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Frank N.,Institute Pierre Simon Laplace LSCE IPSL | Freiwald A.,Senckenberg Institute | Freiwald A.,Friedrich - Alexander - University, Erlangen - Nuremberg | Lopez Correa M.,Friedrich - Alexander - University, Erlangen - Nuremberg | And 14 more authors.
Geology | Year: 2011

U-series age patterns obtained on reef framework-forming cold-water corals collected over a nearly 6000-km-long continental margin sector, extending from off Mauritania (17°N; northwest Africa) to the southwestern Barents Sea (70°N; northeastern Europe), reveal strong climate infl uences on the geographical distribution and sustained development of these ecosystems. Over the past three glacial-interglacial cycles, framework-forming cold-water corals (Lophelia pertusa and Madrepora oculata) seem to have predominantly populated reefs, canyons, and patches in the temperate East Atlantic and the Mediterranean Sea. Above 50°N corals colonize reefs in the northern East Atlantic primarily during warm climate periods with the biogeographic limit advancing from ~50°N to ~70°N. We propose that north-south oscillations of the biogeographic limit of reef developments are paced by ice ages and may occur synchronously with north-south displacement of cold nutrient-rich intermediate waters and surface productivity related to changes of the polar front. © 2011 Geological Society of America.

Berg A.,Institute Pierre Simon Laplace LOCEAN IPSL | Berg A.,Institute Pierre Simon Laplace LSCE IPSL | Berg A.,University Pierre and Marie Curie | Sultan B.,Institute Pierre Simon Laplace LOCEAN IPSL | de Noblet-Ducoudre N.,Institute Pierre Simon Laplace LSCE IPSL
Climatic Change | Year: 2011

Studying the large-scale relationships between climate and agriculture raises two different issues: the impact of climate on crops, and the potential feedbacks to climate from croplands. A relevant and consistent framework to address this twofold issue is to extend existing Dynamic Global Vegetation Models, which can be coupled to climate models, in order to explicitly account for croplands. Here we present the first results of such a strategy applied to tropical croplands over West Africa. We introduce into the terrestrial biosphere model ORCHIDEE (IPSL) adequate processes and parameterisations taken from the crop model SARRAH (CIRAD), which is calibrated for millet over this region. The resulting model, ORCH-mil, realistically simulates the growth and yield of millet when tested on an experimental station in Senegal. The model is then applied over West Africa using a 36-year climate reanalysis dataset. First the model is tested in terms of yield simulation, against national millet yields from the FAO database. The ability of the model to reproduce the spatial and temporal variability of millet yields is assessed. Then, the effects on land surface fluxes of explicitly accounting for croplands are examined: significant differences between ORCH-mil and ORCHIDEE appear, through changes in sensible and latent heat fluxes, surface albedo, and water resources. These differences encompass a potential impact on the monsoon system, mainly during the retreat of monsoon rains. © 2010 Springer Science+Business Media B.V.

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