Graduation Year
2025
Document Type
Thesis
Degree
M.S.
Degree Name
Master of Science (M.S.)
Degree Granting Department
Marine Science
Major Professor
Brad E. Rosenheim, Ph.D.
Committee Member
Don P. Chambers, Ph.D.
Committee Member
Alastair G.C. Graham, Ph.D.
Keywords
Antarctic Peninsula, El Niño Southern Oscillation, Firn, Ice sheet
Abstract
The Antarctic Peninsula (AP) is one of the foremost indicators of anthropogenic global warming as it interacts with both atmospheric and oceanic processes. Although ice shelves across the AP have undergone increased rates of disintegration over the last 30 years, limited in-situ measurements have been investigated. Assessment of three short (~30 m) firn cores (J108, J208, and J409) across the Larsen C ice shelf (LCIS) provide insight into local, regional, and global processes. Average core densities and isotopic variability (δ¹⁸O and δ²H) fall within expected ranges for all cores, indicating signal preservation through firn. However, isotopic maxima in J108 and J409 show enriched isotopic compositions unusual for both coastal and interior Antarctica. The greatest isotopic outlier is within J409 with a δ¹⁸O value of +5.5‰. Revised peak picking methodology is implemented to reconstruct core time series from δ¹⁸O variability without the need for chronomarkers. Reconstructed time series indicate cores J108, J208, and J409 are all approximately 30 years long. Core densities and isotopes indicate melt layers within cores J108 and J409, but not within J208. Additionally, melt layers and isotopic peaks do not align between cores, indicating local melt variability. Accumulation ranges between 520.0- and 659.4-mm water equivalent (mm w.eq.) per year, with annual accumulation varying between cores. Linear regressions are implemented to investigate the global influence of climate indices (El Niño Southern Oscillation and Southern Annular Mode) on LCIS cores. Even with lag accounted for, <5% of the variability seen within LCIS core time series can be explained by global climate indices alone. Time series Fast Fourier Transforms show that low frequency prominent signals occur within all cores and explain the most variability seen within LCIS firn cores. From these findings, we conclude that LCIS isotopic variability is predominately determined by local processes that vary across the ice shelf. Thus, the contribution of global climate processes is likely overestimated in the LCIS. Further research is required to identify what these local processes are and how they impact internal stability and preservation of large ice shelves.
Scholar Commons Citation
Schomber, Orion Laurene, "What controls ice shelf isotopic variability? Local and global processes preserved within ice cores across the Larsen C Ice Shelf, Antarctica" (2025). USF Tampa Graduate Theses and Dissertations.
https://digitalcommons.usf.edu/etd/11066
