Different Trends in Antarctic Temperature and Atmospheric CO2 During the Last Glacial. Issue 14 (23rd July 2021)

• Record Type: Journal Article
• Authors: Zheng, Peisong; Pedro, Joel B.; Jochum, Markus; Rasmussen, Sune O.; Lai, Zhongping
• Is Part Of: Geophysical research letters. Volume 48:Issue 14(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-07-23
• Subjects: Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2021GL093868
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: We analyze the past 67, 000 years of climate using Antarctic ice‐core records to constrain the mechanisms involved in (a) the "bipolar seesaw" relationship between Greenland and Antarctic surface temperature variations, and (b) mechanisms of millennial‐scale atmospheric CO2 concentration variations. Specifically, we determine for each Greenland Stadial the rate of Antarctic temperature and atmospheric CO2 rise. We find that Antarctic warming rates significantly decrease as the climate cools during the glacial period, whereas the rate of atmospheric CO2 rise does not significantly change. Also, we find that the rates of Antarctic warming and atmospheric CO2 rise are both insensitive to whether a given stadial contains a Heinrich event. These results challenge the view that a single Southern‐Ocean‐based mechanism dominates the observed glacial variability in Antarctic temperature and atmospheric CO2 . Instead, our results are consistent with an important contribution of low‐ and mid‐latitude processes to millennial‐scale atmospheric CO2 changes. Plain Language Summary: Glacial climate is characterized by millennial‐scale variations in polar temperature and atmospheric CO2 concentration. The observed similarities between the shape of atmospheric CO2 and Antarctic temperature records, derived from Antarctic ice cores, have led to a common view that variations in both are dominated by a common Southern Ocean mechanism. However, a systematic comparison of the rates of change of Antarctic temperature and atmospheric CO2 during these millennia‐scale events has not previously been conducted. Furthermore, it is not clearly demonstrated if the rate of change of the Antarctic temperature and atmospheric CO2 were sensitive to changes in the mean climate state or the occurrence of massive iceberg discharge into the North Atlantic. Here, using ice‐core data, we show that the rate of Antarctic warming reduces as the glacial climate cools. In contrast, the rate of atmospheric CO2 rise is insensitive to glacial cooling. Neither the warming rate nor the rate of atmospheric CO2 rise are affected by iceberg discharge events. Our result is in contrast with a simple common Southern Ocean control on atmospheric CO2 and Antarctic temperature and suggests that the millennial‐scale atmospheric CO2 changes include significant contributions from mid‐to‐low latitudes and processes independent of the background climate. Key Points: The Antarctic warming rate during Antarctic Isotope Maxima significantly decreased as the climate cooled toward the glacial maximum In contrast, the rate of millennial‐scale CO2 rise is insensitive to the varying background climate The Antarctic warming rate and the rate of millennial‐scale CO2 rise were insensitive to whether the stadial contained a Heinrich event