Pure rotational Raman spectroscopy applied to N2/O2 analysis of air bubbles in polar firn

• Published in: Journal of Glaciology
• Main Authors: Hiroshi Ohno, Yoshinori Iizuka, Shuji Fujita
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press 2021
• Subjects: Antarctic glaciology; ice core; polar firn; Environmental sciences; GE1-350; Meteorology. Climatology; QC851-999; Antarctic; Antarc*; Journal of Glaciology
• Online Access: https://doi.org/10.1017/jog.2021.40; https://doaj.org/article/93db4de55a49455f8cc77bc0ad52ff4a

Earlier gas measurements of firn air (atmosphere in open pore channels) at polar sites have revealed the occurrence of gas fractionation phenomena during bubble close-off, in addition to well-known thermal and gravitational gas separation. Nevertheless, because of difficulties posed by measurement, little is known about the distribution of air constituents in already closed pores (bubbles) in firn. Herein, we describe the application of high-sensitivity pure rotational Raman spectroscopy, combined with sample immersion in the fluorocarbon-based inert fluid for removing the optical disturbance by diffused reflection. That application efficiently elicits information about nitrogen and oxygen composition ratios (N2/O2 or O2/N2) for each air bubble in firn. The developed methodology presents important implications for elucidating how gas records are formed and modified in the course of pore close-off in polar firn.