Weichselian history of the Fennoscandian Ice Sheet centre, Kvarken archipelago, western Finland—flow shifts, thermal regime and deglaciation

A rapid collapse of the Fennoscandian Ice Sheet (FIS) occurred during the Early Holocene, triggered by abrupt warming and intense meltwater activity. This study reveals a sequence of six ice-flow stages in the Kvarken archipelago where postglacial uplift exposes well-preserved glacial landforms. Striation data from 700 sites indicate minimal bedrock erosion during stable ice sheet phases (MIS 4 and MIS 3/2), but a <400-year pulse of subglacial activity around 10.7–10.5 ka led to widespread erosion, flow shifts, and the formation of new landforms like megaflutings and drumlins. The ice margin retreated at unprecedented rates (200–1000 m/year), leaving De Geer moraines in deep water before final deglaciation. This case study highlights centennial-scale changes at the ice sheet bed, offering insights into past ice sheet instability and its response to climate shifts.

Putkinen, N., Tervo, T., Hall, A. M., Lunkka, J. P., Sarala, P., Breilin, O., & Nenonen, J. (2026). Weichselian history of the Fennoscandian Ice Sheet centre, Kvarken archipelago, western Finland—flow shifts, thermal regime and deglaciation. Boreas, 55(3), 670–701. Portico. https://doi.org/10.1111/bor.70064