models from collaborating institutions: the ice dynamics of the elastic-viscous-plastic model of Hunke and Dukowicz (Los Alamos CICE model, 1997)with the thermodynamics and ice thickness distribution model from the University of Washington( Bitz 2000; and Bitz and Lipscomb, 1999). The PCTM ice model contains the same physics as the 2001 version of the NCAR CCSM sea ice component, although the two models have different adaptations for time-sequence in coupling to the other components and for separate execution on parallel processors The ice thermodynamics have been completely replaced from what was in PCM-1(see description) to a mass-conserving I-D thermodynamics of Bitz and Lipscomb(1999),(ii) four vertical layes bn o more complete thermodynamic treatment. The ice thermodynamics include: (i)the energy-an vertical temperature gradients in the ice, and(iii) temperature and salinity-dependent thermal properties for ea ice derived from a fixed salinity profile. The model also calculates a ice-state-dependent ice thickness distribution based on the treatment of Bitz et al. (1999). Thickness distribution calculations will normally use 5 thickness categories where separate thermodynamic calculations determine, for each category, quantities such as average albedo, rates of ice growth or melt, vertical heat exchange at the surface, and transmission of solar radiation to the ocean The ice dynamics use the Hunke(2001) updated version of the elastic-viscouS-plastic(EVP) rheology to solve the ice momentum equation, which balance the forces on the ice: wind stress, ocean currents, Coriolis force, gravitational tilt of the ocean surface, inertia, and internal stress of the ice pack. The ice pack resists compression and shear stress, and divergence under shear, and follows the elliptical yield curve of the Hibler(1979)model. The EVP approach is an explicit solution of the ice stress tensor, as opposed to the implicit iterative solution of the Hibler or more recent Hibler and Zhang(1997)model. The EVp solution velocities compare very closely to those of the Hibler and Zhang model, with a considerable improvement in the parallel performance The Hunke and Dukowicz ice model is written in general orthogonal coordinates, so it runs on the same dipole grid as the ocean component(POP). This provides a resolution of ranging between 25 km and 60 km over much of the Arctic, and resolves not only the Fram Strait and Bering Strait but also much of the Canadian archipelago Early results of ice simulation from the PCTM are shown in the papers linked below(PDF format) Weatherly, J W, and C. M. Bitz, 2001: Natural and Anthropogenic Climate Change in the Arctic. 12th Symposium on Global Change and Climate Variations, AMS Weatherly, J. W, C. M. Bitz, and E. C. Hunke, 2001: Parallel Climate Model Simulations with a Dynamic-Thermodynamic Ice Thickness Distribution Model. Sixth Conference on Polar Meteorology and Oceanography, American Meteorol. Soc., Boston(submitted) River Transport Component The river transport model (rTM) was developed by Marcia Branstetter and Jay Famiglietti, researchers at the University of Texas, Austin, based on the work of Vorosmarty et al. (1989)and Miller et al. (1994) This river routing scheme uses the atmospheric T42 grid. The RTM takes into account river flow mass and2 models from collaborating institutions: the ice dynamics of the elastic-viscous-plastic model of Hunke and Dukowicz (Los Alamos CICE model, 1997) with the thermodynamics and ice thickness distribution model from the University of Washington (Bitz 2000; and Bitz and Lipscomb, 1999). The PCTM ice model contains the same physics as the 2001 version of the NCAR CCSM sea ice component, although the two models have different adaptations for time-sequence in coupling to the other components and for separate execution on parallel processors. The ice thermodynamics have been completely replaced from what was in PCM-1 (see description) to a more complete thermodynamic treatment. The ice thermodynamics include: (i) the energy- and mass-conserving 1-D thermodynamics of Bitz and Lipscomb (1999), (ii) four vertical layers to resolve vertical temperature gradients in the ice, and (iii) temperature and salinity-dependent thermal properties for sea ice derived from a fixed salinity profile. The model also calculates a ice-state-dependent ice thickness distribution based on the treatment of Bitz et al. (1999). Thickness distribution calculations will normally use 5 thickness categories where separate thermodynamic calculations determine, for each category, quantities such as average albedo, rates of ice growth or melt, vertical heat exchange at the surface, and transmission of solar radiation to the ocean. The ice dynamics use the Hunke (2001) updated version of the elastic-viscous-plastic (EVP) rheology to solve the ice momentum equation, which balance the forces on the ice: wind stress, ocean currents, Coriolis force, gravitational tilt of the ocean surface, inertia, and internal stress of the ice pack. The ice pack resists compression and shear stress, and divergence under shear, and follows the elliptical yield curve of the Hibler (1979) model. The EVP approach is an explicit solution of the ice stress tensor, as opposed to the implicit iterative solution of the Hibler or more recent Hibler and Zhang (1997) model. The EVP solution velocities compare very closely to those of the Hibler and Zhang model, with a considerable improvement in the parallel performance. The Hunke and Dukowicz ice model is written in general orthogonal coordinates, so it runs on the same dipole grid as the ocean component (POP). This provides a resolution of ranging between 25 km and 60 km over much of the Arctic, and resolves not only the Fram Strait and Bering Strait, but also much of the Canadian Archipelago. Early results of ice simulation from the PCTM are shown in the papers linked below (PDF format): Weatherly, J.W., and C. M. Bitz, 2001: Natural and Anthropogenic Climate Change in the Arctic. 12th Symposium on Global Change and Climate Variations, AMS. Weatherly, J. W., C. M. Bitz, and E. C. Hunke, 2001: Parallel Climate Model Simulations with a Dynamic-Thermodynamic Ice Thickness Distribution Model. Sixth Conference on Polar Meteorology and Oceanography, American Meteorol. Soc., Boston. (submitted). River Transport Component The river transport model (RTM) was developed by Marcia Branstetter and Jay Famiglietti, researchers at the University of Texas, Austin, based on the work of Vörösmarty et.al. (1989) and Miller et.al. (1994). This river routing scheme uses the atmospheric T42 grid. The RTM takes into account river flow mass and