The exchange of moisture and heat between the atmosphere and the Earth's surface fundamentally affect the dynamics and thermodynamics of the climate system. In order to trace moisture flow through the climate system and examine its impact on climate, a hydrologic cycle and a land surface energy balance are incorporated into a coupled climate-thermodynamic sea ice (CCSI) model. The expanded CCSI model is tested by comparing its climate simulations with available observations and GCM modeling results. In general, the expanded model does a good job in simulating the large-scale features of the atmospheric circulation and precipitation in both space and time. The expanded model is used to examine the role of the hydrologic cycle in initiating ice sheet growth in response to changes in atmospheric composition. The results indicate that variations in summer ice melt in response to changes in the land ice albedo, and thus in air temperatures, are more important in determining the initiation of ice sheet growth than variations in precipitation. ¿ American Geophysical Union 1995