Observation-based estimates of volume, heat, and freshwater exchanges between the subpolar North Atlantic interior, its boundary currents, and the atmosphere

Abstract. The Atlantic Meridional Overturning Circulation (AMOC) transports heat and salt between the tropical Arctic oceans. interior of North subpolar gyre (SPG) is responsible for much water mass transformation in AMOC, export this to intensified boundary currents crucial projecting air–sea interaction onto strength AMOC. However, magnitude location exchange SPG remains unclear. We present a novel climatology using quality-controlled CTD (conductivity–temperature–depth) Argo hydrography, defining as oceanic region bounded by 47? N 1000 m isobath. From hydrography we find geostrophic flow out around with minimal seasonality. horizontal density gradient reversed western Greenland, where into SPG. Surface Ekman forcing drives net all seasons pronounced seasonality, varying 2.45 ± 0.73 Sv summer 7.70 2.90 winter. estimate advected be 0.14 0.05 PW winter 0.23 spring, freshwater 0.07 0.02 0.15 autumn. These estimates approximately balance surface fluxes over domain. varies seasonally, minimum 6.20 1.40 autumn maximum 10.17 1.91 most likely mediator variability. overturning at 27.30 kg m?3, second, smaller 27.54 m?3. Upper waters (?0<27.30 m?3) are transformed then exported either intermediate (27.30–27.54 Current (NAC) or dense (?0>27.54 exiting south. Our results support consensus that formation pre-conditioning Subpolar Mode Water north-eastern key determinant AMOC strength.