de Freitas P. P., Cirano M., Teixeira C. E. P., Melres S. J. R., de Sousa Akcd, Gomes V. J. C., Guerrero-Martin C. A., Koch Larrouy Ariane. (2025). Spatial and temporal variability of hydrodynamics on the Amazon Continental Shelf : an observational approach. Continental Shelf Research, 291, p. 105491 [17 p.]. ISSN 0278-4343.
Titre du document
Spatial and temporal variability of hydrodynamics on the Amazon Continental Shelf : an observational approach
Année de publication
2025
Auteurs
de Freitas P. P., Cirano M., Teixeira C. E. P., Melres S. J. R., de Sousa Akcd, Gomes V. J. C., Guerrero-Martin C. A., Koch Larrouy Ariane
Source
Continental Shelf Research, 2025,
291, p. 105491 [17 p.] ISSN 0278-4343
Amazon Continental Shelf (ACS) presents highly energetic hydrodynamics, modulated by multiple forcing mechanisms, and significant socio-economic and climate importance. This study characterizes the spatial-temporal variability of hydrodynamics on the ACS between 2 degrees S and 4 degrees N based on in situ data of 6 coastal sea level stations provided by IBGE, BNDO and SiMCosta, velocity measurements from 201 drifters of NOAA Global Drifter Program and 3 moorings of the AMANDES III project, and 127 CTD profiles from AMANDES and REVIZEE projects. The analysis of the coastal sea level shows that the tidal band contributes for 95 % (Santana, Amapà shelf) to 99 % (Turiaçu and Ribamar, Maranhão shelf) of the temporal variability of the sea level. Moreover, it shows that characteristics typical of a macrotidal regime occur up to 75 % and 41 % of the time at Turiaçu and Salinópolis, the eastern and central regions of the ACS, respectively. Velocity time series from drifters and moorings reveal a northwestward flow pattern along the ACS, which is associated with wind-driven circulation. The semidiurnal tides play a crucial role in the temporal variability of the cross-shelf velocity component, reaching a maximum percentage importance of 90 % on the central region of the ACS. Residual currents (without tides) are more pronounced in the alongshelf component. Their percentage importance increases towards the western shelf, from 68 % (73 %) and 20 % (10 %) in the upper (lower) water column at the eastern shelf, to 95 % (90 %) and 54 % (46 %) in the alongshelf and cross-shelf components, respectively. The wavelet analysis of the residual currents reveals high energy in two distinct period bands between 4 and 20 days and longer than 20 days at all moorings. The first period band is associated with wind modulations, while the second band indicates influence of the North Brazil Current (NBC) fluctuations. The time series of Richardson numbers show that the central and western shelves are stable for most of the time (>70 %). The stratification (N2) and vertical velocity shear (S2) parameters increase toward MAM4 (western shelf) associated with the spreading of the Amazon River plume and the increased influence of the NBC on the speed and direction of currents in the outer shelf. The TS diagrams show the presence of three distinct water masses on the ACS: coastal water influenced by river discharge, mixed water, and oceanic water.
Plan de classement
Limnologie physique / Océanographie physique [032]
;
Hydrologie [062]
Description Géographique
BRESIL ; ATLANTIQUE ; AMAZONE COURS D'EAU
Localisation
Fonds IRD [F B010093601]
Identifiant IRD
fdi:010093601
