title: Severity of ocean acidification following the end-Cretaceous asteroid impact.
abstract: Most paleo-episodes of ocean acidification (OA) were either too slow or too small to be instructive in predicting near-future impacts. The end-Cretaceous event (66 Mya) is intriguing in this regard, both because of its rapid onset and also because many pelagic calcifying species (including 100% of ammonites and more than 90% of calcareous nannoplankton and foraminifera) went extinct at this time. Here we evaluate whether extinction-level OA could feasibly have been produced by the asteroid impact. Carbon cycle box models were used to estimate OA consequences of (i) vaporization of up to 60 × 10(15) mol of sulfur from gypsum rocks at the point of impact; (ii) generation of up to 5 × 10(15) mol of NOx by the impact pressure wave and other sources; (iii) release of up to 6,500 Pg C as CO2 from vaporization of carbonate rocks, wildfires, and soil carbon decay; and (iv) ocean overturn bringing high-CO2 water to the surface. We find that the acidification produced by most processes is too weak to explain calcifier extinctions. Sulfuric acid additions could have made the surface ocean extremely undersaturated (Ωcalcite <0.5), but only if they reached the ocean very rapidly (over a few days) and if the quantity added was at the top end of literature estimates. We therefore conclude that severe ocean acidification might have been, but most likely was not, responsible for the great extinctions of planktonic calcifiers and ammonites at the end of the Cretaceous.
authors.affiliation: Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Southampton SO14 3ZH, United Kingdom; tt@noc.soton.ac.uk.
authors.forename: Toby
authors.initials: T
authors.lastname: Tyrrell
authors.affiliation: Systems Ecology, Leibniz Center for Tropical Marine Ecology, 28359 Bremen, Germany; and Jacobs University, 28759 Bremen, Germany.
authors.forename: Agostino
authors.identifier: http://orcid.org/0000-0001-8095-8056
authors.initials: A
authors.lastname: Merico
authors.affiliation: Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Southampton SO14 3ZH, United Kingdom;
authors.forename: David Ian
authors.initials: DI
authors.lastname: Armstrong McKay
mesh_terms: D000336:Aerosols; D000818:Animals; D001272:Atmosphere; D002119:Calcium Carbonate / Q000378:metabolism; D057486:Carbon Cycle; D002245:Carbon Dioxide; D053476:Extinction, Biological; D006863:Hydrogen-Ion Concentration; D018543:Minor Planets; D008954:Models, Biological; D008956:Models, Chemical; D009589:Nitrogen Oxides; D009792:Oceans and Seas; D010163:Paleontology; D012623:Seawater / Q000737:chemistry*; D013464:Sulfuric Acids
chemical_list: D000336:Aerosols; D009589:Nitrogen Oxides; D013464:Sulfuric Acids; D002245:Carbon Dioxide; D002119:Calcium Carbonate; C033158:sulfuric acid
keywords: K/Pg boundary; asteroid impact; mass extinction; ocean acidification