Determining North Atlantic meridional transport variability from pressure on the western boundary: A model investigation

[1] In this paper, we investigate the possibility of determining North Atlantic meridional transport variability using pressure on the western boundary, focusing on the 42°N latitude of the Halifax WAVE array. We start by reviewing the theoretical foundations of this approach. Next, we present results from a model analysis, both statistical and dynamic, that demonstrate the feasibility of the approach. We consider how well we can quantify the meridional transport variability at 42°N given complete knowledge of bottom pressure across the basin and to what degree this quantification is degraded by first ignoring the effect of intervening topography and then by using only bottom pressure on the western boundary. We find that for periods of greater than 1 year, we can recover more than 90% of the variability of the main overturning cell at 42°N using only the western boundary pressure, provided that we remove the depth-averaged boundary pressure signal. This signal arises from a basin mode of bottom pressure variability, which has power at all time scales, but that does not in truth have a meridional transport signal associated with it, and from the geostrophic depth-independent compensation of the Ekman transport. An additional benefit of the removal of the depth-averaged pressure is that this high-frequency Ekman signal, which is essentially noise as far as monitoring the meridional overturning circulation for climatically important changes is concerned, is clearly separated from other modes.

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