On the Role of the Labrador Sea in Controlling the North Atlantic Oscillation

The atmospheric response to a sea-ice anomaly and sea surface temperatures in the Labrador Sea is investigated by means of an AGCM. The simulated response resembles the North Atlantic Oscillation (NAO) pattern in the low-level pressure field, with low temperatures and heavy ice conditions in the Labrador Sea being associated with a low NAO index. The result indicates that atmospheric response to changes in the sea ice and sea surface temperatures in the Labrador Sea might constitute a negative feedback which can cause phase shifts in the NAO. The result is also consistent with the hypothesis that heavy ice conditions perturbes the region of strong baroclinicity in the entrance to the North Atlantic storm track southwards.