AOPP Seminar - Mapping the Ocean energy pathways

The complexity of the Ocean circulation lies in flows spanning several orders of magnitude in space and time. To achieve a balance, the highly energetic flows at large-scale must transfer energy across scales, ultimately down to the dissipative scale. Much progress has been made in describing kinetic energy (KE) pathways from basin scales (L ~ 100km; months -- years) to the mesoscale range (L ~ 10km -- 100km; T about weeks -- months). However, questions remain about the pathways between the mesoscale and the intermediate scale, known as the submesoscale (L ~ 0.1km -- 10km; T ~ hours -- day). This range was challenging to observe and model until recently, due to its relatively elusive nature, and is too large to experimentally reproduce. My work focuses on unravelling the energy pathways across spatiotemporal scales using a combination of theory, state-of-the-art models, and remote sensing. In the subtropical gyre of the North Atlantic Ocean, the western boundary current distinctively stands out from the rest of the gyre. There, the generation of mesoscale eddies dominates, while tides constitute the primary forcing in the rest of the gyre, and the high-frequency wind forcing weakly contributes over the whole gyre. In the Indian Ocean, the model-inferred net mesoscale energy source at the western boundary current was successfully reproduced from satellite altimetry, although underestimated due to approximations required for inferring a 3D diagnostic from 2D surface fields. In this region, the mesoscale eddies generation competes with intense, but somewhat weaker, mesoscale energy sinks channelled by topographic interactions. Away from large topographic constraints, smaller scale flows channel an upscale energy flux, energising mesoscale eddies, up to a comparable magnitude that their generation processes. This exerts feedback from small to large scales of potential climatic relevance, especially in the context of an increasing eddying Ocean.