Browsing by Author "Moquet, Jean Sébastien"
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Item Restricted A reassessment of the suspended sediment load in the Madeira River basin from the Andes of Peru and Bolivia to the Amazon River in Brazil, based on 10 years of data from the HYBAM monitoring programme(Elsevier, 2017-10) Vauchel, Phillippe; Santini, William; Guyot, Jean Loup; Moquet, Jean Sébastien; Martínez, Jean Michel; Espinoza, Jhan Carlo; Baby, Patrice; Fuertes, Oscar; Noriega, Luis; Puita, Oscar; Sondag, Francis; Fraizy, Pascal; Armijos Cardenas, Elisa Natalia; Cochonneau, Gérard; Timouk, Franck; Olivera, Eurides de; Filizola, Naziano; Molina, Jorge; Ronchail, JosyaneThe Madeira River is the second largest tributary of the Amazon River. It contributes approximately 13% of the Amazon River flow and it may contribute up to 50% of its sediment discharge to the Atlantic Ocean. Until now, the suspended sediment load of the Madeira River was not well known and was estimated in a broad range from 240 to 715 Mt yr⁻¹. Since 2002, the HYBAM international network developed a new monitoring programme specially designed to provide more reliable data than in previous intents. It is based on the continuous monitoring of a set of 11 gauging stations in the Madeira River watershed from the Andes piedmont to the confluence with the Amazon River, and discrete sampling of the suspended sediment concentration every 7 or 10 days. This paper presents the results of the suspended sediment data obtained in the Madeira drainage basin during 2002–2011. The Madeira River suspended sediment load is estimated at 430 Mt yr⁻¹ near its confluence with the Amazon River. The average production of the Madeira River Andean catchment is estimated at 640 Mt yr⁻¹ (±30%), the corresponding sediment yield for the Andes is estimated at 3000 t km⁻² yr⁻¹ (±30%), and the average denudation rate is estimated at 1.20 mm yr⁻¹ (±30%). Contrary to previous results that had mentioned high sedimentation rates in the Beni River floodplain, we detected no measurable sedimentation process in this part of the basin. On the Mamoré River basin, we observed heavy sediment deposition of approximately 210 Mt yr⁻¹ that seem to confirm previous studies. But while these studies mentioned heavy sedimentation in the floodplain, we showed that sediment deposition occurred mainly in the Andean piedmont and immediate foreland in rivers (Parapeti, Grande, Pirai, Yapacani, Chimoré, Chaparé, Secure, Maniqui) with discharges that are not sufficiently large to transport their sediment load downstream in the lowlands.Item Restricted Calibration of speleothem δ¹⁸O records against hydroclimate instrumental records in Central Brazil(Elsevier, 2016-04) Moquet, Jean Sébastien; Cruz, F. W.; Novello, V. F.; Stríkis, N. M.; Deininger, M.; Karmann, I.; Ventura Santos, R.; Millo, C.; Apaéstegui Campos, James Emiliano; Guyot, J.-L.; Siffedine, A.; Vuille, M.; Cheng, H.; Edwards, R. L.; Santini, W.δ¹⁸O in speleothems is a powerful proxy for reconstruction of precipitation patterns in tropical and sub-tropical regions. The aim of this study is to calibrate the δ¹⁸O record of speleothems against historical precipitation and river discharge data in central Brazil, a region directly influenced by the Southern Atlantic Convergence Zone (SACZ), a major feature of the South American Monsoon System (SAMS). The present work is based on a sub-annual resolution speleothem record covering the last 141 years (the period between the years 1870 and 2011) from a cave in central Brazil. The comparison of this record with instrumental hydroclimate records since 1921 allows defining a strong relationship between precipitation variability and stable oxygen isotope ratios from speleothems. The results from a monitoring program of climatic parameters and isotopic composition of rainfall and cave seepage waters performed in the same cave, show that the rain δ¹⁸O variability is dominated by the amount effect in this region, while δ¹⁸O drip water remains almost constant over the monitored period (1.5 years). The δ¹⁸O of modern calcite, on the other hand, shows clear seasonal variations, with more negative values observed during the rainy season, which implies that other factors also influence the isotopic composition of carbonate. However, the relationship between δ¹⁸O of carbonate deposits and rainwater is supported by the results from the comparison between speleothem δ18O records and historical hydroclimate records. A significant correlation between speleothem δ¹⁸O and monsoon rainfall variability is observed on sub-decadal time scales, especially for the monsoon period (DJFM and NDJFM), once the rainfall record have been smoothed with a 7–9 years running mean. This study confirms that speleothem δ¹⁸O is directly associated with monsoon rainfall variability in central Brazil. The relationship between speleothem δ¹⁸O records and hydroclimatic historical records allows approximation of the absolute changes in mean annual rainfall during the last millennia in the SACZ/SAMS domain.Item Restricted Climate control on silicate weathering and physical erosion rates in young orogenic belts: Case study along a runoff gradient in Pacific and Amazonian Andean basins based on SNO-HYBAM Monitoring Program data(EGU General Assembly, 2017-04) Moquet, Jean Sébastien; Guyot, Jean-Loup; Viers, Jérôme; Crave, Alain; Morera Julca, Sergio Byron; Rau, Pedro; Armijos Cardenas, Elisa Natalia; Lagane, Christelle; Lavado Casimiro, Waldo Sven; Pombosa, Rodrigo; Fraizy, Pascal; Santini, William; Timouk, Franck; Vauchel, Philippe; Martinez, Jean-MichelAt the global scale and on geological time scales, mechanical erosion and chemical weathering budgets are linked. Together, these processes contribute to the formation and the degradation of the Earth's critical zone and to the biogeochemical cycles of elements. In young orogenic belts, climate and tectonic subsidence control together the rate of these matter balance budget and their relationships. The climate gradient observed along the Andean basin in both the Pacific and the Atlantic slopes offers the opportunity to explore the role of the climate variability on the erosion and weathering budgets and on their reciprocal relationships. Based on the SNO-HYBAM Monitoring Program database (Geodynamical, hydrological and Biogeochemical control of erosion/weathering and material transport in the Amazon, Orinoco and Congo basins), we explore the relationship between climate, the lithology, silicate weathering rates and physical erosion rates along a runoff gradient in Andean basins of the Amazon River (13 gauging stations) and Pacific drainage rivers (5 gauging stations). No homogenous relationship between erosion rates (E) and chemical weathering rate (W) is observed over the monitored basins. Only the volcanic basins respond to a global relationship defined in the literature while the other basins budget may depend on anthropogenic interferences on erosion/sedimentation budget, a lithology dependence of the W-E relationship parameters or/and on the existence of a threshold in this relationship. The results presented here contribute to better understanding the role of mountains belt formation in the biogeochemical cycles and in particular in the long-term carbon cycle.Your presentation type preference.Item Restricted River mixing in the Amazon as a driver of concentration‐discharge relationships(American Geophysical Union (AGU), 2017-11) Bouchez, Julien; Moquet, Jean Sébastien; Espinoza, Jhan Carlo; Martinez, Jean‐Michel; Guyot, Jean‐Loup; Lagane, Christelle; Filizola, Naziano; Noriega, Luis; Hidalgo Sánchez, Liz; Pombosa, RodrigoLarge hydrological systems aggregate compositionally different waters derived from a variety of pathways. In the case of continental‐scale rivers, such aggregation occurs noticeably at confluences between tributaries. Here we explore how such aggregation can affect solute concentration‐discharge (C‐Q) relationships and thus obscure the message carried by these relationships in terms of weathering properties of the Critical Zone. We build up a simple model for tributary mixing to predict the behavior of C‐Q relationships during aggregation. We test a set of predictions made in the context of the largest world's river, the Amazon. In particular, we predict that the C‐Q relationships of the rivers draining heterogeneous catchments should be the most “dilutional” and should display the widest hysteresis loops. To check these predictions, we compute 10 day‐periodicity time series of Q and major solute (Si, Ca²⁺, Mg²⁺, K⁺, Na⁺, Cl‐, urn:x-wiley:00431397:media:wrcr22891:wrcr22891-math-0001) C and fluxes (F) for 13 gauging stations located throughout the Amazon basin. In agreement with the model predictions, C‐Q relationships of most solutes shift from a fairly “chemostatic” behavior (nearly constant C) at the Andean mountain front and in pure lowland areas, to more “dilutional” patterns (negative C‐Q relationship) toward the system mouth. More prominent C‐Q hysteresis loops are also observed at the most downstream stations. Altogether, this study suggests that mixing of water and solutes between different flowpaths exerts a strong control on C‐Q relationships of large‐scale hydrological systems.Item Open Access Sediment budget in the Ucayali river basin, an Andean tributary of the Amazon river(Copernicus Publications, 2015-03-03) Santini, William; Martínez, Jean-Michel; Espinoza Villar, Raúl Arnaldo; Cochonneau, Gerard; Vauchel, Philippe; Moquet, Jean Sébastien; Baby, Patrice; Espinoza, Jhan Carlo; Lavado, Waldo; Carranza, Jorge; Guyot, Jean-LoupFormation of mountain ranges results from complex coupling between lithospheric deformation, mechanisms linked to subduction and surface processes: weathering, erosion, and climate. Today, erosion of the eastern Andean cordillera and sub-Andean foothills supplies over 99% of the sediment load passing through the Amazon Basin. Denudation rates in the upper Ucayali basin are rapid, favoured by a marked seasonality in this region and extreme precipitation cells above sedimentary strata, uplifted during Neogene times by a still active sub-Andean tectonic thrust. Around 40% of those sediments are trapped in the Ucayali retro-foreland basin system. Recent advances in remote sensing for Amazonian large rivers now allow us to complete the ground hydrological data. In this work, we propose a first estimation of the erosion and sedimentation budget of the Ucayali River catchment, based on spatial and conventional HYBAM Observatory network.Item Restricted Temporal variability and annual budget of inorganic dissolved matter in Andean Pacific Rivers located along a climate gradient from northern Ecuador to southern Peru(Elsevier, 2018) Moquet, Jean Sébastien; Guyot, Jean-Loup; Morera Julca, Sergio Byron; Crave, Alain; Rau, Pedro; Vauchel, Philippe; Lagane, Christelle; Sondag, Francis; Lavado, Casimiro Waldo; Pombosa, Rodrigo; Martinez, Jean-MichelIn Ecuador and Peru, geochemical information from Pacific coastal rivers is limited and scarce. Here, we present an unedited database of major element concentrations from five HYBAM observatory stations monitored monthly between 4 and 10 years, and the discrete sampling of 23 Andean rivers distributed along the climate gradient of the Ecuadorian and Peruvian Pacific coasts. Concentration (C) vs. discharge (Q) relationships of the five monitored basins exhibit a clear dilution behavior for evaporites and/or pyrite solutes, while the solute concentrations delivered by other endmembers are less variable. Spatially, the annual specific fluxes for total dissolved solids (TDS), Ca²⁺, HCO₃, K+, Mg²⁺, and SiO₂ are controlled on the first order by runoff variability, while Cl, Na⁺ and SO₄² are controlled by the occurrence of evaporites and/or pyrite. The entire Pacific basin in Ecuador and Peru exported 30 Mt TDS·yr ¹, according to a specific flux of ∼70 t·km ²·yr ¹. This show that, even under low rainfall conditions, this orogenic context is more active, in terms of solute production, than the global average.