Pesquisadores do GT3.0 (Variabilidade climática, ciclos biogeoquímicos e fluxo de CO2 no oceano Atlântico tropical) do inctAmbTropic participaram de um trabalho recente publicado no Global Biogeochemical Cycles (IF = 5.703) sobre trocas de CO2 no Oceano Atlântico Tropical mostrando que as águas da pluma do rio Amazonas funcionam como um sumidouro de CO2 sendo responsáveis por cerca de 87% da absorção de CO2 no Oceano Atlântico Tropical Ocidental. O trabalho intitulado "Contrasting Sea-Air CO2 Exchanges in the Western Tropical Atlantic Ocean" tem como autores Thiago Monteiro, Matheus Batista, Sian Henley, Eunice da Costa Machado, Moacyr Araújo e Rodrigo Kerr.
Principais correntes superficiais que caracterizam a dinâmica do Oceano Atlântico Tropical Ocidental.
The western Tropical Atlantic Ocean is a biogeochemically complex region due to the structure of the surface current system and the large freshwater input from the Amazon River coupled with the dynamics of precipitation. Such features make it difficult to understand the dynamics of the carbon cycle, leading to contrasting estimates in sea-air CO2 exchanges in this region. Here, we demonstrate that these contrasting estimates occur because the western Tropical Atlantic Ocean can be split into three distinct sub-regions in terms of the sea-air CO2 exchanges. The sub-region under the North Brazil Current domain acts as a weak annual CO2 source to the atmosphere, with low interannual variability. The sub-region under the North Equatorial Current influence acts as an annual CO2 sink, with great temporal variability. The third sub-region under the Amazon River plume influence shows greater interannual variability of CO2 exchanges, but it always acts as a net oceanic sink for CO2. Despite this large spatial variability, the entire region acts as a net annual CO2 sink of −1.6 ± 1.0 mmol m−2 day−1. Importantly, the Amazon River plume waters drive 87% of the CO2 uptake in the western Tropical Atlantic Ocean. In addition, we found a significant increasing trend in sea surface CO2 partial pressure in the North Brazil Current and North Equatorial Current waters. Such trends are more pronounced than the increase in atmospheric CO2 partial pressure, revealing the sensitivity of carbon dynamics in these sub-regions to global climate change.
O trabalho completo pode ser acessado em:
Pesquisadores dos GTs 2.1 (Geodiversidade, Biodiversidade e Recursos Vivos da Plataforma Continental) e 3.0 (Variabilidade climática, ciclos biogeoquímicos e fluxo de CO2 no oceano Atlântico tropical) do inct AmbTropic II publicaram no Journal of Marine Sciences (IF: 2.542) um interessante trabalho que investiga as interações entre a topografia submarina e a circulação na região nordeste do Brasil. Esta interação pode ser considerada como um conjunto de processos que resultam da interação entre as correntes e gradientes topográficos especialmente aqueles associados com canyons submarinos, que apresentam um potencial para produzir ressurgência e transporte "cross-isobath" em margens continentais. O trabalho intitulado "Flow-topography interactions in the western tropical Atlantic boundary off Northeast Brazil" tem como autores Marcos V.B. Silva, Beatrice Ferreira, Mauro Maida, Syumara Queiroz, Marcus Silva, Humberto L. Varona, Tereza C.M. Araújo e Moacyr Araújo.
Flow-Topography Interaction can be considered as a particular set of processes resulting of the currents inter- action with a topographic gradient, specially associated with submarine canyon areas, which are important morphological features with potential to upwelling and cross-isobath transport on the continental margins. The South Pernambuco Continental Shelf (SPCS) and Pernambuco Plateau located on the Southwestern Tropical Atlantic (SWTA), present incised morphological features, highlighting the shelf valleys and blind canyons, which do not have a connection to the shelf or an onshore river system. They are likely features for interactions between the dominant along-shelf flow represented by the strong western boundary North Brazil Undercurrent. We investigated potential canyon induced upwelling and the respective mechanisms at the late spring/early fall context. CTD and reanalysis data from GLORYS12V1, and in situ bathymetric measurements were used to characterise the hydrodynamics and canyon morphology, respectively. Then, we combined both to obtain dimensionless numbers from dynamical scale analysis to infer possible imbalances of the acting forces. Rean- alysis data evidenced uplift at the slope not related to the blind canyons. CTD data indicated a seasonal variation of the intrusion of water masses, especially at the shelf-break for the Middle shelf valley and Campas shelf valley. A temperature difference of 2.5 ◦ C (2.0 ◦ C) between surface and deep waters was observed during the late spring. A stepwise temperature structure was present in both seasons, indicating instability below the mixed layer depth, the uplifting of isotherms, and the corrosion of the lower portion of the surface mixed layer. The dimensionless parameters analysis reveals highest Rossby values during the fall, mainly in Zieta shelf valley (R0=130.87) and Csv (R0=111.71), and lower values for the canyons of the Pernambuco Plateau. Our hypothesis is that the shelf valleys might play a role in conducting the uplifted slope water coast-ward. For the blind canyons, although no related upwelling was observed, reanalysis revealed the presence of a deep anti-cyclonic eddy at one of the blind canyon’s mouth. Rossby and Burger numbers indicate a weak geostrophic balance at the canyon rim, and instability of the horizontal length scale of the pressure gradient force, with tendency to vorticity control. While the paradigm that shelf and coastal waters off north-eastern Brazil are mostly oligotrophic in the surface is true, our observation of shallow (<60 m) subsurface uplift should be considered in future works in the SWTA.
O trabalho completo pode ser acessado em: https://doi.org/10.1016/j.jmarsys.2021.103690
Foi publicado em maio de 2021 o relatório completo do TAOS (Tropical Atlantic Observing System) que teve entre seus autores principais o prof. Moacyr Araujo, coordenador do do GT3.0 (Variabilidade climática, ciclos biogeoquímicos e fluxo de CO2 no oceano Atlântico tropical) do inctAmbtropic. O relatório resume os resultados de duas oficinas realizadas e discussões subsequentes do comitê revisor, incluindo contribuições de outros membros da comunidade de pesquisadores que atuam no Atlântico Tropical (você pode fazer o "download"do relatório ao final desta postagem).
Abaixo alguns trechos do Resumo Executivo:
"The tropical Atlantic is the smallest of Earth’s tropical ocean basins, one half the width, west to east, of the tropical Indian Ocean and less than one fifth that of the tropical Pacific. Thus, the tropical Atlantic interacts intimately with its bordering lands, strongly influencing their weather and climates, and it is readily accessible by the region’s inhabitants. At the same time, the tropical Atlantic plays an outsized role in the global climate system. Through the Atlantic Meridional Overturning Circulation (AMOC), it delivers nearly half a petawatt of energy from the Southern to the Northern Hemisphere, and it has marked, if still not fully understood, impacts on globally significant variations in the tropical Indian and Pacific Oceans"
"All countries bordering the tropical Atlantic experience important societal challenges driven by regional ocean processes and air-sea-land interactions. These are exacerbated by climate change, which induces new emerging threats. Examples include floods and droughts in South America and West Africa, more intense storms and hurricanes, and continuing sea-level rise that increases flooding risks and episodes of coastal erosion. Other regional emerging extreme events such as ocean heat-waves and episodes of anoxia and acidification amplify the vulnerabilities of regional marine ecosystems – systems already stressed by overfishing and pollution. Moreover, recent studies show that the tropical Atlantic has two-way connections with the Pacific and appears to play a driver role in mid- and high-latitude climatic events including the occurrence of impactful mid-latitude extremes throughout the year)".
"The present TAOS review comes at an inflexion point for the tropical Atlantic, where scientific progress, demands on its resources, and environmental changes resulting from local and global stressors simultaneously are accelerating. At this juncture, there are great rewards to be reaped from an enhanced and invigorated TAOS, rationally planned and responsibly governed and coordinated. This report offers the rationale and the strategy for achieving a TAOS that will be well suited to serve the societal and scientific needs of the Atlantic basin and the globe over the coming decades. The recommended enhancements to the observing system across the range of platforms, with their associated sampling timescales, variables measured, and ranges of depths is expected lead to improved forecasts and projections of phenomena ranging from daily weather, fisheries and coastal managements, to anthropogenic climate change over multiple decades".