Changes of Air-sea Coupling in the North Atlantic over the 20th Century

Changes of air-sea coupling in the North Atlantic Ocean over the 20th century are investigated using reanalysis data, climate model simulations, and observational data. It is found that the ocean-to-atmosphere feedback over the North Atlantic is significantly intensified in the second half of the 20th century. This coupled feedback is characterized by the association between the summer North Atlantic Horseshoe (NAH) SST anomalies and the following winter North Atlantic Oscillation (NAO). The intensification is likely associated with the enhancement of the North Atlantic storm tracks as well as the NAH SST anomalies. Our study also reveals that most IPCC AR4 climate models fail to capture the observed NAO/NAH coupled feedback.