ASYNCHRONOUS BEHAVIOUR OF THE LAST FENNOSCANDIAN ICE SHEET

Reconstructions of the Last Glacial Maximum (LGM) show a huge confluent Eurasian ice sheet (Svendsen et al. 2004). Already at the time of this publication, we knew that the maximum position was time-transgressive, but only recently we have been able to explore this in more detail. This presentation will focus on the growth and decay of the Fennoscandian ice sheet and its confluence with the British ice sheet.

The available dates reveal an old (29 – 25 ka) maximum position in the western, maritime areas, and a comparable young (20 – 16 ka) maximum position in the eastern, continental areas (Vorren & Plassen 2002; Demidov et al. 2006; Larsen et al. 2006; Sejrup et al. 2009; Clark et al. 2010; Kalm 2012; Marks 2012). A time – distance diagram across the ice sheet covering this entire time span show western rapidly advancing and retreating ice fronts as opposed to a steadily growing and decaying eastern counterpart. One consequence is that the ice sheet never looked as we normally portray it (Svendsen et al. 2004), and time-slice reconstructions, although crude, show considerable detail in the pattern of growth and decay. Even if the maximum frontal positions were highly asynchronous and seemingly out of phase with global ice volumes, volumetric reconstructions of the Eurasian ice sheet had its maximum at about 21 ka BP, i.e. in phase with the global maximum.

The causes behind the observed variability are complex. Factors like asymmetry in terms of ice-growth nuclei areas, the continental shelf edge being a topographic barrier to further growth, maritime versus continental climate, and west - east differences in topography and bed conditions will be discussed. The relative importance of these to the inferred dynamic variability remains enigmatic.