9 × 10³ Mg/yr, representing 0.013-0.016% of global seafloor emissions.
• Observed inactivity of three previously active gas seeps, suggesting intermittent seepage.
• Complete oxidation or dissolution of methane in the water column; no atmospheric release detected.

Conclusions:

• New datasets provide crucial insights into methane seep behavior on the Makran margin.
• Intermittent seep activity may be linked to subsurface pressure dynamics.
• Seafloor methane emissions are largely contained within the marine environment, undergoing biogeochemical transformations.