Understanding Signals of the South Pole Ice Core: Chronology, Climate, and Firn Processes

• Main Author: Epifanio, Jenna A.
• Other Authors: Brook, Edward J., Pettit, Erin, Buizert, Christo, Creveling, Jessica, College of Earth, Ocean, and Atmospheric Sciences
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Oregon State University
• Subjects: Ice cores; Antarctic; South Pole; Tac; Antarc*; Antarctica; ice core; South pole
• Online Access: https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/wd376402d

The South Pole ice core (SPC14), drilled in the field seasons of 2014/2015 and 2015/2016, is an intermediate length, 1,751-m ice core which preserves a 54,000-year record of past climate and atmospheric composition. The SPC14 ice core adds to the spatial grid of ice cores in Antarctica extending into the Last Glacial Period. This dissertation develops a highly resolved methane (CH4) record, gas chronology(SP19), and total air content (TAC) record for the SPC14 ice core. These detailed nature of these records provides valuable insight into climate conditions during the last 54,000 years. The first part of the dissertation describes the generation of an atmospheric CH4 record for the entire length of the SPC14 ice core and use of this record to create a gas age time scale for the core. 10-cm long samples were taken at 1-meter intervals. Those samples were measured using a wet extraction technique at the ice core labs at Oregon State University and Pennsylvania State University. The complete record includes a total of 2,318 measurements at 1,067 individual depths.The CH4 record was then used to create a gas chronology (SP19) for the SPC14 ice core. The gas chronology was created by visually matching rapid CH4 variations to the WAIS Divide (WD) ice core, another well-dated Antarctic ice core, using 52 manually chosen tie points. The chronology was then improved by using an automated optimization algorithm. The independently dated gas age scale, and previously created independently dated ice age scale also allowed the creation of an empirically derived record of the gas age-ice age difference(Δage) the first of its kind for an Antarctic ice core. The high-resolution CH4 record revealed small, centennial-scale variations in CH4 throughout the Holocene. The second part of this thesis examines the nature of these variations in more detail. The CH4 variability corroborates similar variations found in the Late Holocene [Mitchell et al., 2011], the Last Glacial Period [Rhodes et al., 2017], and the Holocene record from the ...