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Temporal evolution of mechanisms controlling ocean carbon uptake during the last glacial cycle

Citation

Kohfeld, KE and Chase, Z, Temporal evolution of mechanisms controlling ocean carbon uptake during the last glacial cycle, Earth and Planetary Science Letters, 472 pp. 206-215. ISSN 0012-821X (2017) [Refereed Article]

Copyright Statement

© 2017 The Author(s).

DOI: doi:10.1016/j.epsl.2017.05.015

Abstract

Many mechanisms have been proposed to explain the ∼85-90 ppm decrease in atmospheric carbon dioxide (CO2) during the last glacial cycle, between 127,000 and 18,000 yrs ago. When taken together, these mechanisms can, in some models, account for the full glacial–interglacial CO2 drawdown. Most proxy-based evaluations focus on the peak of the Last Glacial Maximum, 24,000–18,000 yrs ago, and little has been done to determine the sequential timing of processes affecting CO2 during the last glacial cycle. Here we use a new compilation of sea-surface temperature records together with time-sequenced records of carbon and Nd isotopes, and other proxies to determine when the most commonly proposed mechanisms could have been important for CO2 drawdown. We find that the initial major drawdown of 35 ppm 115,000 yrs ago was most likely a result of Antarctic sea ice expansion. Importantly, changes in deep ocean circulation and mixing did not play a major role until at least 30,000 yrs after the first CO2 drawdown. The second phase of CO2 drawdown occurred ∼70,000 yrs ago and was also coincident with the first significant influences of enhanced ocean productivity due to dust. Finally, minimum concentrations of atmospheric CO2 during the Last Glacial Maximum resulted from the combination of physical and biological factors, including the barrier effect of expanded Southern Ocean sea ice, slower ventilation of the deep sea, and ocean biological feedbacks.

Item Details

Item Type:Refereed Article
Keywords:carbon cycle, ice age, ocean circulation, paleoceanography, glacial–interglacial
Research Division:Earth Sciences
Research Group:Physical Geography and Environmental Geoscience
Research Field:Palaeoclimatology
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Earth Sciences
Author:Chase, Z (Associate Professor Zanna Chase)
ID Code:117418
Year Published:2017
Funding Support:Australian Research Council (FT120100759)
Deposited By:Centre for Oceans and Cryosphere
Deposited On:2017-06-14
Last Modified:2017-07-21
Downloads:0

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