Capturing the global signature of surface ocean acidification during the PETM

Author(s): Babila, Tali Lea; Penman, Donald E.; Hoenisch, Baerbel; Kelly, Daniel Clay; Bralower, Timothy J.; Rosenthal, Yair; Zachos, James C.
Author Affiliation(s): Primary:
University of California Santa Cruz, Santa Cruz, CA, United States
Other:
Yale University, United States
Lamont-Doherty Earth Observatory, United States
University of Wisconsin Madison, United States
Pennsylvania State University, United States
Rutgers University New Brunswick, United States
Volume Title: AGU 2016 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2016; American Geophysical Union 2016 fall meeting, San Francisco, CA, Dec. 12-16, 2016. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: Anthropogenic greenhouse gas emissions over the last century have elevated atmospheric carbon dioxide concentrations while concomitantly acidifying the oceans. Instrumental records are sparse and limited in duration, making it difficult to separate regional from global trends of ocean acidification. Geologically rapid carbon perturbations such as the Paleocene-Eocene Thermal Maximum (PETM, ∼56 Ma) are arguably the closest paleo analogue to present climate change. Marine ecosystems experienced dynamic changes during the event, and parallel environmental changes, including acidification and warming. Here we present a synthesis of new and published geochemical reconstructions from various oceanographic settings to determine the magnitude and spatial extent of surface ocean acidification. In the deep ocean, acidification is inferred from widespread dissolution of seafloor carbonates, whereas evidence for surface ocean acidification has emerged from planktonic foraminifera boron proxy records (B/Ca and δ11B) (Penman et al. 2014; Babila et al. 2016). B/Ca and δ11B in surface and thermocline planktonic foraminifera suggest a simultaneous decrease at the PETM onset in all pelagic and shelf sites. Salinity, diagenesis and foraminiferal symbiont loss can complicate the interpretation of boron proxy records. Local salinity changes (based on paired Mg/Ca and δ18O) account for a relatively small component of total B/Ca change. The large range in environmental conditions between sites could explain the subtle differences in absolute values exhibited by the records. Shelf sites (ODP 174AX Bass River and Ancora, NJ) reveal similar absolute values and trends compared to pelagic sites (ODP 1209, N. Pacific), precluding a significant preservation bias on the geochemical records. Southern Ocean sites (ODP 689 and 690) are located in colder surface waters and exhibit a similar decrease in B/Ca, suggesting that temperature and symbiont loss are likely not major factors. We conclude that while the mass of released carbon is comparable to anthropogenic emissions, the rate is much slower, resulting in a less severe degree of undersaturation. Furthermore, the consistent latitudinal pattern of acidification suggests that thermal stress rather than acidification contributed to the observed biotic responses.
Year of Publication: 2016
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Acidification; Atlantic Coastal Plain; Cenozoic; Continental shelf; Leg 174AX; Lithostratigraphy; New Jersey; Ocean Drilling Program; Paleocene-Eocene Thermal Maximum; Paleogene; Tertiary; United States
Coordinates: N383000 N402800 W0740000 W0753500
Record ID: 2018006120
Copyright Information: GeoRef, Copyright 2018 American Geosciences Institute. Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union, Washington, DC, United States