Impact of Greenland Ice Sheet Melt on Future AMOC Evolution

The evolution of the AMOC is one of the key uncertainties of future climate projections. The latest IPCC report states that state-of-art climate models show an AMOC reduction over the 21^st century of 20-30% for the RCP4.5 scenario and 36-44% for RCP8.5. Moreover, it is found to be very unlikely that the AMOC will undergo an abrupt transition or collapse in the 21^stcentury. However, during the last decade a strong increase in mass loss of the Greenland Ice Sheet has been observed, a trend that is expected to continue into the future. This enhanced melt water input to the North Atlantic provides a major uncertainty in the evolution of the AMOC that has thus far not been taken into account in the RCP projections.

Based on observations and high resolution regional climate modeling, we have constructed state-of-the-art projections of changes in the surface mass balance of the Greenland Ice Sheet for the period 2006-2300, both for RCP4.5 and RCP8.5. The developed methodology enables the inclusion of Greenland Ice Sheet surface mass balance changes in GCM climate change projections, either as a forcing or as a climate feedback through the coupling with upper air temperature changes. These surface mass balance projections form the basis of a major model-inter-comparison effort that allows us to assess i) the potential impact on the AMOC evolution of changes in the Greenland Ice Sheet over the course of the next three centuries, ii) assess the likelihood of an AMOC collapse and iii) investigate how a potential weakening of the AMOC could in turn influence the surface mass balance of the Greenland Ice Sheet.