Physical Sciences Division
Published November 8, 2017 | Version v1
Journal article Open

Snowball Earth climate dynamics and Cryogenian geology-geobiology

Creators

  • 1. Harvard University
  • 2. University of Chicago
  • 3. Ben-Gurion University of the Negev
  • 4. University of St Andrews
  • 5. Australian National University
  • 6. Williams College
  • 7. University of Adelaide
  • 8. Oregon State University
  • 9. Université Paris-Saclay
  • 10. Smithsonian Institution
  • 11. University of Birmingham
  • 12. University of Reading
  • 13. Wheaton College
  • 14. McGill University
  • 15. Institut de Physique du Globe de Paris
  • 16. University of California, Riverside
  • 17. Princeton University
  • 18. University of Saskatchewan
  • 19. University at Albany
  • 20. Trinity College Dublin
  • 21. Columbia University
  • 22. University of Washington

Description

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 CO2 was 102 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 CO2 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.

Data availability

All data needed to evaluate the conclusions in the paper are present in the paper and/or references cited. Additional data related to this paper may be requested from the authors.

Files

sciadv.1600983.pdf

Files (7.3 MB)

Name Size Download all
Article
md5:65e0d45891bee9348b96f587657e4cf0
7.3 MB Preview Download

Additional details

Identifiers

DOI
10.1126/sciadv.1600983
Other
oai:uchicago.tind.io:10994

Funding

National Science Foundation
AGS-1455071
National Science Foundation
ANT-1142963
BMBF
ECLIPSE
FONAU
01LK1509A

UChicago Information

Division(s)
Physical Sciences Division
Department(s)
Geophysical Sciences