The Initiation of Modern "Soft Snowball" and "Hard Snowball" Climates in CCSM3. Part I: The Influences of Solar Luminosity, CO2 Concentration, and the Sea Ice/Snow Albedo Parameterization

The "Snowball Earth" hypothesis, proposed to explain the Neoproterozoic glacial episodes in the period 750-580 million years ago, suggested that the earth was globally covered by ice/snow during these events. This study addresses the problem of the forcings required for the earth to enter...

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Bibliographic Details
Published in:Journal of Climate
Main Authors: Yang, Jun, Peltier, W. Richard, Hu, Yongyun
Other Authors: Yang, J (reprint author), 40 Gerrard St E,Apt 3308, Toronto, ON M5B 2E8, Canada., Univ Toronto, Dept Phys, Toronto, ON, Canada., Peking Univ, Lab Climate & Ocean Atmosphere Studies, Dept Atmospher & Ocean Sci, Sch Phys, Beijing 100871, Peoples R China., 40 Gerrard St E,Apt 3308, Toronto, ON M5B 2E8, Canada.
Format: Journal/Newspaper
Language:English
Published: journal of climate 2012
Subjects:
ICE-THICKNESS DISTRIBUTION
LOW-LATITUDE ICE
ENERGY-BALANCE
TEMPORAL VARIABILITY
EARTH DEGLACIATION
GLOBAL GLACIATION
HEAT-TRANSPORT
OBLIQUITY
FEEDBACK
DYNAMICS
Sea ice
Online Access:https://hdl.handle.net/20.500.11897/296881
https://doi.org/10.1175/JCLI-D-11-00189.1
Description
Summary:The "Snowball Earth" hypothesis, proposed to explain the Neoproterozoic glacial episodes in the period 750-580 million years ago, suggested that the earth was globally covered by ice/snow during these events. This study addresses the problem of the forcings required for the earth to enter such a state of complete glaciation using the Community Climate System Model, version 3 (CCSM3). All of the simulations performed to address this issue employ the geography and topography of the present-day earth and are employed to explore the combination of factors consisting of total solar luminosity, CO2 concentration, and sea ice/snow albedo parameterization that would be required for such an event to occur. The analyses demonstrate that the critical conditions beyond which runaway ice-albedo feedback will lead to global freezing include 1) a 10%-10.5% reduction in solar radiation with preindustrial greenhouse gas concentrations; 2) a 6% reduction in solar radiation with 17.5 ppmv CO2; or 3) 6% less solar radiation and 286 ppmv CO2 if sea ice albedo is equal to or greater than 0.60 with a snow albedo of 0.78, or if sea ice albedo is 0.58 with a snow albedo equal to or greater than 0.80. These bifurcation points are very sensitive to the sea ice and snow albedo parameterizations. Moreover, "soft Snowball" solutions are found in which tropical open water oceans stably coexist with year-round snow-covered low-latitude continents, implying that tropical continental ice sheets would actually be present. The authors conclude that a "soft Snowball" is entirely plausible, in which the global sea ice fraction may reach as high as 76% and sea ice margins may extend to 10 degrees S(N) latitudes. http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000302787300009&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701 Meteorology & Atmospheric Sciences SCI(E) EI 21 ARTICLE 8 2711-2736 25

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