Deep Argo Observations of Buoyancy Redistribution in the Atlantic Overturning

Abstract The steady‐state buoyancy budget of the Atlantic Meridional Overturning Circulation (AMOC) balances water mass transformation with meridional export. Using historical ocean data, Deep Argo observations, and atmospheric reanalysis, we assess the residual of this balance—water mass volume trends—and its role in the transformation budget of the Subpolar North Atlantic and Nordic Seas on interannual to bidecadal timescales. On long timescales, volume trends in deep convective seas can be large but the volume expansion or contraction of the upper and lower AMOC limbs remain minimal, suggesting that water mass transformation and AMOC intensity may be interchangeable. Conversely, interannual trends are larger across all regions and all density ranges. The volume of the AMOC limbs is significantly impacted so relationships with transformation rates can only be established when considering the timescales of the southward export of transformed water masses out of the subpolar domain.