Description: We present results from a greenhouse warming experiment obtained from an atmosphere-ocean-sea ice general circulation model that is fully interactively coupled with a three-dimensional model of the Greenland ice sheet. The experiment covers the period 1970-2099 and is driven by the IPCC SRES B2 scenario. The Greenland model is a thermomechanical high-resolution (20 km) model coupled with a visco-elastic bedrock model. The melt-and-runoff model is based on the positive-degree day method and includes meltwater retention in the snowpack and the formation of superimposed ice. The AOGCM is a coarse resolution model without flux correction based on the LMD 5.3 atmospheric model coupled with a primitive-equation, free-surface oceanic component incorporating sea ice (CLIO). By 2100, average Greenland annual temperature is found to rise by about 4.5°C and mean precipitation by about 35 %. The total fresh water flux approximately doubles over this period due to increased runoff from the ice sheet and the ice-free land, but the calving rate is found to decrease by 25%. The ice sheet shrinks equivalent to 4 cm of sea-level rise. The contribution from the background evolution is not more than 5 %. We did not find significant changes in the patterns of climate change over the North Atlantic region compared with a climate change run without Greenland fresh water feedback.

Description: Results are presented from a climate change simulation obtained from an atmosphereoceangeneral circulation model coupled with a three-dimensional model of the Greenlandice sheet. The experiment covers the period 1970-2100 and is driven by the midrangeIPCC SRES B2 scenario. The Greenland model is a high-resolution (20 km)thermomechanical model that includes a visco-elastic solid Earth model. The meltand-runoff model is based on the positive-degree day method and includes meltwaterretention in the snowpack and the formation of superimposed ice. The AOGCM is acoarse resolution model without flux correction based on the LMD 5.3 atmosphericmodel coupled with a primitive-equation, free-surface oceanic component incorporatingsea-ice (CLIO). In the coupling procedure, the ice-sheet model receives temperatureand precipitation changes from the AOGCM in anomaly mode and passes theannual spatial and temporal distribution of the different fresh water flux componentsback into the ocean. In the experiment, average Greenland temperature rises by about4C by 2080, but cools abruptly through a weakening of the North Atlantic thermohalinecirculation to near-present values by the end of the 21st century. This behaviour iscaused by the increased meltwater flux from the ice sheet itself. The total fresh waterflux approximately doubles over the first 100 years due to increased runoff from theice sheet and the ice-free land, but the calving rate is found to decrease by 25% overthe same period. The ice sheet shrinks equivalent to about 5.5 cm of sea-level rise.

Description: A series of climate-change projections are conducted with LOVECLIM, a three-dimensional Earth system model of intermediate complexity that consists of a quasi-geostrophic atmospheric model (ECBILT), an ice-ocean general circulation model (CLIO), a dynamical model of the terrestrial biomass (VECODE), a thermomechanical model of the Greenland and Antarctic ice sheets (AGISM), and a model of the oceanic carbon cycle (LOCH). The global carbon cycle in the model is simulated by both VECODE and LOCH. ECBILT takes into account the topography and surface albedo changes computed by the ice-sheet model. CLIO accounts for the freshwater and latent heat fluxes resulting from the melt of the ice sheets and icebergs. The forcing of the AGISM by ECBILT-CLIO is considered in perturbation mode to avoid any systematic errors and to deal with the rather coarse-resolution of the climate model. We first perfom simulations with prescribed carbon-dioxyde concentrations in order to compare the model results with other studies.An ensemble of experiments over the last 500 years is first carried out aiming at validating the model against recontructions (Figures 1 and 2). The model is forced by two natural forcings: the changes in solar irradiance and volcanic eruptions. The anthropogenic forcings considered are the increase in greenhouse-gas concentrations, including troposheric ozone, as well as the evolution of the sulphate-aerosol load in the atmosphere. The model also accounts for the land-cover changes due to human activities.Climate changes during the 21st century are then studied through ensemble simulations performed with the model driven by various IPCCs SRES scenarios for greenhouse-gas and sulphate-aerosol concentrations. The model performance is assessed by comparing its results with similar results obtained by climate general circulation models.Idealised experiments are finally performed over the third millennium focusing mainly on the North Atlantic climate. In those simulations, the forcings are fixed to their 2100 values until the end of the millennium. A particular attention is paid to the change in freshwater flux from the Greenland ice sheet and its possible impact on the World Oceans thermohaline circulation. A sensitivity study over the third millenium is also carried out in order to assess the ice-sheet contribution to the modelled future climate change

Description: A three-dimensional global model of the Earth system suitable for studying the long-term evolution of climate (LOVECLIM) has been recently developed. This model is made up of a coarse-resolution three-dimensional atmospheresea-iceocean model (ECBILTCLIO), a dynamical model of the continental biosphere (VECODE), a comprehensive model of the oceanic carbon cycle (LOCH), and a high-resolution thermomechanical model of the Greenland and Antarctic ice sheets (AGISM). The atmospheric component has the big advantage that it has been simplified to a level that makes runs on a multi-century time-scale computationaly feasible, while at the time, producing results that, on the whole, are comparable to those of atmospheric general circulation models. The performance of the coupled model is evaluated by performing ensemble simulations over the period 15002000 and by comparing the model results to climate reconstructions available. In these simulations, the following forcings are taken into consideration : the variations in solar irradiance, the volcanic activity, the anthropogenic emissions of CO2, and the changes in concentration of other greenhouse gases and sulphate aerosols resulting from human activities. In the future, the model will be used to investigate the evolution of climate and sea level over the third millennium.