Global warming and ocean stratification: A potential result of large extraterrestrial impacts. Issue 8 (24th April 2017)

• Record Type: Journal Article
• Authors: Joshi, Manoj; von Glasow, Roland; Smith, Robin S.; Paxton, Charles G. M.; Maycock, Amanda C.; Lunt, Daniel J.; Loptson, Claire; Markwick, Paul
• Is Part Of: Geophysical research letters. Volume 44:Issue 8(2017)
• Page Start: 3841
• Page End: 3848
• Publication Date: 2017-04-24
• Subjects: climate dynamics -- asteroid impact -- meteor impact -- radiative forcing -- K‐Pg boundary -- Neoproterozoic; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2017GL073330
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: The prevailing paradigm for the climatic effects of large asteroid or comet impacts is a reduction in sunlight and significant short‐term cooling caused by atmospheric aerosol loading. Here we show, using global climate model experiments, that the large increases in stratospheric water vapor that can occur upon impact with the ocean cause radiative forcings of over +20 W m −2 in the case of 10 km sized bolides. The result of such a positive forcing is rapid climatic warming, increased upper ocean stratification, and potentially disruption of upper ocean ecosystems. Since two thirds of the world's surface is ocean, we suggest that some bolide impacts may actually warm climate overall. For impacts producing both stratospheric water vapor and aerosol loading, radiative forcing by water vapor can reduce or even cancel out aerosol‐induced cooling, potentially causing 1–2 decades of increased temperatures in both the upper ocean and on the land surface. Such a response, which depends on the ratio of aerosol to water vapor radiative forcing, is distinct from many previous scenarios for the climatic effects of large bolide impacts, which mostly account for cooling from aerosol loading. Finally, we discuss how water vapor forcing from bolide impacts may have contributed to two well‐known phenomena: extinction across the Cretaceous/Paleogene boundary and the deglaciation of the Neoproterozoic snowball Earth. Key Points: Large increases in stratospheric water vapor following large bolide impact events over the ocean cause positive radiative forcings Impact events are capable of warming climate and stratifying upper ocean over 1‐2 decades even after initial surface cooling The process could have significantly reduced or possibly even reversed decadal cooling following Chicxulub impact