Submitted to J. Climate Special Issue on CCSM3

• Main Authors: Frank O. Bryan, Gokhan Danbasoglu, Norikazu Nakashiki Yoshikatsu Yoshida, Scott C. Doney, Woods Hole
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2005
• Subjects: North Atlantic; North atlantic Thermohaline circulation
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.422.1624; http://www.cesm.ucar.edu/publications/jclim04/Papers/OWG4.pdf

The response of the North Atlantic thermohaline circulation to idealized climate forcing of 1 % per year compound increase in CO2 is examined in three configurations of the Community Climate System Model version 3 that differ in their component model resolutions. The strength of the Atlantic overturning circulation declines at a rate of 22% to 26 % of the corresponding control experiment maximum overturning per century in response to the increase in CO2. The mean meridional overturning and its variability on decadal timescales in the control experiments, the rate of decrease in the transient forcing experiments, and the rate of recovery in periods of CO2 stabilization all increase with increasing component model resolution. By examining the changes in ocean surface forcing with increasing CO2 in the framework of the water mass transformation function, we show that the decline in the overturning is driven by decreasing density of the subpolar North Atlantic due to increasing surface heat fluxes. While there is an intensification of the hydrologic cycle in response to increasing CO2, the net effect of changes in surface freshwater fluxes on those density classes that are involved in deep