| Summary: | The North Atlantic Oscillation is the dominant mode of winter climate variability in the Northern hemisphere. It is a complex 'see-saw' between two pressure systems located over Greenland and a group of Islands known as the Azores. The North Atlantic Oscillation is most pronounced during the winter season and accounts for more than one third of the total variance in sea level pressure. The North Atlantic Oscillation is closely related to the position of the storm track. During a positive phase of the North Atlantic Oscillation the average storm track moves across the North Atlantic in a North Easterly direction towards Europe and the United Kingdom, During a negative phase of the North Atlantic Oscillation, the storm track moves in a West to East direction towards Southern Europe. Another track associated with the negative phase of the North Atlantic Oscillation moves in a Northerly direction along the coast of North America. The frequency and intensity of storms crossing the North Atlantic is also related to the phase of the North Atlantic Oscillation, but to a lesser degree (the North Atlantic Oscillation accoimting for approximately 20% of their variation). The North Atlantic Oscillation has been experiencing an upward frend over the last thirty years becoming predominantly positive. In can be said that the upward trend is partially attributed to increasing greenhouse gas emissions; including the anthropogenic and human influences on sea level pressvire, however this must be proved by model simulations and further research.
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