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【1.4】学术报告:Drivers and Consequences of the End-Cretaceous Impact Winter
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2019-01-02 | 【 【关闭】
报告人:Clay Tabor
报告人单位:university of Connecticut
报告时间:2019年1月4日下午2:30
报告地点:LAPC多功能厅
    A prolonged global winter was a likely consequence of the Chicxulub impact due to aerosol emissions from the impactor, the impact site, and fires. However, there remain large uncertainties about the magnitude of the impact winter and its contribution to the Cretaceous-Paleogene (K-Pg) mass extinction. Here, we use a complex Earth system model with an explicit aerosol resolving scheme, high-top atmosphere, and Maastrichtian boundary conditions to explore the potential drivers and effects of the end-Cretaceous impact winter. Emissions come from the latest estimates of soot, sulfur, and dust injected into the atmosphere. Although all emissions reduce shortwave radiation at the surface, which results in global cooling, the magnitude and duration of the responses differ significantly. Dust emission instantaneously reduces surface light levels to zero but falls out of the atmosphere in a few months due to rapid particle growth, leading to relatively little global cooling. Sulfur emission has a comparatively long residence time in the stratosphere, which reduces surface light levels for over 5 years and produces a maximum global surface cooling of 15°C. Still, light levels never become low enough to prevent photosynthesis due to the growth of large particles that limit extinction efficiency. In contrast, soot strongly absorbs solar radiation, which causes it to heat and loft into the upper atmosphere. The soot particles reduce surface light levels to below 1% of normal for almost 2 years and cause a 16.5°C drop in global surface temperature. In our simulations, soot produces the greatest radiatively-driven disruption of the three impact winter aerosols and likely helps explain the extensive loss of ocean primary producers across the K-Pg.
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