Response of the Gulf Stream transport to characteristic high and low phases of the North Atlantic Oscillation

We investigate an ambiguity in the current understanding of the Gulf Stream (GS) transport in response to the North Atlantic Oscillation (NAO). While some investigations (discussed herein) suggest enhanced transport during low NAO phases, other studies suggest enhanced transport in high NAO phases. NAO-induced variability in the western North Atlantic is studied by using a 1/6°-resolution basin-scale Regional Ocean Modeling System (ROMS) model. Results indicate that the western boundary current limb of the GS, upstream of Cape Hatteras, exhibit enhanced transport during low-NAO phases. However, further downstream of Cape Hatteras, after the GS separates from the coast, diminished GS transport is seen during low-NAO phases. The converse is true for high NAO phases for both segments of the GS system. Model results show the Deep Western Boundary Current (DWBC), the northern recirculation gyre and the southern recirculation gyre intensify (weaken) during the high (low) NAO periods.

► The Gulf Stream separation occurs later (earlier) during the high (low) NAO phase
► Gulf Stream path after separation is north (south) of its mean path during high (low) NAO. Difference of 55 km between the phases.
► The Gulf Stream transport is weaker (stronger) near Florida Strait but stronger (weaker) after separation during high (low) NAO phases.
► The Deep Western Boundary Current, the northern and southern recirculation gyre intensify (weaken) during the high (low) NAO phases.