The glacial history of the British Isles during the Early and Middle Pleistocene : implications for the long-term development of the British Ice Sheet

Abstract

The Early and Middle Pleistocene (ca. 2.6–0.125 Ma) was a period of major climate and earth system change driven by a progressive trend of global cooling. This includes the so-called Middle Pleistocene Transition (MPT) (Head and Gibbard, 2005a) which represents a shift (1.2–0.7 Ma) from global climate forcing driven by 41 ka (obliquity) cycles to a pattern of forcing driven by 100 ka (eccentricity) cyclicity (Clark et al., 2006). The global effects of the MPT on various physical, chemical and biological systems have been documented by a number of papers within Head and Gibbard (2005b). However, one of its most obvious global consequences was to produce longer and more intense ‘cold’ periods, which changed both the long- and short-term development of ice sheets and the timing and scale of glaciation (Ehlers and Gibbard, 2007). A large number of Pleistocene ice sheets, including the Scandinavian (SIS), Laurentide and Greenland ice sheets, plus several smaller maritime ice sheets, lie adjacent to the climatically sensitive North Atlantic region. Recent research has demonstrated that each of these ice sheets underwent a step-wise amplification in both the frequency and scale of glaciation across the MPT ( [Jansen et al., 2000] , [Sejrup et al., 2005] and [Knies et al., 2009] ). However, it remains unclear how the British Ice Sheet (BIS) fits into this regional trend as its long-term development is poorly understood. This is due largely to the fragmentary and sometimes ambiguous nature of the evidence for glaciation in Britain, difficulties with correlating evidence between terrestrial and offshore sequences and major problems regarding chronology and correlation with geological sequences in other countries in northwestern Europe ( [Clark et al., 2004] , [Ehlers and Gibbard, 2004] , [Ehlers and Gibbard, 2007] , [Rose, 2009] and [Lee et al., 2010] ). The scope of this chapter is to examine spatial and temporal patterns in the scale of glaciation within the Early and Middle Pleistocene British Isles. This will provide a greater understanding behind the controls of the long-term development of glaciation in Britain, and whether it was in-phase with global climate change and other Northern Hemisphere Ice Sheets. This has important implications for understanding the sensitivity of the British land-mass and the level of coupling to climate change. Particular focus is placed upon: (1) reviewing and evaluating the evidence for Early and Middle Pleistocene glaciations; (2) identifying long-term trends in the development of glaciation in Britain; (3) drivers of glaciations and their wider context