Linking continental slope failures and climate change: Testing the clathrate gun hypothesis
Mark Maslin, University College London, Department of Geography, 26 Bedford Way, London, WC1H 0AP, U.K.; et al. Pages 53-56.
A major debate in science is whether gas hydrate release or changes in tropical wetlands cause the massive variations seen in ice-core atmospheric methane record during the Pleistocene. Because submarine sediment failures can be up to the size of Jamaica, they have the capacity to release vast quantities of methane hydrates. One of the major tests of Jim Kennett's clathrate gun hypothesis is determining whether continental-slope failures and increases in 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. Our data support the clathrate gun hypothesis for glacial-interglacial transitions. The data do not, however, support the clathrate gun hypothesis for the rapid glacial-period millennial-scale climate cycles because the occurrence of sediment failures correlates with the cold Heinrich events. Thus sediment failure correlates with lows in sea level and atmospheric methane. A secondary use of our 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 Bolling-allerod sediment failures are predominantly low latitude, suggesting an early tropical response to deglaciation. 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, again caused by isostatic rebound, causing destabilization of gas hydrates. This correlation implies that the largest threat to continental-slope stability in the possible greenhouse future is melting of the ice-sheet margins and the resultant isostatic rebound. This is a significant worry, as there is already evidence that these processes are occurring in Antarctica and Greenland. Moreover, it should be noted that these continental slope failures would all be accompanied by large tsunamis.
