Climate variations in Britain during the last Glacial-Holocene transition (15.0-11.5 cal ka BP): Comparison with the GRIP ice-core record

Stratigraphic records from four sequences in Britain that span the Last Glacial-Holocene transition (c. 15.0-11.5 cal ka BP) are summarized and compared using a calibrated timescale. Palaeoclimatic changes are defined using temperature estimates based on coleopteran data at two of the sites, and chironomid assemblages at the other sites. An attempt is made to distingish between the timing of (a) climate shifts and (b) ecosystem responses at all four sites. The British data are compared with the GRIP ice-core record, recently advocated by Bjorck et al. as the type-sequence for the Last Termination in the North Atlantic region. There is a degree of compatibility between the British and GRIP palaeoclimatic records. The clearest climatic signals in the British lake records are (a) a period of warm conditions (a thermal maximum) between 15.0 and 14.5 cal ka BP, which equates approximately with GRIP zone GI-le; (b) the onset of climatic cooling, which appears to have commenced during GRIP zone GI-le, at c. 14.5 cal ka BP; (c) a period of marked climatic instability from 14.4 to 12.7 cal ka BP, the regional effects of which are difficult to resolve using the evidence presently available; (d) further climatic cooling, which commenced at around 13.0 cal ka BP, after which the lake biota, catchment soils and vegetation cover, at least in some parts of Britain, did not recover until the onset of the Holocene; (e) continued climatic cooling, with the most severe impact on lake ecosystems occurring during the period c. 12.6 to 11.5 cal ka BP.