Effects of bottom water warming and sea level rise on Holocene hydrate dissociation and mass wasting along the Norwegian‐Barents Continental Margin

Abstract

1] Gas hydrate (GH) stability modeling results explain why some major Holocene submarine landslides along the Norwegian-Barents margin could have been triggered by GH dissociation during the early to middle Holocene, not during the lowest sea levels of the Last Glacial Maximum (LGM). Our model results show that subbottom depths of 170-260 m below the pre-slide continental slope (ca. 350-475 m present water depth) must have passed out of gas hydrate stability zone (GHSZ) by 8.15 ka as the effect of warm bottom water inflow at 11 ka penetrated into the subbottom, overcoming the effects of pressure increase due to sea level rise (SLR). The component of local SLR due to the isostatic response to Fennoscandian deglaciation is shown to be relatively insignificant, particularly for the part of the upper continental slope where the slide probably began. The stability relations show that GH could have formed under the ice sheet before deglaciation, and below deeper shelf areas after sea levels began to rise, but before significant warming near the GHSZ base. To the extent water deeper than 800 m has remained cold (À1°to 0°C) since LGM times, the GHSZ continued to thicken in deep water and GH dissociation could not have triggered Holocene failure in that regime. The present distribution of GH stability is limited to water depths greater than about 400 m in the Storegga slide area, and the thickness of the GHSZ increases with water depth.Citation: Jung, W.-Y., and P. R. Vogt (2004), Effects of bottom water warming and sea level rise on Holocene hydrate dissociation and mass wasting along the Norwegian-Barents Continental Margin,

Estimation of the global inventory of methane hydrates in marine sediments using transfer functions

“…For simplicity, and following previous works, a value of 1 W m −1 K −1 was used in our calculations (e.g. Wood and Yung, 2008;Reitz et al, 2007;Jung and Vogt, 2004;Wallmann et al, 2012). A density of 1000 kg m −3 for water was considered to estimate the hydrostatic pressure at each grid point.…”

Norwegian margin outer shelf cracking: a consequence of climate-induced gas hydrate dissociation?

“…While the former is assumed to be translated immediately through the interconnected pore spaces, the latter needs time before the stability of in situ hydrates is reached. Induced bottom water temperature effects are supposed to occur instantaneously, with full amplitude, taking place at the transition of the Younger Dryas and the Holocene (Jung and Vogt 2004;Mienert et al 2005). In such case, the situation is reduced to a half-space problem with known (estimated) initial geothermal regime.…”

Controls on the formation and stability of gas hydrate‐related bottom‐simulating reflectors (BSRs): A case study from the west Svalbard continental slope

“…[49] The effect of climatically driven p -T perturbations on the GHSZ have been modeled by, among others, Foucher et al [2002] at the Nankai slope, Jung and Vogt [2004] on the Norwegian margin, Bangs et al [2005] at Hydrate Ridge, and Mienert et al [2005] at the Storegga slide. Here we use the sea level data of Fairbanks [1989] and an estimated bottom water temperature change of +0.4°C at the end of the Y. Dryas [Kristensen et al, 2003;Mienert et al, 2005] to quantify the effect of PleistoceneHolocene deglaciation on the GHSZ west of Svalbard (Appendix B).…”