Large equatorial seasonal cycle during Marinoan snowball Earth
© 2020 The Authors. In the equatorial regions on Earth today, the seasonal cycle of the monthly mean surface air temperature is <10°C. However, deep (>1 m) sand wedges were found near the paleoequator in the Marinoan glaciogenic deposits at ∼635 million years ago, indicating a large seasonal cycle (probably >30°C). Through numerical simulations, we show that the equatorial seasonal cycle could reach >30°C at various continental locations if the oceans are completely frozen over, as would have been the case for a snowball Earth, or could reach ∼20°C if the oceans are not completely frozen over, as would have been the case for a waterbelt Earth. These values are obtained at the maximum eccentricity of the Earth orbit, i.e., 0.0679, and will be approximately 10°C smaller if the present-day eccentricity is used. For these seasonal cycles, theoretical calculations show that the deep sand wedges form readily in a snowball Earth while hardly form in a waterbelt Earth.
Publication Source (Journal or Book title)
Liu, Y., Yang, J., Bao, H., Bao, H., Shen, B., & Hu, Y. (2020). Large equatorial seasonal cycle during Marinoan snowball Earth. Science Advances, 6 (23) https://doi.org/10.1126/sciadv.aay2471