| Summary: | Thesis (M.S.) University of Alaska Fairbanks, 2022 The Arctic is experiencing warming and ecological shifts due to climate change and the compounded effects of polar amplification. There is a deficit of information surrounding the carbon cycle response in Arctic Alaskan coastal marsh environments to these forces. The Cape Espenberg barrier beach system has been mostly preserved through time as a shoreline-parallel, linear geometry prograding geomorphic feature. This study determines the Arctic carbon and mineral accumulation trends in marsh environments at Cape Espenberg for both paleo (pre 1850 AD) and modern (post 1850 AD) timeframes. This project makes connections between the responses of carbon and mineral materials to paleo and modern climate changes, and how this relationship may have evolved through time. Analytical analyses through radioisotope ¹³⁷Cs and ²¹⁰Pb, ¹⁴C, stable isotope spectrometry (δ¹³C), elemental (%C, %N, C:N), and dry bulk density and carbon density measurements yield a comprehensive physical and chemical dataset. Radioisotope dating techniques in the Arctic have proved challenging due to the dynamism of the environment. However, the combination of Constant Rate of Supply and Constant Initial Concentration age depth models has helped constrain ages to sediment cores even under variable conditions. Results indicate carbon and mineral accumulations have increased from paleo to modern times which indicates better growing and/or preservation conditions for organic matter (OM) under a modern climate. This agrees well with paleoclimate trends in the Medieval Climate Anomaly (MCA), and warm periods interspersed within the Little Ice Age (LIA), which correlate to greater productivity of terrestrial organic matter and isotopically lighter δ¹³C values (a terrestrial signature). Cold climate periods within the Little Ice Age correlate with increased aquatic organic matter sourcing and heavier δ¹³C values. Modern warming will likely continue to drive carbon sourcing towards terrestrial signatures ...
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