Snowball Earth climate dynamics and Cryogenian geology-geobiology

• Published in: Science Advances
• Main Authors: Hoffman, Paul F., Abbot, Dorian S., Ashkenazy, Yosef, Benn, Douglas I., Brocks, Jochen J., Cohen, Phoebe A., Cox, Grant M., Creveling, Jessica R., Donnadieu, Yannick, Erwin, Douglas H., Fairchild, Ian J., Ferreira, David, Goodman, Jason C., Halverson, Galen P., Jansen, Malte F., Le Hir, Guillaume, Love, Gordon D., Macdonald, Francis A., Maloof, Adam C., Partin, Camille A., Ramstein, Gilles, Rose, Brian E. J., Rose, Catherine V., Sadler, Peter M., Tziperman, Eli, Voigt, Aiko, Warren, Stephen G.
• Other Authors: Harvard University, University of Chicago, Ben-Gurion University of the Negev (BGU), University of St Andrews Scotland, Australian National University (ANU), Williams College Williamstown, University of South Australia Adelaide, Oregon State University (OSU), Centre Européen de Recherche et d'Enseignement des Géosciences de l'Environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Modélisation du climat (CLIM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Smithsonian Institution, University of Birmingham Birmingham, University of Reading (UOR), Wheaton College Norton, McGill University = Université McGill Montréal, Canada, Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS), University of California Riverside (UC Riverside), University of California (UC), Princeton University, University of Saskatchewan Saskatoon, Canada (U of S), University at Albany SUNY, State University of New York (SUNY), Trinity College Dublin, Institute of Nanotechnology Karlsruhe (INT), Karlsruhe Institute of Technology (KIT), University of Washington Seattle
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2017
• Subjects: [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Ice Sheet
• Online Access: https://hal.science/hal-01765604; https://hal.science/hal-01765604/document; https://hal.science/hal-01765604/file/e1600983.full.pdf; https://doi.org/10.1126/sciadv.1600983

International audience Geological evidence indicates that grounded ice sheets reached sea level at all latitudes during two long-lived Cryogenian (58 and >= 5 My) glaciations. Combined uranium-lead and rhenium-osmium dating suggests that the older (Sturtian) glacial onset and both terminations were globally synchronous. Geochemical data imply that CO$_2$ was 10$^2$ PAL (present atmospheric level) at the younger termination, consistent with a global ice cover. Sturtian glaciation followed breakup of a tropical supercontinent, and its onset coincided with the equatorial emplacement of a large igneous province. Modeling shows that the small thermal inertia of a globally frozen surface reverses the annual mean tropical atmospheric circulation, producing an equatorial desert and net snow and frost accumulation elsewhere. Oceanic ice thickens, forming a sea glacier that flows gravitationally toward the equator, sustained by the hydrologic cycle and by basal freezing and melting. Tropical ice sheets flow faster as CO$_2$ rises but lose mass and become sensitive to orbital changes. Equatorial dust accumulation engenders supraglacial oligotrophic meltwater ecosystems, favorable for cyanobacteria and certain eukaryotes. Meltwater flushing through cracks enables organic burial and submarine deposition of airborne volcanic ash. The subglacial ocean is turbulent and well mixed, in response to geothermal heating and heat loss through the ice cover, increasing with latitude. Terminal carbonate deposits, unique to Cryogenian glaciations, are products of intense weathering and ocean stratification. Whole-ocean warming and collapsing peripheral bulges allow marine coastal flooding to continue long after ice-sheet disappearance. The evolutionary legacy of Snowball Earth is perceptible in fossils and living organisms.