Investigating the Deglacial History of a Swedish Ice Cap Using Combined In Situ 14C-10Be-26Al

Glaciers in Sweden are retreating and likely to disappear in the coming centuries due to ongoing warming. Therefore, they may have behaved similarly during the warmest periods of the Holocene. Landforms common to many deglacial landscapes are proglacial lakes formed in bedrock basins or impounded by moraines. Although paleoclimate records from proglacial lacustrine sediments are valuable indicators of glacial histories (e.g., Rosqvist et al., 2004), surface exposure dating using in situ cosmogenic nuclides has provided key additional constraints. These exposure dates often span longer time periods particularly in polar regions characterized by cold-based, non-erosive glacial ice (e.g., Schweinsberg et al., 2018; Graham et al., 2019). Riukojietna, the last remaining ice cap in Sweden, is drained by a series of proglacial lakes, and provides an attractive target for such a study. Sediment cores from one of these lakes document Holocene fluctuations in sediment production from this ice cap. We are complementing these records by studying recently exposed bedrock surfaces immediately adjacent to the ice cap, as well as from bedrock surfaces exposed along the lake and immediately below the outlet glacier feeding them. Five bedrock samples from these sites have been analyzed for in situ 14C, 10Be, and 26Al, to investigate potential deglacial ice-cover and exposure histories at Riukojietna. These results will be analyzed in concert with existing local and regional lacustrine and other paleoclimate records, with implications for deglaciation of northern Fennoscandia. Graham, B.L. et al, 2019, New in situ 14C data indicate the absence of nunataks in west Greenland during the Last Glacial Maximum: Quaternary Science Reviews, v. 225, p. 105981, doi:10.1016/j.quascirev.2019.105981. Rosqvist, G. et al., 2004, Diatom oxygen isotopes in pro-glacial lake sediments from northern Sweden: a 5000 year record of atmospheric circulation. Quaternary Science Reviews, v. 23, p. 851859, doi: 10.1016/j.quascirev.2003.06.009. Schweinsberg, A.D. et al., 2018, Holocene mountain glacier history in the Sukkertoppen Iskappe area, southwest Greenland: Quaternary Science Reviews, v. 197, p. 142161, doi:10.1016/j.quascirev.2018.06.014.