Measurement of exceptionally high biospheric productivity at the beginning of MIS11 based on Δ17O of O2 in ice cores
Abstract
During the Quaternary, the deglaciations are associated with large changes of atmospheric CO2 concentration with a difference of up to 100 ppm between the glacial and the interglacial periods. A complete and quantitative explanation for these CO2 increases in atmospheric CO2 concentration is still an open question since several fluxes contribute to the variations of atmospheric CO2. Biological productivity is often invoked as one of the processes involved in the changes of atmospheric CO2, and understanding its impact over deglaciations is key. While marine and continental proxies have been used to reconstruct the past variations of productivity at a regional scale, measurements of Δ17O of O2 (ln(δ17O+1) - 0,516 ln(δ18O+1)) in ice core has revealed to be a good indicator for inferring the past variation of global biospheric oxygen fluxes. We focus here on the special case of Termination V and the influence of the flux associated with biospheric productivity. Of the last 9 deglaciations, Termination V displays a unique feature. This deglaciation occurs during a minimum in eccentricity and follows a strong glacial period (MIS 12) preceding the long and warm MIS 11 interglacial period. It is the first termination clearly associated with the 100 ka glacial - interglacial periodicity after the MPT. Here we present the first record of the variation of the global biospheric productivity reconstructed from the triple isotopic composition of atmospheric oxygen (Δ17O of O2) measured in the bubbles of 50 samples of EDC ice core (Antarctica) over Termination V, i.e. from 444,1 to 405,7 ka. Compared to the previous records of Δ17O of O2 on the last 400 ka (Blunier et al., 2012), results show that Termination V is the only termination on which we can observe a different trend between CO2 and Δ17O of O2, the decrease of Δ17O of O2 during the Termination and the beginning of MIS 11 being twice longer than the increase in CO2. This shift reflects an increase in global oxygen biospheric productivity up to 20 % higher compared the other interglacial periods hence confirming the specificity of Termination V and MIS 11. We then confront this result to other long series linked to terrestrial and marine productivities for a perspective on the link between CO2 concentration and productivity over Termination V compared to the 4 younger Terminations.
- Publication:
-
EGU General Assembly Conference Abstracts
- Pub Date:
- April 2019
- Bibcode:
- 2019EGUGA..21.4139B