The Initiation of Modern "Soft Snowball" and "Hard Snowball" Climates in CCSM3. Part II: Climate Dynamic Feedbacks

• 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: SEA-ICE; HEAT-TRANSPORT; CARBON-CYCLE; DEEP-TIME; EARTH; OCEAN; ATMOSPHERE; ENERGY; CO2; CIRCULATIONS; Antarctic; The Antarctic; Antarc*; North Atlantic Deep Water; North Atlantic; Sea ice
• Online Access: https://hdl.handle.net/20.500.11897/296882; https://doi.org/10.1175/JCLI-D-11-00190.1

This study investigates the climate dynamic feedbacks during a transition from the present climate to the extremely cold climate of a "Snowball Earth" using the Community Climate System Model, version 3 (CCSM3). With the land-sea distribution fixed to modern, it is found that by reducing solar luminosity and/or carbon dioxide concentration: 1) the amount of atmospheric water vapor and its attendant greenhouse effect decrease with the logarithm of sea ice cover, thereby promoting the expansion of sea ice; 2) over the sea ice, the cloud radiative feedback is positive, thus enhancing sea ice advance; over the ocean, the cloud radiative feedback is first negative and then becomes positive as sea ice enters the tropics; and 3) the strength of the atmospheric Hadley cell and the wind-driven ocean circulation increases significantly in the Southern Hemisphere, inhibiting the expansion of sea ice into the tropics. Meanwhile, the North Atlantic Deep Water cell disappears and the Antarctic Bottom Water cell strengthens and expands to occupy almost the entire Atlantic basin. In the experiment with 6% less solar radiation and 70 ppmv CO2 compared to the control experiment with 100% solar radiation and 355 ppmv CO2 near the ice edge (28 degrees S latitude), the changes of solar radiation, CO2 forcing, water vapor greenhouse effect, longwave cloud forcing at the top of the model, and atmospheric and oceanic energy transport are -22.4, -6.2, -54.4, +6.2, and +16.3 W m(-2), respectively. Therefore, the major controlling factors in producing global ice cover are ice albedo feedback (Yang et al., Part I) and water vapor feedback. http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000302787300010&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701 Meteorology & Atmospheric Sciences SCI(E) EI 19 ARTICLE 8 2737-2754 25