On the role of volcanic CO2 outgassing in the global carbon cycle on orbital time scales: two case studies from the last glacial cycle

• Main Authors: Köhler, Peter, Hasenclever, J., Knorr, Gregor, Ronge, Thomas, Rüpke, L., Tiedemann, Ralf
• Format: Conference Object
• Language: unknown
• Published: 2016
• Subjects: Antarc*; Antarctic
• Online Access: https://epic.awi.de/id/eprint/40315/; https://hdl.handle.net/10013/epic.47390

Increasing evidences point to a more important role of volcanic CO2 outgassing in the carbon cycle than previously thought. Here we present two examples, where data or models indicate that only volcanic CO2 outgassing might explain some observed phenomena. (1) The paleo data show that atmospheric CO2 and Antarctic temperature changes are surprisingly synchronous on both millennial and orbital time scale, although there are some still unexplained exceptions. Here we show that the decoupling of temperature and CO2 around the transition into full glacial conditions around the MIS 5/4 boundary (~75kyr BP) might have been caused by the volcanic CO2 degassing, that itself was triggered by the sea level fall of 60-100m within ~10kyr. An additional volcanic CO2 release from mid ocean ridges and hotspots calculated with a state-of-the- art 3D geodynamical model to ~500 to 900 GtCO2 might explain the bulk of the ~18 ppm CO2 anomaly, that is associated with this decoupling of CO2 and temperature on orbital time scales. (2) Radiocarbon (14C) is widely used to detect the carbon that has been transferred from the atmosphere to the deep ocean during the LGM. New 14C data from a depth transect indicate that this carbon might be found at mid water depths (~3 km) in the South Pacific. However, the maximum observed anomaly in deep ocean Δ14C to the atmosphere of -1000permil can only be explained if a realistic increase in reservoir age and a hydrothermal influx of 14C-free CO2 from mid ocean ridges are considered together.