Intensification of the Amazon hydrological cycle over the last two decades

Reproduced with permission of the publisher. Online Open article. © 2013 American Geophysical UnionThe Amazon basin hosts half the planet's remaining moist tropical forests, but they may be threatened in a warming world. Nevertheless, climate model predictions vary from rapid drying to modest wetting. Here we report that the catchment of the world's largest river is experiencing a substantial wetting trend since approximately 1990. This intensification of the hydrological cycle is concentrated overwhelmingly in the wet season driving progressively greater differences in Amazon peak and minimum flows. The onset of the trend coincides with the onset of an upward trend in tropical Atlantic sea surface temperatures (SST). This positive longer-term correlation contrasts with the short-term, negative response of basin-wide precipitation to positive anomalies in tropical North Atlantic SST, which are driven by temporary shifts in the intertropical convergence zone position. We propose that the Amazon precipitation changes since 1990 are instead related to increasing atmospheric water vapor import from the warming tropical Atlantic

Genetic diversity of a large set of horse breeds raised in France assessed by microsatellite polymorphism

After the recent publication of our article (Leroy, Genetics Selection Evolution 2009 41:5), we found several errors in the published Table Three, concerning the computation of contribution to within-breed diversity (CW). We apologize to the readers for these errors, which are corrected in the present erratum

Variação espacial de cátions, ânions e variáveis físico-químicas no rio Solimões-Amazonas entre Manaus e Jutaí, bacia amazônica

Cátions e ânions majoritários são espécies químicas de grande importância nos diversos compartimentos aquáticos, porém, pouco abordados de forma exclusiva na bacia amazônica. Neste sentido, o objetivo deste estudo foi avaliar a dinâmica espacial de Na+, Ca2+, K+, Mg2+, Cl- e SO4 2- em um trecho do rio Solimões-Amazonas, levando-se em consideração a alcalinidade, potencial hidrogeniônico (pH), condutividade elétrica (CE), sólidos totais em suspensão (STS) e carbono orgânico total (COT). As coletas foram realizadas em maio, julho e setembro de 2012 em sete pontos na calha principal do rio Solimões-Amazonas e na foz de alguns dos principais tributários: rios Jutaí, Juruá, Japurá e Purus. Os cátions e ânions foram analisados por cromatografia de íons, STS por gravimetria, pH por potenciometria, alcalinidade por titulação potenciométrica, CE por condutimetria e o COT por oxidação catalítica por combustão. As concentrações médias dos cátions seguiram esta ordem Ca2+>Na+>Mg2+>K+ e dos ânions SO4 2->Cl-. De montante à jusante a tendência foi diminuição nas concentrações de cátions e ânions, das variáveis pH, CE, STS e alcalinidade, além do aumento das concentrações de COT. O presente estudo evidenciou mudanças nas características químicas sofridas pelo rio Solimões em seu curso. O aporte dos tributários pode ser apontado como um dos fatores responsáveis por essas modificações

Oscillations journalieres de la profondeur des nappes en l'absence de precipitations

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Détermination de l'altitude du Zéro des stations hydrométriques en Amazonie brésilienne. Application aux lignes d'eau des Rios Negro, Solimões et Amazone

Le rattachement altimétrique d'une station hydrométrique à un repère du Nivellement Général est habituellement effectué dans le but de connaître, lorsqu'il y a plusieurs stations, la pente de la ligne d'eau. Jusqu'à la fin de la décennie 2000, les stations hydrométriques amazoniennes n'étaient pas rattachées car le manque de réseau routier était un obstacle majeur au classique nivellement direct. Mais la fin de cette décennie a vu l'expansion de l'altimétrie satellitaire, et plus particulièrement celle de la méthode utilisant le GPS associé à l'utilisation du modèle de géoïde EGM08. Cette nouvelle technique est particulièrement précieuse pour niveler les stations hydrométriques du bassin amazonien. Nous avons traité ici les stations hydrométriques de l'Amazone depuis son embouchure jusqu'à la frontière Brésil/Pérou et celles des rios Negro et Solimões pour leurs parties brésiliennes. Les pentes moyennes de ces différents biefs décroissent normalement sur le Rio Solimões et l'Amazone, tandis que le bief Moura-Manaus, sur le Rio Negro, présente anormalement une pente très faible (6 mm*km‑1) au risque de provoquer des inversions d'écoulement. Le Bas Amazone est raccordé à l'altitude donnée par la trace de l'orbite 202 des satellites Topex-Poseidon et Jason-1 mais malheureusement nous ne disposons que d'une seule année de relevés limnigraphiques sur ce tronçon. Les comparaisons des pentes de la ligne d'eau avec d'autres fleuves (Volga, Danube, Nil, Mississipi et Rhin) indiquent que la pente de l'Amazone est, avec en moyenne 21 mm*km‑1 de Tabatinga (frontière Brésil/Pérou) à l'Océan Atlantique (soit sur 3 000 km) deux fois moindre que celle de la Volga (qui présente la ligne d'eau de pente la plus faible sur les cinq fleuves étudiés). Ceci, associé au fait que le fond du lit de l'Amazone est, sur 2 000 km à partir de son embouchure, à une quarantaine de mètres en-dessous du niveau de l'océan, nous conduirait à penser que l'écoulement du fleuve subit une poussée des eaux amont, issues de la Cordillère des Andes. $EN$The altimetric relation of a hydrometric station to the General Levelling mark is usually performed in order to know, when there are several stations, the slope of the water line. Until the end of the 2000s, Amazonian hydrometric stations were not related because the lack of roads was a major obstacle to classical direct levelling. However, the end of this decade has seen the expansion of satellite altimetry and more particularly the development of the method using GPS (Global Positioning System) associated with the use of the geoid model EGM08. This new technique is particularly valuable for level gauging stations in the Amazon Basin. Here we have treated hydrometric stations of the Amazon from its mouth to the Brazil/Peru border and those of the rivers Negro and Solimões in their Brazilian part. Average slopes of these reaches decrease normally for the Rios Solimões and Amazon, whereas for the Moura/Manaus reach on the Rio Negro, the abnormally low slope (6 mm*km‑1) may cause inverted flow. The lower Amazon is connected to the altitude given by the trace of orbit 202 of the Topex-Poseidon and Jason-1 satellites, but unfortunately we only have one year of gauging readings for this reach. Comparisons of the water slopes with other rivers (Volga, Danube, Nile, Mississippi and Rhine) indicate that the slope of the Amazon is, with an average of 21 mm*km‑1 from Tabatinga (Brazil/Peru border) to the Atlantic Ocean (a distance of 3000 km), two times less than that of the Volga (which has the lowest water line slope among the five rivers studied). This, coupled with the fact that the bed of the Amazon is, for about 2000 km from its mouth, about forty meters below the level of the ocean, would lead us to believe that the river's flow is propelled by water arriving from upstream, from the Andes