In this study, we examine the influence of ice dynamics and the sub-grid-scale ice thickness distribution on present-day and climate change simulations in a global coupled ice-ocean-atmosphere model of intermediate complexity. Under present-day conditions the sea-ice physics modifies both the annual mean and seasonal variation of ice-ocean-atmosphere conditions. In models with motionless sea ice, the ice volume increases and undergoes a smaller seasonal cycle. Resolving the ice thickness distribution also increases the ice thickness, but enhances the seasonal cycle. The response of the system to increased atmospheric CO2 forcing is also dependent on the sea ice physics. Simulating ice dynamics and the ice thickness distribution enhances the ice area response. However, the ice volume response is diminished when ice dynamics is included and enhanced when the ice thickness distribution is resolved. The oceanic thermohaline circulation and regional air temperature response to global warming is also dependent on the sea ice parameterizations. Additional simulations were performed to quantify the influence of the albedo feedback mechanism on climate change simulations. When the albedo feedback was inactive, amplified warming was still present (although reduced) at high latitudes due to the poleward retreat of the ice cover and larger ocean-atmosphere heat exchange. In these simulations, the albedo feedback accounted for 17% of the global air temperature increase and over 30% of the Northern Hemisphere ice area and volume decrease. ¿ 2001 American Geophysical Union