IS METHANE-DRIVEN DEGLACIATION CONSISTENT WITH THE ICE CORE RECORD

The rapid climate changes at the terminations marking the end of the l ast glaciation are poorly understood. This study uses the Cambridge tw o-dimensional atmospheric model to investigate the impact of a large m arine sediment slump or permafrost rupture releasing 4000 Tg of CH4 in to the high latitudes of the northern hemisphere, with particular emph asis on the evolution of atmospheric CH4 concentrations. which may hav e led to an associated direct radiative effect of the order of 1 W m(- 2), persisting for a few decades, because of enhanced levels of atmosp heric CH4. The model-generated CH4 concentrations were converted into synthetic ice core signals for 66 degrees N and 85 degrees S, represen ting Arctic and Antarctic cores, respectively. A range of possible ave raging times was considered. The results show that irrespective of the site or enclosure time chosen, with the current sampling interval of similar to 300 years, it is not possible to discount completely the ex istence of a spike as a result of the instantaneous release of 4000 Tg of CH4. Detection or refutation of a CH4 spike would, however, be pro bable if the sampling interval were reduced to around 50-100 years.