Long-distance migration and venting of methane after marine hydrate dissociation

• Main Authors: Davies, Richard, Yang, Jinxui, Ireland, Mark, Berndt, Christian, Huuse, Mads, Morales-Maqueda, Miguel
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2023
• Subjects: Methane hydrate
• Online Access: https://oceanrep.geomar.de/id/eprint/58196/; https://oceanrep.geomar.de/id/eprint/58196/1/428fff45-8354-4ad3-94ca-82b689836802.pdf; https://oceanrep.geomar.de/id/eprint/58196/2/e31c49d3ece50a11b109d4eb.docx; https://doi.org/10.21203/rs.3.rs-2604587%2Fv1; https://doi.org/10.21203/rs.3.rs-2604587/v1

Marine methane hydrate dissociation has been proposed as a mechanism for past global carbon cycle perturbations and could exacerbate climate change. Modulation of methane venting by bottom water temperature changes has been documented at the landward limit of marine hydrate around continental margins, where vulnerable hydrate exists at or below the seabed. However, in this setting the amount of methane that is climate-sensitive is relatively small as it hosts only ~ 3.5% of the global hydrate reservoir. Here, we show that methane that dissociates from the base of the hydrate stability zone can migrate landward over significant distances from the deepest parts of the continental slope to the shelf break and beyond the landward limit of marine hydrate. We demonstrate this using three-dimensional seismic imaging of the hydrate dissociation zone offshore Mauritania where dissociated methane was channeled at least 40 km and vented through a field of twenty-three giant pockmarks at the shelf break probably during Quaternary interglacials. This shows the ~ 96.5% of methane bound in hydrates further down the slope needs to be considered for estimating climate change-induced methane release during a warming world.