2001/01/01 by Norman H. Sleep, Kevin Zahnle · 14 citations
Earth and Planetary Sciences · #Paleontology and Stratigraphy of Fossils #Geological and Geochemical Analysis #Geology and Paleoclimatology Research
paper · doi:10.1029/2000je001247
openalex publication_date 2001/01/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/02
The crustal Urey cycle of CO 2 involving silicate weathering and metamorphism acts as a dynamic climate buffer. In this cycle, warmer temperatures speed silicate weathering and carbonate formation, reducing atmospheric CO 2 and thereby inducing global cooling. Over long periods of time, cycling of CO 2 into and out of the mantle also dynamically buffers CO 2 . In the mantle cycle, CO 2 is outgassed at ridge axes and island arcs, while subduction of carbonatized oceanic basalt and pelagic sediments returns CO 2 to the mantle. Negative feedback is provided because the amount of basalt carbonatization depends on CO 2 in seawater and therefore on CO 2 in the air. On the early Earth, processes involving tectonics were more vigorous than at present, and the dynamic mantle buffer dominated over the crustal one. The mantle cycle would have maintained atmospheric and oceanic CO 2 reservoirs at levels where the climate was cold in the Archean unless another greenhouse gas was important. Reaction of CO 2 with impact ejecta and its eventual subduction produce even lower levels of atmospheric CO 2 and small crustal carbonate reservoirs in the Hadean. Despite its name, the Hadean climate would have been freezing unless tempered by other greenhouse gases.