Ice Sheet Evolution and Deglaciation Chronology of Southwestern Spitsbergen Illuminated by Three-Nuclide Surface-Exposure Dating (26Al, 10Be, and 14C).

Abstract:

Glacial-interglacial ice-sheet mass changes represent arguably the greatest observable changes in Arctic hydroclimate, yet the rate and timing of even the relatively recent the post-Last Glacial Maximum (LGM) deglaciation remain controversial, casting uncertainty onto predictions of future ice-sheet contributions to sea-level rise. Here we present terrestrial cosmogenic nuclide (TCN) surface-exposure dates that constrain the long-term thickness, erosivity, and late-glacial recession chronology of parts of the western margin of the Svalbard-Barents-Sea Ice Sheet.

Our sampling sites are coastal hills that generally lack glacially transported erratic clasts but commonly feature ice-molded bedrock. Polar ice sheets often fail to remove inventories of long-lived radionuclides built up during prior interglacials, and indeed our ²⁶Al and ¹⁰Be (half-life = 0.7 and 1.4 Ma) data show elevation-dependant concentration differences that are consistent with variable ice cover that was commonly more extensive than at present, but less than during the LGM. All sites that we sampled in the area were ice-covered at the LGM. By measuring ¹⁴C (half-life = 5730 years) in the same samples we can detect the rate of post-LGM ice-sheet thinning. Preliminary data are consistent with marine sediment core dates that show rapid ice-sheet retreat at around 15,000 years ago.