Browsing by Author "Cochonneau, G."
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Item Restricted Fluctuations in the monthly discharge of Guyana Shield rivers, related to Pacific and Atlantic climate variability(Taylor & Francis, 2012-06) Labat, D.; Espinoza, Jhan Carlo; Ronchail, J.; Cochonneau, G.; De Oliveira, E.; Doudou, J. C.; Guyot, J. L.The discharge variability of the main rivers that drain the Guyana Shield is analysed over the last 50 years using cross-wavelet, coherence and composite analysis involving oceanic and atmospheric variables. We highlight the overall hydro-climatological homogeneity of this region that allowed us to focus on the longest discharge time series available. Therefore, a wavelet cross-analysis was carried out between monthly and seasonal Maroni River discharge at the Langa Tabiki station and selected climate indices. This confirms a strong relationship between the hydrology of the Guyana Shield and the Pacific sea-surface temperature (SST) fluctuations. There is evidence of intermittent influence, of between inter-annual and near decadal scales, of the Atlantic SST fluctuations, in particular around 1970 and 1990. Finally, we show that the links between oceanic regions and high discharge in the rivers of Guyana are realized through the reinforcement of the Walker and Hadley cells between the Amazon and the adjacent oceans and through decreased trade winds and monsoon flux that favour the persistence of humidity over the Guyana Shield.Item Open Access Rainfall control on Amazon sediment flux: synthesis from 20 years of monitoring(IOP Publishing, 2020-05-14) Armijos Cardenas, Elisa Natalia; Crave, A.; Espinoza, Jhan Carlo; Filizola, N.; Espinoza-Villar, R.; Ayes, I.; Fonseca, P.; Fraizy, P.; Gutierrez, O.; Vauchel, P.; Camenen, B.; Martiınez, J. M.; Dos Santos, A.; Santini, W.; Cochonneau, G.; Guyot, J. L.The biodiversity and productivity of the Amazon floodplain depend on nutrients and organic matter transported with suspended sediments. Nevertheless, there are still fundamental unknowns about how hydrological and rainfall variability influence sediment flux in the Amazon River. To address this gap, we analyzed 3069 sediment samples collected every 10 days during 1995–2014 at five gauging stations located in the main rivers. We have two distinct fractions of suspended sediments, fine (clay and silt) and coarse (sand), which followed contrasting seasonal and long-term patterns. By taking these dynamics into account, it was estimated, for first time, in the Amazon plain, that the suspended sediment flux separately measured approximately 60% fine and 40% coarse sediment. We find that the fine suspended sediments flux is linked to rainfall and higher coarse suspended sediment flux is related with discharge. Additionally this work presents the time lag between rainfall and discharge, which is related to the upstream area of the gauging. This result is an important contribution to knowledge of biological and geomorphological issues in Amazon basin.