Linking continental-slope failures and climate change: Testing the clathrate gun hypothesis

Abstract

It has been suggested that the release of clathrates rather than expansion of wetlands is the primary cause of the rapid increases observed in the ice-core atmospheric methane record during the Pleistocene. Because submarine sediment failures can involve as much as 5000 Gt of sediment and have the capacity to release vast quantities of methane hydrates, one of the major tests of the clathrate gun hypothesis is determining whether the periods of enhanced continental-slope failure and atmospheric methane correlate. To test the clathrate gun hypothesis, we have collated published dates for submarine sediment failures in the North Atlantic sector and correlated them with climatic change for the past 45 k.y. More than 70% by volume of continental-slope failures during the past 45 k.y. was displaced in two periods, between 15 and 13 ka and between 11 and 8 ka. Both these intervals correlate with rising sea level and peaks in the methane record during the Bølling-Å llerød and Preboreal periods. These data support the clathrate gun hypothesis for glacial-interglacial transitions. The data do not, however, support the clathrate gun hypothesis for glacial millennial-scale climate cycles, because the occurrence of sediment failures correlates with Heinrich events, i.e., lows in sea level and atmospheric methane. A secondary use of this data set is the insight into the possible cause of continental-slope failures. Glacial-period slope failures occur mainly in the low latitudes and are associated with lowering sea level. This finding suggests that reduced hydrostatic pressure and the associated destabilization of gas hydrates may be the primary cause. The Bølling-Å llerød sediment failures were predominantly low latitude, suggesting an early tropical response to deglaciation, e.g., enhanced precipitation and sediment load to the continental shelf or warming of intermediate waters. In contrast, sediment failures during the Preboreal period and the majority of the Holocene occurred in the high latitudes, suggesting either isostatic rebound-related earthquake activity or reduced hydrostatic pressure caused by isostatic rebound, causing destabilization of gas hydrates.

Timing and frequency of large submarine landslides: implications for understanding triggers and future geohazard

“…The compiled data set of ages of submarine landslides contains 68 large 884 landslides at continental margins worldwide, and is significantly larger than 885 previously published data sets (Maslin et al, 2004;Owen et al, 2007;Lee, 2009;886 Leynaud et al, 2009). For further interpretation of the data set it is important 887 to recall that for a large part of the data base uncertainty in ages is significant,…”

“…Does land-82 slide frequency vary significantly with sea level, or could the pattern of landslide 83 ages be random and unrelated to sea level? We apply basic statistics to the data 84 set and assess whether the impact of sea level cycles on landslide timing is as 85 strong as previously suggested (Maslin et al, 2004;Owen et al, 2007;Lee, 2009). …”

Tsunamis: bridging science, engineering and society

“…It is likely that the impact of meteotsunamis will change. In terms of landslides, while back in 2004 it was asserted that, based on volume, 70% of slope failures in continental margins in the last 45 000 years occurred in periods of rapid sea-level rise [125], more recent analysis suggests that the evidence is inconclusive [126]. It is however possible that a warming ocean may trigger methane releases from the seafloor though gas hydrate dissociation; Urlaub et al [126] argued that a bottom water temperature increase of even 1 • C in water depths less than 600 m 'can cause the release of significant amounts of free gas and this can promote slope instability'.…”

First-Order Estimation of In-Place Gas Resources at the Nyegga Gas Hydrate Prospect, Norwegian Sea

“…Upon entering the Norwegian-Greenland Sea through the Faroe-Shetland inflow, the NAC is partially branched as the south-easterly flowing Norwegian Channel Inflow. In addition, the Norwegian Coastal Current (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) • C, Klitgaard-Kristensen et al [45]) flows along the Norwegian coast, being strongly controlled by seasonal variation. A large publicly available data set [46] Location of the Nyegga study area, offshore mid-Norway.…”