Retarded deglaciation of north-Spitsbergen fjords during the last glacial – an example of bathymetric controls on the dynamics of retreating glaciers

• Main Authors: Forwick, Matthias, Vorren, Tore O., Hass, H. Christian, Vogt, Christoph
• Format: Conference Object
• Language: unknown
• Published: Geophysical Research Abstracts 2012
• Subjects: Svalbard; Austin; Billefjorden; Lomonosovfonna; Wijdefjorden; Austfjorden; Austfjord*; glacier; Wijdefjord*; Spitsbergen
• Online Access: https://epic.awi.de/id/eprint/32136/; https://hdl.handle.net/10013/epic.40785

North and west Spitsbergen fjords acted as pathways for fast-flowing ice streams during the last glacial (e.g. Ottesen et al., 2005). The deglaciation of west Spitsbergen fjords occurred stepwise and the ice retreat terminated around 11,200 cal. years BP (calendar years before the present; e.g. Forwick & Vorren, 2009, 2011, and references therein; Baeten et al., 2010). However, the deglaciation dynamics and chronology of north Spitsbergen fjords still remain poorly understood. We present swath-bathymetry, high-resolution seismic data and two sediment cores from the approx. 110 km long, N-S oriented Wijdefjorden-Austfjorden fjord system, the largest fjord system on northern Spitsbergen. The data indicate that – as in the fjords on west Spitsbergen – multiple halts and/or readvances interrupted the retreat of the ice front during the final phase of the last glacial. However, even though the study area and several west Spitsbergen fjords are fed by the same glacier source (the ice field Lomonosovfonna), the final deglaciation of Wijdefjorden-Austfjorden took place after 9300 cal. years BP, i.e. at least approx. 2000 years later than in the west. We assume that the retarded deglaciation in the north is mainly related to the fjord bathymetry, i.e. a more than 35 km wide and up to 60 m high area in the central parts of the study area (approx. 45 km beyond the present fjord head) that acted as pinning point for the grounded glacier. Multiple, relatively large and partly stacked moraine ridges and sediment wedges are suggested to reflected that the ice front retreated slowly across this shallow area and that repeated readvances interrupted this retreat. The absence of larger sediment wedges in the deeper parts between the shallow area and the fjord head may indicate that the final retreat occurred relatively rapid. References: Baeten, N.J., Forwick, M., Vogt, C. & Vorren, T.O., 2010. Late Weichselian and Holocene sedimentary environments and glacial activity in Billefjorden, Svalbard. In: Howe, J.A., Austin, ...