Accelerated North Atlantic climate variability triggered by increased seasonal melt

Freshwater plays a key role in the Arctic - North Atlantic climate system. On the one hand, it has been suggested as a precursor of large-scale weather extremes and as a potential trigger of rapid climate changes in the past. On the other hand, it is, itself, a sensitive climate change indicator that increases in response to the melting cryosphere. Yet, future risks arising from enhanced glacial and sea ice melt remain difficult to assess due to the complexity of the involved ice-ocean-atmosphere feedbacks and the interference of signals on different timescales. Combining observations, models, theory, and a sophisticated statistical approach, we demonstrate the central role of freshwater anomalies in North Atlantic climate variability over the last 70 years, assess the extent to which they have been contributing to weather extremes, and discuss the risk of a more fundamental climate change under increased freshwater fluxes in future.