High latitude cyclones, variability, trends and impacts

Cyclones are important transporters of energy into the Arctic either directly or by modulating the ocean currents. In addition, the Arctic region is a moisture flux convergence area and the atmospheric water transported into the area by cyclones, is a major part of the freshwater input to the Arctic Ocean, either directly through precipitation over the ocean/sea ice or as precipitation over land which is then transported into the Arctic Ocean as river runoff. Variability and possible future changes in high latitude cyclones are therefore of great importance for the Arctic climate and ecosystem. Results highlighting the direct and indirect influence of cyclones on sea ice and ocean variability in the north Atlantic sector will be presented. Results using atmospheric reanalysis indicate an upward trend in the number and intensity of cyclones entering the Arctic. This is particularly pronounced for cyclones entering the Arctic from the north Atlantic side. Is these observed trends reproduced by global coupled models run with increasing greenhouse gasses? Results based on the coupled models participating in the IPCC AR4 will be presented.