Browsing by Author "Guyot, J. L."
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Item Open Access Cuantificación de la producción de sedimentos fluviales en suspensión, transportados desde los Andes hacia los manglares de Tumbes y Zarumilla(Instituto Geofísico del Perú, 2013-08) Morera Julca, Sergio Byron; Espinoza, Jhan Carlo; Takahashi, Ken; Atoche, D.; Guyot, J. L.; Yerren, J.; Condom, T.Los manglares en el norte del Perú se encuentran concentrados principalmente en la desembocadura de la cuenca binacional Puyango-Tumbes (Perú y Ecuador) y la cuenca Zarumilla. El presente estudio cuantificó y caracterizó la producción de sedimentos (SY) en ambas cuencas tropicales; basándose en información de la estación hidrosedimentológica El Tigre que delimita 4708 km2 (entre 22 y 3875 msnm) y la estación Palmales, que monitorea 639 km2 (entre 42 y 1242 msnm) de la cuenca Zarumilla. La campaña de monitoreo a una alta frecuencia en la cuenca de Zarumilla mostro una alta correlación entre la el caudal sólido y líquido instantáneo. Por otra parte el análisis de la base de datos en la estación El Tigre permitió la construcción de las curvas de gasto líquido (Q) y sólido (Qs). La cuantificación de la SY para los años observados (2004-2012) fluctúa entre 0.47x106 y 9.5x106 t.año-1 , encontrándose un promedio multianual de 1.6x106 t.año-1. El caudal sólido específico (SSY) promedio es 340 t.km-2 .año-1 , del cual el 92% va a ser transportado durante el periodo de lluvias (Ene-Abr), 7% durante transición (May-Jun, Nov-Dic) y solo1% durante el estiaje (Jul-Oct). A ello podemos agregar que durante años normales el 38% del SSY es transportado por caudales entre 300 a 500 m3 .s-1. Finalmente, se estimó el caudal sólido para el periodo 1963-2004 a partir de la curva de gasto sólido (Qs=F(Q)); los resultados muestran que para escenarios similares a los mega Niños del 1982-83 y 1997-98 la SY podría fluctuar entre 5400 a 9721 t.km-2 .año-1 respectivamente (entre 16 y 29 veces más que un año normal), dichas cifras marcarían una de las tasas de erosión más críticas a nivel mundial.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 Future changes in precipitation and impacts on extreme streamflow over Amazonian sub-basins(IOP Publishing, 2013-03-07) Guimberteau, M.; Ronchail, J.; Espinoza, Jhan Carlo; Lengaigne, M.; Sultan, B.; Polcher, J.; Drapeau, G.; Guyot, J. L.; Ducharne, A.; Ciais, P.Because of climate change, much attention is drawn to the Amazon River basin, whose hydrology has already been strongly affected by extreme events during the past 20 years. Hydrological annual extreme variations (i.e. low/high flows) associated with precipitation (and evapotranspiration) changes are investigated over the Amazon River sub-basins using the land surface model ORCHIDEE and a multimodel approach. Climate change scenarios from up to eight AR4 Global Climate Models based on three emission scenarios were used to build future hydrological projections in the region, for two periods of the 21st century. For the middle of the century under the SRESA1B scenario, no change is found in high flow on the main stem of the Amazon River (Obidos station), but a systematic discharge decrease is simulated during the recession period, leading to a 10% low-flow decrease. Contrasting discharge variations are pointed out depending on the location in the basin. In the western upper part of the basin, which undergoes an annual persistent increase in precipitation, high flow shows a 7% relative increase for the middle of the 21st century and the signal is enhanced for the end of the century (12%). By contrast, simulated precipitation decreases during the dry seasons over the southern, eastern and northern parts of the basin lead to significant low-flow decrease at several stations, especially in the Xingu River, where it reaches −50%, associated with a 9% reduction in the runoff coefficient. A 18% high-flow decrease is also found in this river. In the north, the low-flow decrease becomes higher toward the east: a 55% significant decrease in the eastern Branco River is associated with a 13% reduction in the runoff coefficient. The estimation of the streamflow elasticity to precipitation indicates that southern sub-basins (except for the mountainous Beni River), that have low runoff coefficients, will become more responsive to precipitation change (with a 5 to near 35% increase in elasticity) than the western sub-basins, experiencing high runoff coefficient and no change in streamflow elasticity to precipitation. These projections raise important issues for populations living near the rivers whose activity is regulated by the present annual cycle of waters. The question of their adaptability has already arisen.Item Restricted Holocene changes in monsoon precipitation in the Andes of NE Peru based on δ¹⁸O speleothem records(Elsevier, 2016-08-15) Bustamante, M. G.; Cruz, F. W.; Vuille, M.; Apaéstegui Campos, James Emiliano; Strikis, N.; Panizo, G.; Novello, F. V.; Deininger, M.; Sifeddine, A.; Cheng, H.; Moquet, J. S.; Guyot, J. L.; Santos, R. V.; Segura Cajachagua, Hans Mikhail; Edwards, R. L.Two well-dated δ¹⁸O-speleothem records from Shatuca cave, situated on the northeastern flank of the Peruvian Andes (1960 m asl) were used to reconstruct high-resolution changes in precipitation during the Holocene in the South American Summer Monsoon region (SASM). The records show that precipitation increased gradually throughout the Holocene in parallel with the austral summer insolation trend modulated by the precession cycle. Additionally the Shatuca speleothem record shows several hydroclimatic changes on both longer- and shorter-term time scales, some of which have not been described in previous paleoclimatic reconstructions from the Andean region. Such climate episodes, marked by negative excursions in the Shatuca δ¹⁸O record were logged at 9.7–9.5, 9.2, 8.4, 8.1, 5.0, 4.1, 3.5, 3.0, 2.5, 2.1 and 1.5 ka b2k, and related to abrupt multi-decadal events in the SASM. Some of these events were likely associated with changes in sea surface temperatures (SST) during Bond events in the North Atlantic region. On longer time scales, the low δ¹⁸O values reported between 5.1-5.0, 3.5–3.0 and 1.5 ka b2k were contemporaneous with periods of increased sediment influx at Lake Pallcacocha in the Andes of Ecuador, suggesting that the late Holocene intensification of the monsoon recorded at Shatuca site may also have affected high altitudes of the equatorial Andes further north. Numerous episodes of low SASM intensity (dry events) were recorded by the Shatuca record during the Holocene, in particular at 10.2, 9.8, 9.3, 6.5, 5.1, 4.9, 2.5 and 2.3 ka b2k, some of them were synchronous with dry periods in previous Andean records.Item Open Access Hydroclimate variability of the northwestern Amazon Basin near the Andean foothills of Peru related to the South American Monsoon System during the last 1600 years(European Geosciences Union (EGU), 2014-11-19) Apaéstegui Campos, James Emiliano; Cruz, F. W.; Sifeddine, A.; Vuille, M.; Espinoza, Jhan Carlo; Guyot, J. L.; Khodri, M.; Strikis, N.; Santos, R. V.; Cheng, H.; Edwards, L.; Carvalho, E.; Santini, W.In this paper we explore a speleothem δ ¹⁸O record from Palestina cave, northwestern Peru, at a site on the eastern side of the Andes cordillera, in the upper Amazon Basin. The δ ¹⁸O record is interpreted as a proxy for South American Summer Monsoon (SASM) intensity and allows the reconstruction of its variability during the last 1600 years. Two periods of anomalous changes in the climate mean state corresponding to the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA) periods identified in the Northern Hemisphere are recognized in the record, in which decreased and increased SASM activity, respectively, have been documented. Variations in SASM activity between the MCA and the LIA seem to be larger over the northern part of the continent, suggesting a latitudinal dependence of the MCA footprint. Our results, based on time series, composite and wavelet analyses, suggest that the Atlantic Multidecadal Oscillation (AMO) plays an relevant role for SASM modulation on multidecadal scales (∼ 65 years), especially during dry periods such as the MCA. Composite analyses, applied to evaluate the influence of the AMO on the Palestina cave δ¹⁸O and other δ¹⁸O-derived SASM reconstructions, allow insight into the spatial footprints of the AMO over tropical South America and highlight differences between records during key studied periods. This work also reveals that replicating regional climate signals from different sites, and using different proxies is absolutely essential for a comprehensive understanding of past changes in SASM activity.Item Open Access Hydroclimate variability of the northwestern Amazon Basin near the Andean foothills of Peru related to the South American Monsoon System during the last 1600 years(European Geosciences Union (EGU), 2014) Apaéstegui Campos, James Emiliano; Cruz, F. W.; Sifeddine, A.; Vuille, M.; Espinoza, Jhan Carlo; Guyot, J. L.; Khodri, M.; Strikis, N.; Santos, R. V.; Cheng, H.; Edwards, L.; Carvalho, E.; Santini, W.In this paper we explore a speleothem δ¹⁸O record from Palestina Cave, North Eastern Peru, at a site on the eastern side of the Andes cordillera, upper Amazon Basin, interpreted as a proxy for South America Summer Monsoon (SASM) intensity. This record 5 allows reconstructing SASM activity with ∼ 5 yr time resolution over the last 1600 yr, spanning two major periods of climate variability: the Medieval Climate Anomaly (MCA; 900–1200 AD) and Little Ice Age (LIA 1400–1850 AD) recognized as periods of decrease and increase SASM activity respectively. Time series and wavelet analyses reveal decadal to multidecadal frequencies. Our results suggest that Atlantic Multi10 decadal Oscillation mode (AMO) plays an important role for SASM modulation on multidecadal scale (∼ 65 yr), especially over dry periods such as observed during MCA. Frequencies of 8 and 25 yr simultaneously with multidecadal signal (65 yr) are found over the LIA. and suggest that those modes could be related to North Atlantic Oscillation (NAO) and Interdecadal Pacific Oscillation mode (IPO). Comparison with other 15 South American Paleoprecipitation records shows that the Atlantic and Pacific decadal to multidecadal variability and their teleconnections play an important role in the intensity and the regional patterns of rainfall distribution during the last 1600 yr.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.