Large‐scale simulation of methane hydrate dissociation along the West Spitsbergen Margin

Abstract

[1] Vast quantities of methane are trapped in oceanic hydrate deposits, and there is concern that a rise in the ocean temperature will induce dissociation of these hydrate accumulations, potentially releasing large amounts of methane into the atmosphere. The recent discovery of active methane gas venting along the landward limit of the gas hydrate stability zone (GHSZ) on the shallow continental slope west of Spitsbergen could be an indication of this process, if the source of the methane can be confidently attributed to dissociating hydrates. In the first large-scale simulation study of its kind, we simulate shallow hydrate dissociation in conditions representative of the West Spitsbergen margin to test the hypothesis that the observed gas release originated from hydrates. The simulation results are consistent with this hypothesis, and are in remarkable agreement with the recently published observations. They show that shallow, low-saturation hydrate deposits, when subjected to temperature increases at the seafloor, can release significant quantities of methane, and that the releases will be localized near the landward limit of the top of the GHSZ. These results indicate the possibility that hydrate dissociation and methane release may be both a consequence and a cause of climate change.

Fluxes and fate of dissolved methane released at the seafloor at the landward limit of the gas hydrate stability zone offshore western Svalbard

“…The presence of hydrate reduces sediment permeability such that subsurface gas flow can be directed along the base of the hydrate layer, with seepage at the seafloor in waters shallower than the landward limit of the hydrate stability zone [Naudts et al, 2006;Schmale et al, 2011]. Destabilization of methane hydrate in seafloor sediments is proposed to have contributed to previous episodes of major climate change, including the Paleocene-Eocene thermal maximum [e.g., Dickens, 2011], and recently discovered methane emissions from the seafloor offshore western Svalbard may, at least in part, be related to hydrate dissociation linked to warming of bottom waters [Berndt et al, 2014;Biastoch et al, 2011;Reagan and Moridis, 2009;Thatcher et al, 2013;Westbrook et al, 2009].…”

A transfer function for the prediction of gas hydrate inventories in marine sediments

“…They have attracted increasing interest in marine geosciences for various reasons: (i) the use of GH as additional energy source (e.g. Bohannon, 2008;Hester and Brewer, 2009), (ii) the climate effect of melting GH and CH 4 -release into sea water and the atmosphere induced by seafloor warming (e.g Dickens et al, 1995;Kennett et al, 2003;Milkov, 2004;Reagan and Moridis, 2009), and (iii) the potential of dissociating GH triggering slope failure events (Xu and Germanovich, 2006).…”

Methane Gas Hydrate Stability Models on Continental Shelves in Response to Glacio-Eustatic Sea Level Variations: Examples from Canadian Oceanic Margins

“…Like some previous work [10] our model study is focused primarily on the history of the gas hydrate stability zone and its changes in response to climatic cycles both in the past and the future where they may be influenced by anthropogenic effects. Unlike other previous work [16,17] our model permits only that we infer the maximum potential volumes of methane sequestered or released from gas hydrates in response to climate cycles, based on the changes in the thickness of the gas hydrate stability zone. Our models illustrate effectively the variable history of the gas hydrate stability zone in response to variations in water depth and sea floor temperatures that are themselves influenced by ocean currents.…”

“…These models investigate the effects of rising ocean water temperatures on future marine gas hydrate stability with the intention of characterizing the future conditions under which methane release and climate-forcing feedback might occur. In contrast our models herein, which are more sophisticated than [10] but less so than [16,17], calculate the history of three marine gas hydrate settings on Canadian continental margins of the Atlantic and Pacific oceans during the last ~3.0 Myrs, with a focus on their history since ~14 kyrs and projected ~11.5 kyrs into the future when the current interglacial cyclic is inferred to end. Like some previous work [10] our model study is focused primarily on the history of the gas hydrate stability zone and its changes in response to climatic cycles both in the past and the future where they may be influenced by anthropogenic effects.…”

“…Several studies have employed a variety of models to infer the future response of marine GH's to anticipated future climate including a general warming that results in an increase of sea bottom temperature, both generally [9,16] or regionally, at a variety of scales [10,17,18]. These models investigate the effects of rising ocean water temperatures on future marine gas hydrate stability with the intention of characterizing the future conditions under which methane release and climate-forcing feedback might occur.…”