Ice sheet and terrestrial input impacts on the 100-kyr ocean carbon cycle during the Middle Miocene

• Published in: Global and Planetary Change
• Main Authors: Ma, Xiaolin, Ma, Wentao, Tian, Jun, Yu, Jimin, Huang, Enqing
• Format: Report
• Language: English
• Published: ELSEVIER 2022
• Subjects: Middle Miocene; Oxygen and carbon isotopes; Carbon cycle; Antarctic ice sheet; Terrestrial inputs; EAST EQUATORIAL PACIFIC; ATMOSPHERIC CO2; CLIMATE; RECORD; DELTA-C-13; CHEMISTRY; EVOLUTION; ATLANTIC; DIOXIDE; TEMPERATURE; Physical Geography; Geology; Geography; Physical; Geosciences; Multidisciplinary; Antarctic; The Antarctic; Pacific; Antarc*; Ice Sheet
• Online Access: http://ir.ieecas.cn/handle/361006/17362; http://ir.ieecas.cn/handle/361006/17363; https://doi.org/10.1016/j.gloplacha.2021.103723

The Middle Miocene (similar to 16-11.6 Ma) had atmospheric CO2 levels comparable to the present day, and thus the mechanisms controlling the interactions of the climate system and the carbon cycle during the Middle Miocene may have significant implications for future climate change. In this study, we examined the phase relationship between benthic foraminiferal delta O-18 and delta C-13 records, within the 100-kyr band, during the Late Quaternary and the Middle Miocene. Our results suggest that benthic foraminiferal delta O-18 and delta C-13 were highly coherent and inphase within the 100-kyr band during the Middle Miocene, in contrast to the anti-phased relationship during the Late Quaternary. However, the causes of this contrast remain elusive. We used a biogeochemical box model to explore the mechanisms of the in-phase relationship in the 100-kyr band during the Middle Miocene. The model results show that the in-phase relationship can be attributed to two mechanisms: (1) a shelf-basin carbonate shift regulated by sea-level fluctuations which originated from the growth and decay of the Antarctic ice sheet, within the 100-kyr band; and (2) changes in terrestrial carbon inputs and the biological pump driven by the discharge of riverine nutrients, which was regulated by precipitation variability in low latitudes, within the eccentricity-modulated precessional band. Thus, we propose that both high- and low-latitude processes played critical roles in the Middle Miocene carbon cycle, within the 100-kyr band. We further show that chemical weathering played a potential role in regulating the atmospheric pCO(2) on the orbital time scale during the Middle Miocene.