Sub-surface signatures of the Atlantic Multidecadal Oscillation

Sub-surface signatures of the Atlantic Multidecadal Oscillation (AMO) are identified using expendable bathythermograph (XBT) measurements of temperature from the surface down to a depth of 400 m. Basin averaged temperature anomalies in the North Atlantic at different depths display multidecadal variability with a phase shift between temperature anomalies at the surface and at depth. Westward propagation of temperature anomalies is observable at depth and there is a lag correlation between east-west and north-south temperature gradients, with the east-west temperature gradient leading. These sub-surface characteristics of the AMO agree with those expected from the noise-driven internal ocean mode view of the AMO, as derived from a hierarchy of ocean-atmosphere models.