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: Two simulations of the 21st century climate have been carried out using, on the one hand, a coarse resolution climate general circulation model and, on the other hand, the same model coupled to a comprehensive model of the Greenland ice sheet. Both simulations display a gradual global warming up to 2080. In the experiment that includes an interactive ice sheet component, a strong and abrupt weakening of the North Atlantic thermohaline circulation occurs at the end of the 21st century. This feature is triggered by an enhanced freshwater input arising mainly from a partial melting of the Greenland ice sheet. As a consequence of the circulation decline, a marked cooling takes place over eastern Greenland and the northern North Atlantic. This result underlines the potential role of the Greenland ice sheet in the evolution of climate over the 21st century.

Description: We present results from a climate change experiment obtained from an atmosphere-ocean general circulation model that is fully interactively coupled with a three-dimensional model of the Greenland ice sheet. The experiment covers the period 1970-2100 and is driven by the IPCC SRES B2 scenario. The Greenland model is a thermomechanic high-resolution (20 km) 3D model coupled with a visco-elastic bedrock model. The melt-and-runoff model is based on the positive-degree day method with parameters obtained from a new calibration on available data and includes meltwater retention in the snowpack and the formation of superimposed ice. The AOGCM is a coarse resolution model without flux correction. Its atmospheric component is based on version 5.2 of the AGCM developed at the "Laboratoire de Météorologie Dynamique" of the CNRS (Paris). The OGCM is a primitive-equation, free surface model incorporating sea-ice developed at Louvain-la-Neuve (CLIO). The ice sheet model uses temperature and precipitation perturbations provided by the AOGCM and provides the spatial and temporal distribution of the fresh water released back into the ocean to investigate its effects on the thermohaline circulation in the North Atlantic.Various terms of the mass-balance such as runoff from the ice sheet, runoff from land, calving and basal melt are calculated for a control experiment arising from the background evolution in response to the last glacial cycle, and for a climatically forced experiment. For the 21st century, we find that the annually averaged temperature forcing increases from 3*C in south Greenland to more than 6*C in the northern parts of the ice sheet, while the mean precipitation increases by between 30 and 50 %. The total fresh water flux approximately doubles over this period due to increased runoff from the ice sheet and the ice-free land, whereas the calving rate is found to decrease by 25% over the same period. The ice sheet shrinks equivalent to about 3 cm of sea-level rise. The contribution from the background evolution is not more than 5 %. We did not find significant changes of the thermohaline circulation and the general patterns of climatic change as compared to a control run with the AOGCM using a constant Greenland fresh water flux.