The Relative Contribution of the Water Masses to the Sea Level Variation in the South Atlantic

• Ano de defesa: 2023
• Autor(a) principal: Rocha, Thamirys Cavaton
• 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: Água Central do Atlântico Sul; Água Circumpolar; Água Intermediária Antártica; Água Profunda do Atlântico Norte; Água Tropical; Antarctic Intermediate Water; Circumpolar Deep Water; espessura das massas d'água por efeitos estéricos; North Atlantic Deep Water; South Atlantic Central Water; Tropical Surface Water; Water-mass layer thickness due to steric contribution
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/21/21135/tde-29052023-141351/

The sea level changes due to steric contributions have become more relevant in the past decades because oceans store the largest part of the heat from anthropogenic greenhouse gas emissions. Recent studies showed evidence that the sea level variation is mainly attributed to the first 2000 m of the water column. Therefore, our purpose was to quantify how much of the individual water masses variation is correlated to the sea level changes. To quantify the layer thickness variability of the Tropical Surface Water (TSW), South Atlantic Central Water (SACW), Antarctic Intermediate Water (AAIW), Circumpolar Water (CDW), the North Atlantic (NADW), and the lower layers (LOWER), we used WOA18 data, altimetric satellites data, and the outputs from ECCO and HYCOM models. The layer thickness had seasonal and interannual variability, but only the TSW, SACW, and AAIW were consistent between the models. The main process observed on ECCO analysis was an alternating expansion and contraction between consecutive water masses, while on HYCOM, only the LOWER expanded and the other water masses contracted. The TSW (ECCO) showed the largest contribution (44% to 90%) to the sea level, followed by the SACW (0% to 44%), AAIW (0% to 44%), UCDW (~11%), UNADW(~11%), and LOWER (5%) between 0ºS and 40ºS. The TSW was the only water mass whose relative explained variance decreased southward, while the other five water masses increased southward. The SACW and AAIW had a higher explained variance (11% - 88%) between 40ºS to 50ºS, and the LOWER had the highest value (>44%) between 50ºS and 55ºS. HYCOM results were similar to ECCO, except that the TSW explained variance was higher (44% to 90%) only between 0ºS to 25ºS and SACW (44% to 90%) was between 25ºS to 45ºS. The correlation between the altimeter sea level and ECCO showed higher values (>70%) from 0ºS 10ºS to 40ºW--15ºE. This indicates that the hypothesis of this work is valid for this region. Even though HYCOM presented a correlation higher than 75% for most of the basin, the layer thickness variability showed inconsistencies with previous studies.