The SP19 chronology for the South Pole Ice Core – Part 2: gas chronology, Δage, and smoothing of atmospheric records

A new ice core drilled at the South Pole provides a 54 000-year paleoenvironmental record including the composition of the past atmosphere. This paper describes the SP19 chronology for the South Pole atmospheric gas record and complements a previous paper (Winski et al., 2019) describing the SP19 ic...

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Bibliographic Details
Published in:Climate of the Past
Main Authors: Epifanio, Jenna A., Brook, Edward J., Buizert, Christo, Edwards, Jon S., Sowers, Todd A., Kahle, Emma C., Severinghaus, Jeffrey P., Steig, Eric J., Winski, Dominic A., Osterberg, Erich C., Fudge, Tyler J., Aydin, Murat, Hood, Ekaterina, Kalk, Michael, Kreutz, Karl J., Ferris, David G., Kennedy, Joshua A.
Format: Article in Journal/Newspaper
Language:English
Published: Copernicus Publications 2020
Subjects:
article
Verlagsveröffentlichung
Antarc*
Antarctic
ice core
Ice Sheet
South pole
Online Access:https://doi.org/10.5194/cp-16-2431-2020
https://noa.gwlb.de/receive/cop_mods_00054887
https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00054538/cp-16-2431-2020.pdf
https://cp.copernicus.org/articles/16/2431/2020/cp-16-2431-2020.pdf
Description
Summary:A new ice core drilled at the South Pole provides a 54 000-year paleoenvironmental record including the composition of the past atmosphere. This paper describes the SP19 chronology for the South Pole atmospheric gas record and complements a previous paper (Winski et al., 2019) describing the SP19 ice chronology. The gas chronology is based on a discrete methane (CH4) record with 20- to 190-year resolution. To construct the gas timescale, abrupt changes in atmospheric CH4 during the glacial period and centennial CH4 variability during the Holocene were used to synchronize the South Pole gas record with analogous data from the West Antarctic Ice Sheet Divide ice core. Stratigraphic matching based on visual optimization was verified using an automated matching algorithm. The South Pole ice core recovers all expected changes in CH4 based on previous records. Gas transport in the firn results in smoothing of the atmospheric gas record with a smoothing function spectral width that ranges from 30 to 78 years, equal to 3 % of the gas-age–ice-age difference, or Δage. The new gas chronology, in combination with the existing ice age scale from Winski et al. (2019), allows a model-independent reconstruction of the gas-age–ice-age difference through the whole record, which will be useful for testing firn densification models.

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