A new approach to modelling sources of fluorescent organic matter in Antarctic ice cores

Harris, Matthew Richard Pain

Abstract

Organic matter trapped within the earth’s ice sheets holds a wide array of potential paleoenvironmental information but remains under-investigated. The fraction that exhibits intrinsic fluorescence, known as fluorescent organic matter (FOM), is broadly comprised of conjugated, aromatic molecules and offers an attractive combination of inherent simplicity and sensitivity in its detection. Despite the increasing number of analyses targeting organic matter in ice cores, only a handful of studies have attempted to analyse this ‘glowing ice’. This thesis is focused on developing, then applying and evaluating, three-dimensional spectroscopic methods (EEM-PARAFAC) to analyse FOM for its proxy potential in ice cores from Antarctica. Modelled fluorophores were resolved in ice and firn core archive samples from Mill Island and Law Dome (East Antarctica), and Patriot Hills (West Antarctica). Natural and contaminant fluorescent signatures were distinguished by leveraging a novel model validation technique and dedicated characterisations of interferent fluorophores arising from contamination. A new water isotope and ion chemistry record for the Patriot Hills Firn Core is reported alongside a dedicated airmass back-trajectory analysis to characterise the sensitivity of the site and record. Both Patriot Hills and Mill Island resolve a ‘tryptophan-like’ or ‘indole-like’ fluorophore that is identical within the statistical uncertainties inherent to three-dimensional fluorescence modelling. This signature is highly spectrally similar to those reported from a wide range of sea ice environments and in sea spray aerosol, including in regions explicitly identified along atmospheric transport vectors to Patriot Hills. Annual correlations of this fluorophore at Patriot Hills are significantly correlated to sea ice concentrations in the Amundsen-Bellingshausen (positive) and Weddell Seas (negative). This signal is thus tentatively identified as the first evidence of a sea-ice imprint upon preserved FOM in Antarctic ice cores across the satellite era (1979–present).

Citation

Harris, M. R. P. (2024). A new approach to modelling sources of fluorescent organic matter in Antarctic ice cores. (Thesis). Keele University. Retrieved from https://keele-repository.worktribe.com/output/853232

• Thesis Type: Thesis
• Deposit Date: Jun 21, 2024
• Public URL: https://keele-repository.worktribe.com/output/853232
• Additional Information: Embargo on access until 19 June 2027 - The thesis is due for publication, or the author is actively seeking to publish this material.
• Award Date: 2024-06