Transformations and pathways of Southern Ocean waters into the South Atlantic Ocean

• Main Author: Olivé Abelló, Anna
• Other Authors: Pelegrí Llopart, Josep L. (Josep Lluís), Machín Jiménez, Francisco, Universitat de Barcelona. Facultat de Ciències de la Terra
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universitat de Barcelona 2023
• Subjects: Oceanografia; Circulació oceànica; Atlàntic; Oceà; Oceanography; Ocean circulation; Atlantic Ocean; Southern Ocean; Drake Passage; Scotia Sea; South Scotia Ridge; South Atlantic Ocean
• Online Access: http://hdl.handle.net/2445/204661; http://hdl.handle.net/10803/689534

[eng] The returning limb of Atlantic Meridional Overturning Circulation (AMOC) is partly supplied by the cold-fresh waters that enter through the Drake Passage. Up to the isoneutral 28.0 kg m−3, the mean water inflow through the Drake Passage to the Scotia Sea is 140.8 ± 7.4 Sv and the outflow through the Northern Passages is 115.9 ± 8.3 Sv. Below this isoneutral reference and down to 2000 m, an additional 23.4 Sv enters through the Drake Passage. The mean barotropic contribution always represents over half the total transports, with substantial seasonal and moderate interannual variability in the water transports. The water mean-residence time is about 6 - 8 months. Combining the Argo floats data with other observational measurements, we apply a climatological high-resolution inverse model over the Scotia Sea boundaries up to the 28.0 kg m-3 isoneutral. The ACC enters 136.7 ± 1.0 Sv through the Drake Passage and exits 137.9 ± 1.0 Sv through the northern boundary, with the difference responding to the South Scotia Ridge and Philip Passages contributions. Along its northward path, the ACC waters lose heat but gain equatorward freshwater transport. Within the Scotia Sea, the surface-modal and modal-intermediate waters experience production in all biogeochemical variables. Finally, regarding anthropogenic DIC, the Scotia Sea stores 0.123 Pg C yr-1. Then, the ROD method compares actual drifters' displacements with numerical trajectory predictions; the observed-predicted differences in final positions respond to diffusive motions not captured by the numerical models. The ROD method is applied in the western South Atlantic Ocean leading to maximum diffusivities of 4630 - 4980 m2 s-1 in the upper 200 m of the water column, presenting an inverse relationship with depth. The diffusivities near the surface are fairly constant in latitude but the diffusion coefficients at 1000 m decrease considerably south of the Southern Boundary. With the horizontal diffusion coefficients obtained previously, we use the Lagrangian ...