Water input into the Mariana subduction zone estimated from ocean-bottom seismic data

Area of Science:

• Geophysics
• Earth Science
• Seismology

Background:

• The deep Earth water cycle is poorly understood, with significant uncertainty in water flux estimates at subduction zones.
• Previous seismic studies suggested hydration in subducting plates but lacked depth constraints, especially for older plates.

Purpose of the Study:

• To investigate the extent of mantle hydration beneath the Mariana trench using seismic data.
• To refine estimates of water subduction into the Earth's mantle.

Main Methods:

• Analysis of Rayleigh-wave dispersion from ocean-bottom seismic data.
• Generation of seismic images of the crust and uppermost mantle around the Mariana trench.

Main Results:

• Seismic images reveal mantle hydration extending approximately 24 km beneath the Moho discontinuity.
• Calculated water subduction is at least 4.3 times higher than previous estimates for the region.
• Global water flux estimates into the mantle (>100 km depth) may need to be tripled.

Conclusions:

• Old, cold subducting slabs may carry significantly more water than previously estimated.
• Revised estimates of water subduction impact our understanding of the deep Earth water cycle.
• Upward revision of water expulsion at volcanic arcs and backarc basins is likely necessary.