PP032-0008
Regional Patterns and Temporal Evolution of Ocean Iron Fertilization and CO2 Drawdown during the Last Glacial Termination

Friday, 11 December 2020
Poster
Fabrice Lambert, Pontifical Catholic University of Chile, Geography Institute, Santiago, Chile, Natalia Estefania Opazo, Pontifical Catholic University of Chile, Santiago, Chile, Andy Ridgwell, University of California Riverside, Department of Earth and Planetary Sciences, Riverside, CA, United States, Gisela Winckler, Columbia University, Department of Earth and Environmental Sciences, New York, NY, United States, Frank Lamy, AWI Bremerhaven, Bremerhaven, Germany, Gary Shaffer, Niels Bohr Institute - University of Copenhagen, Copenhagen, Denmark, Karen Elizabeth Kohfeld, Simon Fraser University, School of Resource and Environmental Management and School of Environmental Science, Burnaby, BC, Canada, Rumi Ohgaito, JAMSTEC Japan Agency for Marine-Earth Science and Technology, Kanagawa, Japan, Samuel Albani, Cornell University, Ithaca, NY, United States and Ayako Abe-Ouchi, University of Tokyo, Atmosphere and Ocean Research Institute, Bunkyo-ku, Japan
Abstract:
The last time Earth’s climate experienced geologically rapid global warming was associated with the last glacial termination, when atmospheric pCO2 concentrations rose from 180 ppmv during the Last Glacial Maximum (LGM, 26-19 kaBP) to ~260 ppmv by the early Holocene (12-8 kaBP). About one quarter of that difference is thought to be due to a stronger biological pump during glacial times, driven by increased aeolian dust deposition and hence greater iron availability in ocean surface waters. However, dust supply did not change uniformly or in synchrony over the deglacial transition and what is not known is the relative importance of different oceanic regions and how this may have changed in time. Using an Earth system model of intermediate complexity, we quantify the sensitivity of atmospheric CO2 to regional changes in iron supply, and test six different global dust reconstructions in order to explore uncertainty in past dust changes. We confirm the Southern Ocean (>34°S) as the region most sensitive to iron fertilization, with the Atlantic and Pacific sectors accounting for about 41 ± 23 % and 16 ± 10 %, respectively, of the total CO2 reduction from global iron fertilization. However, the North Pacific contributes 28 ± 3 % to the total implying an important role for Northern Hemisphere processes in driving deglacial CO2 rise. In addition, our analysis reveals an unexpected regional-temporal disparity, and while Southern Hemisphere iron fertilization influences atmospheric pCO2 relatively constantly throughout the termination the impact of the Northern Hemisphere only occurs during the later stages of the termination.
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