The North Atlantic Oscillation (NAO) is generally accepted as being an inter-annual oscillation in the atmospheric mass field. The positive phase of the NAO is associated with a strong Icelandic Low and is the result of storms that track in a northeasterly direction towards Greenland. The negative phase has a substantially weaker Icelandic Low or a blocking high over Greenland and is the result of storms that track in an easterly direction across the North Atlantic. In this paper we show that NAO-like regime shifts occur on intra-annual timescales as well. The impact of these changes in flow regime on the spatial distribution of air-sea fluxes over the basin will be discussed.