[dinosaur] Rapid ocean acidification and long recovery after K/Pg impact (free pdf)

Ben Creisler
[email protected]

A new paper with free pdf:

Michael J. Henehan, Andy Ridgwell, Ellen Thomas, Shuang Zhang, Laia
Alegret, Daniela N. Schmidt, James W. B. Rae, James D. Witts, Neil H.
Landman, Sarah E. Greene, Brian T. Huber, James R. Super, Noah J.
Planavsky, and Pincelli M. Hull (2019)
Rapid ocean acidification and protracted Earth system recovery followed the
end-Cretaceous Chicxulub impact.
Proceedings of the National Academy of Sciences (advance online publication)
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1073_pnas.1905989116&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=G78eRLaQiZaJCwsdRkb5vvvH6MgXuTvCLUW10amt9Ik&s=qpL7-pPNRSKDbSOPrvVqey9fA1rZOmYt9TzFzeexvPk&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.pnas.org_content_early_2019_10_15_1905989116&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=G78eRLaQiZaJCwsdRkb5vvvH6MgXuTvCLUW10amt9Ik&s=Yo1dQcz5v4_HMi_DCG1d6UrgWqQeELjfdFfpek7UiHk&e= 

Significance

Debate lingers over what caused the last mass extinction 66 million years
ago, with intense volcanism and extraterrestrial impact the most widely
supported hypotheses. However, without empirical evidence for either’s
exact environmental effects, it is difficult to discern which was most
important in driving extinction. It is also unclear why recovery of
biodiversity and carbon cycling in the oceans was so slow after an
apparently sudden extinction event. In this paper, we show (using boron
isotopes and Earth system modeling) that the impact caused rapid ocean
acidification, and that the resulting ecological collapse in the oceans had
long-lasting effects for global carbon cycling and climate. Our data
suggest that impact, not volcanism, was key in driving end-Cretaceous mass
extinction.

Abstract

Mass extinction at the Cretaceous–Paleogene (K-Pg) boundary coincides with
the Chicxulub bolide impact and also falls within the broader time frame of
Deccan trap emplacement. Critically, though, empirical evidence as to how
either of these factors could have driven observed extinction patterns and
carbon cycle perturbations is still lacking. Here, using boron isotopes in
foraminifera, we document a geologically rapid surface-ocean pH drop
following the Chicxulub impact, supporting impact-induced ocean
acidification as a mechanism for ecological collapse in the marine realm.
Subsequently, surface water pH rebounded sharply with the extinction of
marine calcifiers and the associated imbalance in the global carbon cycle.
Our reconstructed water-column pH gradients, combined with Earth system
modeling, indicate that a partial ∼50% reduction in global marine primary
productivity is sufficient to explain observed marine carbon isotope
patterns at the K-Pg, due to the underlying action of the solubility pump.
While primary productivity recovered within a few tens of thousands of
years, inefficiency in carbon export to the deep sea lasted much longer.
This phased recovery scenario reconciles competing hypotheses previously
put forward to explain the K-Pg carbon isotope records, and explains both
spatially variable patterns of change in marine productivity across the
event and a lack of extinction at the deep sea floor. In sum, we provide
insights into the drivers of the last mass extinction, the recovery of
marine carbon cycling in a postextinction world, and the way in which
marine life imprints its isotopic signal onto the geological record.

News:

Mystery solved: Ocean acidity in the last mass extinction

https://urldefense.proofpoint.com/v2/url?u=https-3A__news.yale.edu_2019_10_21_mystery-2Dsolved-2Docean-2Dacidity-2Dlast-2Dmass-2Dextinction&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=G78eRLaQiZaJCwsdRkb5vvvH6MgXuTvCLUW10amt9Ik&s=ZUSh2xLusgz6pi_AeKlGNvMQ_5DsOlUJzJ6fROJgGEc&e= 

https://urldefense.proofpoint.com/v2/url?u=https-3A__phys.org_news_2019-2D10-2Dmystery-2Docean-2Dacidity-2Dmass-2Dextinction.html&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=G78eRLaQiZaJCwsdRkb5vvvH6MgXuTvCLUW10amt9Ik&s=F2gM2XjVMOca7p_8ITpKuIQ3Wi-xLY31qqtr3TZ0Lnc&e= 

It was the asteroid, not volcanoes

https://urldefense.proofpoint.com/v2/url?u=https-3A__cosmosmagazine.com_earth-2Dsciences_it-2Dwas-2Dthe-2Dasteroid-2Dnot-2Dvolcanoes&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=G78eRLaQiZaJCwsdRkb5vvvH6MgXuTvCLUW10amt9Ik&s=3sMDnCEwM8l9Z6v5h69OG8YTtl_SluIXdxDtS7eT7tc&e= 

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