9/1/2005 Climate Sensitivity of Moderate and Low Resolution Versions of

• Main Authors: Ccsm To Preindustrial Forcings, Bette L. Otto-bliesner, Robert Tomas, Esther C. Brady, Caspar Ammann, Zav Kothavala, Gabriel Clauzet, Dr. Bette Otto-bliesner
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Antarctic; Pacific; The Antarctic; Antarc*; North Atlantic; Sea ice
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.422.3339; http://www.cesm.ucar.edu/publications/jclim04/Papers/PWG2b.pdf

Preindustrial (PI) simulations of CCSM3 at two resolutions, a moderate resolution and a low resolution, are described and compared to the standard controls for present-day (PD). Because of computational efficiency, the moderate and low resolution versions of CCSM3 may be appropriate for climate change studies requiring simulations of the order of hundreds to thousands of years. The PI simulations provide the basis for comparison for proxy records that represent average late Holocene conditions. When forced with preindustrial trace gases, aerosols, and solar irradiance estimates, both resolutions have a global cooling of 1.2-1.3°C, increased sea ice in both hemispheres, and less precipitation near the equator and at mid-latitudes as compared to simulations using present-day forcing. The response to PI forcings differs in the two resolutions for North Atlantic meridional overturning circulation (MOC), the Antarctic Circumpolar Current (ACC), and ENSO. The moderate resolution CCSM3 has enhanced ACC, North Atlantic MOC, and tropical Pacific ENSO variability for PI forcings as compared to PD. The low resolution CCSM3 with more extensive sea ice and colder climate at high northern latitudes in the PD simulation shows less sensitivity of the North Atlantic MOC to PI forcing. ENSO variability and the strength of the ACC do not increase with PI forcing in the low resolution CCSM3. 1