Climatic and ecological responses to Bennu-type asteroid collisions

There is an estimated chance of 0.037% that asteroid Bennu will collide with Earth in 2182 CE. The potential collision of such medium-sized asteroids can inject massive amounts of dust into the atmosphere, with unknown consequences for terrestrial and marine ecosystems. Here, we use the coupled high-top Community Earth System Model Version 2 with interactive chemistry to investigate how medium-sized asteroid strikes would affect climate, vegetation, and marine productivity. Our simulations, which inject up to 400 million tons of dust into the stratosphere, show marked disruptions in climate, atmospheric chemistry, and global photosynthesis. Global mean temperatures are projected to drop by 4°C, and global precipitation decreases by 15% in our simulations. The largest relative reductions in global terrestrial and marine net primary productivity reach 36 and 25%, respectively. Depending on the iron amount of the asteroid and the subsequent marine dust deposition, large diatom blooms occur in iron-limited regions such as the Southern Ocean and the eastern equatorial Pacific.