Modeling long-term climatic effects of impacts: First results

Catastrophic impacts of asteroids or comets on Earth are events that have occurred in the past and will happen in the future. While climate perturbations induced by an impact-generated dust cloud have been studied in recent years, the studies have been restricted to the first year following the event. The aim of this study is to assess the long-term response of the climate including ocean circulation following the impact of a 5-km-diameter asteroid. We modeled the dust evolution, calculated radiation transfer through dust layers, and used a zonally averaged, coupled ocean-atmosphere model to obtain the climatic response. Within less than one year, mean sea surface temperatures (SST) dropped by similar to2 degreesC. Even though most of the dust had been removed from the atmosphere after several months, SST deviations remained larger than 0.1 degreesC for a period of 20 yr following impact. In the first year, ocean temperatures below 500 in depth did not change. Although 60 yr later the main temperature deviations were still located above 1000 in depth, temperature changes occurred throughout the ocean. After 2000 yr the oceans showed slightly increased temperatures. A zone below the surface of the northern Atlantic exhibited increased temperatures by 3 degreesC. Precipitations decreased within months to about half of normal, but recovered after 1 yr. We did not observe glaciation effects.