Purdue University Graduate School

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posted on 2023-04-29, 00:40 authored by Alexandria KoesterAlexandria Koester


Reconstructing past glacier and ice-sheet extents is important to better understand how glacial systems have responded to past climate changes in hope of constraining predictions of their responses to ongoing anthropogenic climate warming. As such, the most recent period of climatic variations, from the Last Glacial Maximum (LGM, ca. 21 ka) through today, is of great interest as a prominent example of how ice has reacted to past climatic warming events. Surface exposure dating utilizing cosmogenic nuclides can directly constrain when past ice deglaciated in current and former glacial landscapes. Numerous studies have utilized long-lived cosmogenic radionuclides (i.e., 10Be, 26Al) in polar regions to reconstruct glacial systems. However, due to prevalent non-erosive cold-based ice, prior nuclides from pre-LGM can be preserved. 

The research described in this dissertation applies in situ cosmogenic 14C (in situ 14C), an emerging geochronometer, to polar glacial landscapes in Sweden and Antarctica to constrain the timing and rate of glacial ice retreat. In situ 14C more closely reflects the post-LGM deglacial signal in polar regions because it is less likely to preserve prior nuclides (inheritance) under minimally erosive ice. Our cosmogenic 10Be–26Al–14C concentrations near the Riukojietna ice cap, the last remaining ice cap in Sweden, combined with a sedimentary record from a proximal proglacial lake, indicate the ice cap likely survived during a warm period in the Holocene, but was less extensive than today. The in situ 14C exposure data from nunataks in western Dronning Maud Land (DML), East Antarctica indicate significant coastal thickening (up to 850 m) not predicted by models to date. In addition, this work dates the timing of post-LGM ice surface lowering in two drainage basins in western DML. These results demonstrate the significant contribution of in situ 14C in polar regions.

In addition to applications of in situ 14C in polar regions, this work also describes the development of a compositionally dependent in situ 14C production rate calculator. The ability to extract in situ 14C from samples which quartz cannot be separated (either quartz-poor or fine-grained) would allow new avenues of research. The computational framework will be a useful tool in efforts to broaden the utility of in situ 14C to quartz-poor and fine-grained rock types. 


Degree Type

  • Doctor of Philosophy


  • Earth, Atmospheric and Planetary Sciences

Campus location

  • West Lafayette

Advisor/Supervisor/Committee Chair

Darryl Granger

Advisor/Supervisor/Committee co-chair

Nathaniel Lifton

Additional Committee Member 2

Marc Caffee

Additional Committee Member 3

Marissa Tremblay

Additional Committee Member 4

Arjen Stroeven

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