Multidecadal variability in the Arctic/North Atlantic climate system

Over the last several decades, the Arctic and North Atlantic have undergone substantial changes. Enhanced transport of warmer air from lower latitudes led to increased arctic surface air temperature associated with decreased arctic sea-level pressure and increased polar atmospheric cyclonicity which led to reductions in arctic ice extent and a decrease of ice thickness. Changes in the Arctic Ocean are also significant. Positive temperature anomalies in the intermediate Atlantic Water (AW) layer of the Arctic Ocean were found in the 1990s and 2000s. Freshwater content in the upper layer of the Arctic Ocean was also reduced dramatically over the recent decades. Concurrent with these high-latitude changes are North Atlantic warming and salinification in the upper 300 m layer (except the subpolar North Atlantic) and widespread cooling and freshening in the 1000-3000 m layer. We suggest that both long-term climate trend and low-frequency variability play a substantial role in shaping these recent changes in the Arctic/North Atlantic climate system. Understanding the key factors influencing the Arctic/North Atlantic multi-decadal variability may provide a reasonable means for developing climatic forecasts of widespread persistent anomalies. Xiangdon