Seafloor methane emission on the Makran continental margin

Area of Science:

• Marine geology
• Geochemistry
• Environmental science

Background:

• Seafloor methane emission impacts climate, ocean chemistry, and ecosystems.
• Submarine methane seepage detection and quantification are limited by water depth.
• Understanding methane seepage is crucial for assessing environmental impacts.

Purpose of the Study:

• To systematically detect, quantify, and assess the activity of submarine methane seepage on the Makran continental margin.
• To provide new datasets for understanding methane seep behavior in this region.
• To evaluate the environmental impact of methane seepage on the Makran continental margin.

Main Methods:

• Comprehensive geological survey using R/V "Haiyangdizhi 10" in 2018.
• Multibeam mapping, seafloor observation, and seismic reflection profiling.
• Detection and quantification of seafloor methane flares and flux estimation.

Main Results:

• Sixty-five gas flares indicating methane seepage were identified in a 32,000 km² survey area.
• Estimated total methane flux: 4.7-5.9 × 10³ Mg/yr, a small fraction of global emissions.
• Three previously active seeps were inactive in 2018, suggesting intermittent activity.
• All methane flares dissipated in the water column; no atmospheric release observed.

Conclusions:

• Submarine methane seepage is active on the Makran continental margin, but its contribution to global emissions is minor.
• Intermittent seep activity may be linked to subsurface pressure dynamics.
• Methane is primarily oxidized or dissolved in seawater, with no direct atmospheric input detected.
• The study provides valuable data for understanding methane seep behavior and environmental implications.