I/Ca evidence for upper ocean deoxygenation during the PETM. (21st October 2014)

• Record Type: Journal Article
• Authors: Zhou, Xiaoli; Thomas, Ellen; Rickaby, Rosalind E. M.; Winguth, Arne M. E.; Lu, Zunli
• Is Part Of: Paleoceanography. Volume 29:Number 10(2014)
• Page Start: 964
• Page End: 975
• Publication Date: 2014-10-21
• Subjects: I/Ca -- PETM -- foraminifera -- ocean deoxygenation; Paleoceanography -- Periodicals; 551.46
• DOI: 10.1002/2014PA002702
• Languages: English
• ISSNs: 0883-8305

Abstract

Abstract: Anthropogenic global warming affects marine ecosystems in complex ways, and declining ocean oxygenation is a growing concern. Forecasting the geographical and bathymetric extent, rate, and intensity of future deoxygenation and its effects on oceanic biota, however, remains highly challenging because of the complex feedbacks in the Earth‐ocean biota system. Information on past global warming events such as the Paleocene‐Eocene Thermal Maximum (PETM, ~55.5 Ma), a potential analog for present and future global warming, may help in such forecasting. Documenting past ocean deoxygenation, however, is hampered by the lack of sensitive proxies for past oceanic oxygen levels throughout the water column. As yet no evidence has been presented for pervasive deoxygenation in the upper water column through expansion of oxygen minimum zones (OMZs). We apply a novel proxy for paleoredox conditions, the iodine to calcium ratio (I/Ca) in bulk coarse fraction sediment and planktonic foraminiferal tests from pelagic sites in different oceans, and compared our reconstruction with modeled oxygen levels. The reconstructed iodate gradients indicate that deoxygenation occurred in the upper water column in the Atlantic, Indian Oceans, and possibly the Pacific Ocean, as well during the PETM, due to vertical and potentially lateral expansion of OMZs. Key Points: Foraminiferal I/Ca may be a useful paleoceanographic proxy Our I/Ca records demonstrate that OMZs expanded during the PETM