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Centennial-scale changes in the global carbon cycle during the last deglaciation
Marcott, Shaun A.,Bauska, Thomas K.,Buizert, Christo,Steig, Eric J.,Rosen, Julia L.,Cuffey, Kurt M.,Fudge, T. J.,Severinghaus, Jeffery P.,Ahn, Jinho,Kalk, Michael L.,McConnell, Joseph R.,Sowers, Todd Nature Publishing Group, a division of Macmillan P 2014 Nature Vol.514 No.7524
Global climate and the concentration of atmospheric carbon dioxide (CO<SUB>2</SUB>) are correlated over recent glacial cycles. The combination of processes responsible for a rise in atmospheric CO<SUB>2</SUB> at the last glacial termination (23,000 to 9,000 years ago), however, remains uncertain. Establishing the timing and rate of CO<SUB>2</SUB> changes in the past provides critical insight into the mechanisms that influence the carbon cycle and helps put present and future anthropogenic emissions in context. Here we present CO<SUB>2</SUB> and methane (CH<SUB>4</SUB>) records of the last deglaciation from a new high-accumulation West Antarctic ice core with unprecedented temporal resolution and precise chronology. We show that although low-frequency CO<SUB>2</SUB> variations parallel changes in Antarctic temperature, abrupt CO<SUB>2</SUB> changes occur that have a clear relationship with abrupt climate changes in the Northern Hemisphere. A significant proportion of the direct radiative forcing associated with the rise in atmospheric CO<SUB>2</SUB> occurred in three sudden steps, each of 10 to 15 parts per million. Every step took place in less than two centuries and was followed by no notable change in atmospheric CO<SUB>2</SUB> for about 1,000 to 1,500 years. Slow, millennial-scale ventilation of Southern Ocean CO<SUB>2</SUB>-rich, deep-ocean water masses is thought to have been fundamental to the rise in atmospheric CO<SUB>2</SUB> associated with the glacial termination, given the strong covariance of CO<SUB>2</SUB> levels and Antarctic temperatures. Our data establish a contribution from an abrupt, centennial-scale mode of CO<SUB>2</SUB> variability that is not directly related to Antarctic temperature. We suggest that processes operating on centennial timescales, probably involving the Atlantic meridional overturning circulation, seem to be influencing global carbon-cycle dynamics and are at present not widely considered in Earth system models.
Giyoon Lee,Jinho Ahn,Hyeontae Ju,Florian Rittrbusch,Ikumi Oyabu,Songyi Kim,Jangil Moon,Christo Buizert,Sambit Ghosh,Kenji Kawamura,Zheng-Tian Lu,Sangbum Hong,Chang Hee Han,Soon Do Hur,Wei Jiang,Guo-Mi 대한지질학회 2021 대한지질학회 학술대회 Vol.2021 No.10
Using ice cores, researchers can obtain multiple records for paleoclimate. However, ice cores from deep drilling projects recover limited amount of ice, prohibiting the paleoclimate studies that need a large amount of ice such as analyzing isotopes of trace gases and metal elements in the ice. Because glaciers outcropped at the surface in blue ice areas (BIAs) allow collection of extensive amount of samples, the BIAs serve as an alternative to the conventional deep ice core drilling sites. However, most of the ice stratigraphy in BIAs is disturbed due to the complicated ice flow, which hinders to figure out the chronostratigraphy of the ice. Here, we report a simple chronostratigraphy of ice from Larsen BIA, Antarctica. Based on dust bands on the surface of the ice and ground penetration radar (GPR) survey, the chronostratigraphy of the studied Larsen BIA shows a monotonic increase of ages in the mid- to downstream side ice. The δ<SUP>18</SUP>Oatm and δ<SUP>2</SUP>Hice values of Larsen ice show a very typical range of the last glacial termination. Correlation of δ<SUP>18</SUP>Oice, δ<SUP>18</SUP>Oatm, and CH₄ records of Larsen ice with existing ice core records indicates that the gas and ice ages ranges are 9.2–23.4 and 5.6–24.7 ka BP, respectively. In addition, radiometric <SUP>81</SUP>Kr dating confirms the constrained ages within analytical uncertainty. Our study may contribute to future research of the paleoclimate during the last glacial termination via the Larsen ice.