Abyssal ocean overturning shaped by seafloor distribution
Résumé
The abyssal ocean is broadly characterized by northward flow of the densest waters and southward flow of lighter waters above. Understanding what controls the strength and structure of these inter-hemispheric flows, referred to as the abyssal overturning circulation, is key to quantifying the ocean's ability to store carbon and heat on timescales exceeding one century. Here we show that, north of 32ºS, the depth distribution of the seafloor compels dense southernorigin waters to flow north below ~ 4 km depth and to return south predominantly deeper than 2.5 km. Unless ventilated from the north, the overlying mid-depths (1-2.5 km) host comparatively weak mean meridional flow. Backed by a new analysis of historical radiocarbon measurements, the findings imply that the geometry of the Pacific, Indian and Atlantic basins places a major external constraint on the overturning structure.
Domaines
Planète et Univers [physics]
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