The role played by density in meso and large scale ocean dynamics

• Ano de defesa: 2020
• Autor(a) principal: Lage, Mariana Miracca
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: buoyancy; empuxo; first baroclinic mode; modos verticais; ondas de Rossby; primeiro modo baroclínico; Quase geostrofia de superfície; Quase-geostrofia; Quasi-geostrophy; Rossby waves; Surface quasi-geostrophy; vertical modes
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/21/21135/tde-10082022-142820/

Sea surface height is key in ocean dynamics. Nowadays, level 4 satellite products based on multiple nadir looking altimeters can resolve horizontal scales of around 100 km, which is enough to study meso to large scale dynamics [O(102 103) km] but miss smaller scale features [O(10 102) km]. Using outputs from a general ocean circulation model, we reconstructed the streamfunction using sea surface buoyancy under the surface quasi-geostrophy (SQG) theory to determine which dynamical regime classical quasi-geostrophy (QG) or SQG dominates the sea surface height signal in the mesoscale range at 11°S, 24.5°S and 34.5°S on the South Atlantic. At these latitudes, analyses of sub-areas show that this dominance is related to the seasonal cycle of the mixed layer and the amount of eddy kinetic energy in the mesoscale. The sea surface height reconstruction under the SQG theory is better in winter, and SQG dominates in high eddy kinetic energy regions. Subsequently, we focused in Rossby wave dynamics. We identified long, first mode baroclinic Rossby waves in sea surface anomaly altimeter data using a 2D Finite Impulsive Response filter in the three ocean basins of the Southern Hemisphere. Then, we reconstructed the sea surface height anomaly applying a traditional QG vertical mode decomposition in the numerical model outputs and evaluated the contribution of stratification to the modulation of the Rossby waves amplitudes: the more stratified the water column, the larger the amplitudes of the Rossby waves. The results shed a light on the interplay between surface and interior dynamics, connecting the ocean surface expression to the interior stratification. With the upcoming higher resolution altimeters, the analyzes can be extended towards finer scales, which will lead to a better characterization of processes that may influence the variation of potential vorticity, other than stratification, and thus modifying the sea surface height field and consequently Rossby waves characteristics.