Millennial and orbital-scale variability in a 54 000-year record of total air content from the South Pole ice core

The total air content (TAC) of polar ice cores has long been considered a potential proxy for past ice sheet elevation. Recent work, however, has shown that a variety of other factors also influence this parameter. In this paper we present a high-resolution TAC record from the South Pole ice core (S...

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Bibliographic Details
Published in:The Cryosphere
Main Authors: Epifanio, Jenna A., Brook, Edward J., Buizert, Christo, Pettit, Erin C., Edwards, Jon S., Fegyveresi, John M., Sowers, Todd A., Severinghaus, Jeffrey P., Kahle, Emma C.
Format: Article in Journal/Newspaper
Language:English
Published: Copernicus Publications 2023
Subjects:
article
Verlagsveröffentlichung
Greenland
South Pole
Isi
Tac
ice core
Ice Sheet
South pole
The Cryosphere
Online Access:https://doi.org/10.5194/tc-17-4837-2023
https://noa.gwlb.de/receive/cop_mods_00069888
https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00068256/tc-17-4837-2023.pdf
https://tc.copernicus.org/articles/17/4837/2023/tc-17-4837-2023.pdf
Description
Summary:The total air content (TAC) of polar ice cores has long been considered a potential proxy for past ice sheet elevation. Recent work, however, has shown that a variety of other factors also influence this parameter. In this paper we present a high-resolution TAC record from the South Pole ice core (SPC14) covering the last 54 000 years and discuss the implications of the data for interpreting TAC from ice cores. The SPC14 TAC record shows multiple features of interest, including (1) long-term orbital-scale variability, (2) millennial-scale variability in the Holocene and last glacial period, and (3) a period of stability from 35 to 25 ka. The longer, orbital-scale variations in TAC are highly correlated with integrated summer insolation (ISI), corroborating the potential of TAC to provide an independent dating tool via orbital tuning. Large millennial-scale variability in TAC during the last glacial period is positively correlated with past accumulation rate reconstructions as well as δ15N-N2, a firn thickness proxy. These TAC variations are too large to be controlled by direct effects of temperature and too rapid to be tied to elevation changes. We propose that grain size metamorphism near the firn surface explains these changes. We note, however, that at sites with different climate histories than the South Pole, TAC variations may be dominated by other processes. Our observations of millennial-scale variations in TAC show a different relationship with accumulation rate than observed at sites in Greenland.

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