Climatically driven instability of marine methane hydrate along a canyon-incised continental margin

Establishing how past climate change affected the stability of marine methane hydrate is important for our understanding of the impact of a future warmer world. As oceans shallow toward continental margins, the base of the hydrate stability zone also shallows, and this delineates the feather edge of marine methane hydrate. It is in these rarely documented settings that the base of the hydrate stability zone intersects the seabed and hydrate can crop out where it is close to being unstable and most susceptible to dissociation due to ocean warming. We show evidence for a seismically defined outcrop zone intersecting canyons on a canyon-incised margin offshore of Mauritania. We propose that climatic, and hence ocean, warming since the Last Glacial Maximum as well as lateral canyon migration, cutting, and filling caused multiple shifts of the hydrate stability field, and therefore hydrate instability and likely methane release into the ocean. This is particularly significant because the outcrop zone is longer on canyon-incised margins than on less bathymetrically complex submarine slopes. We propose considerably more hydrate will dissociate in these settings during future ocean warming, releasing methane into the world's oceans.

Automated summary

Understanding how past climate change impacted the stability of marine methane hydrate is crucial for predicting potential methane release in a warmer future world. By studying the seismically defined outcrop zone offshore of Mauritania, it is shown that climatic warming since the Last Glacial Maximum, combined with lateral canyon migration, cutting, and filling, has caused shifts in the hydrate stability field, leading to potential methane release into the ocean. This suggests that under future ocean warming, significantly more methane may be released into the world's oceans, particularly in canyon-incised margins.