How Would the 2014 Winter with the Anomalous Polar Vortex Look like in 2100?

Wednesday, 17 December 2014
Lucinda Rasmijn1, Gerard van der Schrier2, Jan Barkmeijer2, Andreas Sterl2 and Wilco Hazeleger2, (1)Royal Netherlands Meteorological Institute, De Bilt, 3730, Netherlands, (2)Royal Netherlands Meteorological Institute, De Bilt, Netherlands
We study in detail the 2014 winter with floods which devastated parts of Britain and extreme winter conditions at the east coast of North America. The event was associated with an anomalous Arctic polar vortex. Using a novel developed forced sensitivity tool, we reproduce the large-scale atmospheric circulation which led to this extreme climatic event in a fully coupled climate model. The same tool is now used in a future climate to reproduce this event under warmer 2100 conditions. We use initial conditions from an RCP8.5 scenario simulation of EC-Earth and use the forced sensitivity tool, which produces optimal model tendency perturbations, to force the large-scale atmospheric circulation to reproduce the anomalous vortex in the fully coupled model. We find that, with the same large-scale atmospheric circulation as that of the winter of 2014, in the future climate simulations baroclinic activity over the east coast of North America is greatly reduced, despite the flow of Arctic air over the continent during the event. As a result of this, less cyclones are transported to Europe resulting in much smaller precipitation amounts in Western Europe. Also in the future climate simulations no anomalous cold wave is found over the east coast of North America due to a reduced north-south temperature gradient as a result of Arctic amplification. This particular case shows that some climatic extremes will become less severe in the future. The results of this study will be presented to the audience, as well as a brief description of the method applied.