Global warming and ocean stratification: A potential result of large extraterrestrial impacts

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.

Asteroid impact, not volcanism, caused the end-Cretaceous dinosaur extinction

“…Although we focus on a more likely terrestrial asteroid impact (18), it has been suggested that a deep ocean impact that does not reach the bathymetric surface could result in a substantial injection of water vapor into the stratosphere. It has been proposed that in such a scenario increased oceanic-derived stratospheric water vapor may have cancelled out any aerosol cooling effect and led to significant surface warming (70). Future studies should focus on investigating the effect of other abiotic drivers (e.g., acidification, halogens, significant surface warming, ultraviolet radiation, fire, carbon cycle disruption) of both asteroid impact and Deccan volcanism, as this may offer another avenue to understand the relative effect of both events.…”

“…The radiative impact of sulfate aerosols is simulated through absorbing and scattering incoming solar radiation across a spectral range of 0.2 to 10 µm assuming a constant aerosol size distribution ( 85 ). A stratospheric residence time of ∼6 y for the sulfate aerosol was implemented taking into account the longer hypothesized residence time of Pierazzo et al ( 20 ) due to increased atmospheric stratification ( 21 , 22 ) as a result of concurrent surface cooling and stratospheric warming ( 70 ). Stratospheric injection of aerosols into the model was initialized at year 40 into the 200-y simulation.…”

Enhanced magnetization of the Marlboro Clay as a product of soil pyrogenesis at the Paleocene–Eocene boundary?

“…Expanded marine sections across the carbon isotope excursion (CIE) and the associated Paleocene-Eocene thermal maximum (PETM), manifestations of a massive perturbation of the global carbon cycle that were first identified in deep-sea sediments at ODP Site 690 (Kennett and Stott, 1991) and soon observed in continental sediments in Wyoming (Koch et al, 1992) (see review by McInerney and Wing, 2011), are preserved on the continental margin of Eastern North America (Cramer et al, 1999;Gibson et al, 1993) and helped inspire the current phase of the New Jersey Coastal Plain Drilling Project (Miller et al, 1997). High-* Corresponding author.…”

CAPRAM reduction towards an operational multiphase halogen and DMS chemistry treatment in the chemistry transport model COSMO-MUSCAT(5.04e)

“…The chemical systems of halogens and DMS interact with each other strongly and are highly influenced by multiphase chemistry (Barnes et al, 2006;Hoffmann et al, 2016;von Glasow and Crutzen, 2004). As oceans cover around 70 % of the Earth's surface (Joshi et al, 2017;Law et al, 2013) and are in strong interaction with densely populated coastal areas (Kummu et al, 2016;von Glasow et al, 2013), this ocean-related atmospheric chemical subsystem is important for both Earth's climate and air quality.…”