Climate and ocean pH on early Earth

Researchers report estimates of the climate and ocean pH on early Earth. Understanding the origin and early evolution of life requires an understanding of the climate and ocean chemistry of early Earth. However, estimates of surface temperatures on early Earth vary widely, from below 0 °C to above 70 °C, whereas ocean pH estimates vary from acidic to highly alkaline. To provide more physical, rigorous estimates, Joshua Krissansen-Totton and colleagues simulated the geological carbon cycle over the past 4 billion years of Earth's history. The model explicitly couples seafloor weathering to climate and the geological carbon cycle, thereby allowing self-consistent calculations of temperature and ocean pH through time. The model yielded relatively constant temperatures throughout history, with a temperate climate of 0-50 °C during the Archean Eon, 2.5-4 billion years ago. Ocean pH increased steadily and gradually from a mildly acidic value of 6.6 at 4 billion years ago to the modern, mildly basic value of 8.2. Negative feedbacks from continental and seafloor weathering stabilized the temperature and pH against changes in sunlight intensity and volcanic outgassing. The results suggest that life emerged under climatic and pH conditions similar to those on modern Earth, with implications for the possibility of life on Earth-like exoplanets, according to the authors.

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Article #17-21296: "Constraining the climate and ocean pH of the early Earth with a geological carbon cycle model," by Joshua Krissansen-Totton, Giada N. Arney, and David C. Catling.

MEDIA CONTACT: Joshua Krissansen-Totton, University of Washington, Seattle, WA; tel: 206-402-7007; e-mail: joshkt@uw.edu