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The evolution of methane vents that pierce the hydrate stability zone in the world's oceans
Author(s) -
Smith Andrew J.,
Flemings Peter B.,
Liu Xiaoli,
Darnell Kristopher
Publication year - 2014
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1002/2013jb010686
Subject(s) - clathrate hydrate , seafloor spreading , methane , geology , salinity , hydrate , chimney (locomotive) , seabed , front (military) , oceanography , petrology , chemistry , inlet , organic chemistry
We present a one‐dimensional model that couples the thermodynamics of hydrate solidification with multiphase flow to illuminate how gas vents pierce the hydrate stability zone in the world's oceans. During the propagation phase, a free‐gas/hydrate reaction front propagates toward the seafloor, elevating salinity and temperature to three‐phase (gas, liquid, and hydrate) equilibrium. After the reaction front breaches the seafloor, the temperature gradient in the gas chimney dissipates to background values, and salinity increases to maintain three‐phase equilibrium. Ultimately, a steady state is reached in which hydrate formation occurs just below the seabed at a rate necessary to replace salt loss. We show that at the Ursa vent in the Gulf of Mexico, the observed salinity and temperature gradients can be simulated as a steady state system with an upward flow of water equal to 9.5 mm yr −1 and a gas flux no less than 1.3 kg m −2 yr −1 . Many of the world's gas vents may record this steady state behavior, which is characterized by elevated temperatures and high salinities near the seafloor.