Past changes in riverine input and ocean circulation in the Gulf of Guinea

Large river systems draining the West African Monsoon area deliver sediments and dissolved trace elements into the Gulf of Guinea (GoG) in the easternmost equatorial Atlantic. The different catchment areas of these river systems are characterized by different geological ages and rock types releasing distinct radiogenic neodymium isotope compositions during weathering which are supplied to the GoG. The main rivers discharging into the GoG are the Niger, the Sanaga, the Nyong and the Ntem with present day εNd signatures of -10.5 [1], -12.3, -12.5 and -28.1 [2], respectively. These riverine inputs mix with the tropical Atlantic surface waters. At intermediate water depths Antarctic Intermediate Water (AAIW) prevails whereas the deep basin at this location is mainly filled with NADW. We focus on a marine sediment core that was recovered off the Sanaga and Ntem Rivers and we reconstruct changes in riverine inputs and in mixing of surface and deep water masses over the past 140,000 years. Changes in riverine inputs most likely reflecting latitudinal shifts of the rainfall zones across the different catchment areas were obtained from the Nd isotope signatures of the residual detrital fraction of the sediment. Sediment leachates of several GoG core top samples reflect the riverine input from nearby rivers indicating transport of particles coated in the rivers. Both the sediment leachates and the residual detrital fraction show similar patterns, with shifts towards radiogenic values during the interglacials and least radiogenic values during glacial periods. This shift in εNd values may be attributed to the migration of the rainfall zones towards the north during interglacial times and thus implies the increased influence of the northern rivers, the Sanaga and Nyong. The oxidatively-reductively cleaned planktonic foraminiferal calcite of the core top samples in the GoG reflects surface seawater signatures. Non-reductively cleaned planktonic foraminiferal tests and cleaned shallow endo-benthic and epi-benthic foraminiferal tests were used to acquire information about past bottom waters. Difficulties in cleaning down core foraminiferal samples were experienced and these samples appear to be contaminated by secondary manganese and iron bearing phases, even after cleaning. Those phases may have overprinted the original surface water Nd isotope composition in the planktonic foraminiferal tests. As the planktonic and benthic foraminiferal values are overall similar to the sediment leachates, the foraminiferal isotope signatures are most likely overprinted by isotopic signals originating from the rivers due to remobilization processes in the sediments and formation of secondary phases such as Mn-carbonates, which are attached to the foraminiferal calcites. References: [1] Goldstein et al. (1984) Earth and Planetary Science Letter 70, 221-236. [2] Weldeab et al. (2011) Geophysical Research Letter 38, pp. 5

Innovation in natural resource management

International agricultural research is expanding beyond the development of annual crop technologies for individual farms to the development of longer-tern natural resource management techniques for entire landscapes. But technologies of practices with a long lag time between investment and returns are unlikely to be adopted by farmers unless they have secure rights to the underlying resources (property rights). Similarly, technologies that span multiple farms are unlikely to be adopted unless neighbors and groups work together (collective action). But little is know about the way property rights and collective action in developing countries mediate the adoption of technologies by farmers and groups. This statement offers suggestions for promoting sustainable natural resource management.

The Evolution of Hetergeneous "Clumpy Jets": A Parameter Study

We investigate the role discrete clumps embedded in an astrophysical jet play on the jet's morphology and line emission characteristics. By varying clumps' size, density, position, and velocity, we cover a range of parameter space motivated by observations of objects such as the Herbig Haro object HH~34. We here extend the results presented in Yirak et al. 2009, including how analysis of individual observations may lead to spurious sinusoidal variation whose parameters vary widely over time, owing chiefly to interacts between clumps. The goodness of the fits, while poor in all simulations, are best when clump-clump collisions are minimal. Our results indicate that a large velocity dispersion leads to a clump-clump collision-dominated flow which disrupts the jet beam. Finally, we present synthetic emission images of H-$\alpha$ and [SII] and note an excess of [SII] emission along the jet length as compared to observations. This suggests that observed beams undergo earlier processing, if they are present at all.Comment: 18 pages, 7 figures. Submitted to the Astrophysical Journa

Can we afford to live longer in better health?

This document analyses the effects of ageing populations upon public finances. More specifically, it focuses on the implications of ageing for acute health care, long-term care, and public pension expenditure. It does so for 15 EU countries. �It pays particular attention to three novel insights: (i) a large part of health care spending relates to time to death rather than to age: (ii) life expectancy may increase much faster than current demographic projections suggest, and (iii) the average health status may continue to improve in the future. It adopts a generational accounting model that incorporates health care costs during the last years of life, decomposed into an acute health care component and a long-term care component. The projections show that gains in life expectancy increase age-related expenditure; better health has the opposite effect. Combined, these trends reduce health care expenditure and increase pension expenditure. Their joint effect upon public finance is rather modest, however. Hence, the assessment of public finances in most EU15 countries does not change: even if a faster increase in life expectancy should combine with an improvement in health, current fiscal and social security institutions are unsustainable.

Rare earth elements in Andaman Island surface water : geochemical tracers for the monsoon

The Asian summer monsoon affects the lives of billions of people. With the aim of identifying geochemical tracers for the monsoon related freshwater input from the major rivers draining into the Bay of Bengal and Andaman Sea we have taken surface seawater samples from various locations up and down the Andaman Islands during 2011. Importantly, in some locations samples have been taken in March, July and November, covering most of a seasonal cycle and different monsoon phases. Samples were collected from the side of small wooden boats or while swimming and were filtered within a few hours at 0.45 or 0.22 microns using the vacuum produced by a water jet or a hand operated peristaltic pump. Filtered and unfiltered samples were acidified to < pH 2 and analysed for Y and the REEs with an automated online preconcentration ICP-MS technique [1]. The local input of REEs from streams and sediment rich areas such as mangrove environments is clearly identified by middle REE enrichments in the shale normalised patterns of some samples. These middle REE bulges accompany large increases in dissolved REE concentrations at some locations, especially for the July samples obtained during the peak monsoon season with frequent storms. Y/Ho fractionation aslo occurs during the local input of dissolved REEs with affected samples having lower Y/Ho ratios. Conversly, some samples, in particular those taken after heavy rainfall in March, show strong REE scavenging accompanied by the prefferential removal of dissolved light REEs and higher Y/Ho ratios. The time series at a location away from local input sources shows remarkably similar REE patterns and concentraions in March and July. Then in October-November, following the peak in monsoon river discharge, the dissolved REE concentration increases by almost a factor of 2. The notable exception to this seasonal pattern is the Ce anomally which is around 0.3 in March and November but 0.6 in July, implying less oxidative removal of Ce(IV) during the peak summer monsoon rains. With the exception of elevated dissolved Ce concentrations, the North Pacific Deep Water normalised REE patterns are similar to those reported for offshore samples from the Bay of Bengal and Andaman Sea [2]. These seawater normalised patterns are distinctive having a middle REE enriched arc with similar light and heavy REE values suggesting the input from large rivers in the region is traceable using seawater REE chemistry. [1] Hathorne et al. (2012), Online preconcentration ICP-MS analysis of rare earth elements in seawater, Geochem. Geophys. Geosyst., 13, Q01020, doi:10.1029/2011GC003907. [2] Amakawa et al. (2000), Geochim. Cosmochim. Acta 64, 1715-1727

Promouvoir l'agroforesterie dans les politiques publiques. Guide pour les décideurs

Les systèmes agroforestiers regroupent des techniques d'utilisation des terres à la fois traditionnelles et modernes où les arbres sont associés aux cultures et/ou aux systèmes d'élevage dans des milieux agricoles. Lorsqu'elle est conçue et mise en oeuvre correctement, l'agroforesterie allie les bonnes pratiques d'arboriculture à des systèmes agricoles, conduisant à une utilisation plus durable des terres. L'agroforesterie, pratiquée aussi bien dans les régions tropicales que tempérées, produit des aliments et des fibres qui améliorent la sécurité alimentaire et nutritionnelle. Elle soutient aussi les moyens de subsistance, réduit la pauvreté et favorise des environnements agricoles productifs et résilients. En outre, appliquée à grande échelle, elle peut renforcer les écosystèmes grâce au stockage du carbone, à la prévention de la déforestation, à la conservation de la biodiversité, à l'amélioration de la qualité de l'eau et à la lutte contre l'érosion, tout en permettant aux terres agricoles d'absorber certains effets des changements climatiques et des événements comme les inondations ou les sécheresses. Le potentiel qu'a l'agroforesterie de contribuer au développement durable a été reconnu lors de rencontres internationales sur les politiques, dont la Convention-cadre sur les changements climatiques (UNFCCC) et la Convention sur la diversité biologique des Nations Unies (CDB), justifiant ainsi l'augmentation des investissements dans son développement. Pourtant, l'agroforesterie continue à faire face à plusieurs obstacles comme des incitations politiques défavorables, une diffusion insuffisante des connaissances, des contraintes légales et une mauvaise coordination entre les multiples secteurs concernés. De plus, l'agroforesterie n'est pas suffisamment prise en compte dans la formulation des politiques nationales, dans la planification de l'utilisation des terres et dans les programmes de développement rural. De ce fait, sa contribution potentielle à l'économie et aux objectifs de développement durable n'a pas encore été pleinement reconnue ni exploitée. L'un des défis que l'agroforesterie rencontre dans de nombreux pays est la prédominance des monocultures alimentaires, des cultures industrielles et de la mécanisation (souvent subventionnées) dans les politiques agricoles, ce qui décourage l'intégration des arbres dans les exploitations. En outre, dans certains pays, les problèmes de propriété foncière et les procédures bureaucratiques nécessaires pour obtenir l'accès tant à la terre qu'aux produits des arbres créent des incertitudes à long terme qui restreignent d'autant plus les initiatives agroforestières. Les agriculteurs peuvent aussi avoir l'impression que les arbres sont incompatibles avec leurs activités agricoles, et qu'ils ne peuvent pas bénéficier des programmes offrant une formation ou un accès aux intrants liés aux arbres (matériel de reproduction, par exemple) dans la même mesure que pour d'autres types d'exploitations agricoles. La méconnaissance des avantages de l'agroforesterie conduit involontairement à la perception qu'elle est en marge de l'agriculture et qu'il s'agit d'un système faiblement productif. Le développement de l'agroforesterie est souvent entravé par des dispositions juridiques, politiques ou institutionnelles, par l'absence de rétributions pour les bénéfices environnementaux, ainsi que par le délai entre l'adoption du système et la récolte des revenus, qui décourage les investissements. Il s'avère donc nécessaire de mettre sur pied des politiques pour promouvoir les avantages de l'agroforesterie. Ce guide poursuit l'objectif général d'aider les pays à renforcer les conditions stratégiques, juridiques et institutionnelles qui facilitent l'adoption de l'agroforesterie et qui reconnaissent sa contribution au développement national. Cela inclut notamment une meilleure communication entre les secteurs et l'intégration de l'agroforesterie dans les politiques nationales. Ces lignes directrices sont le fruit d'une combinaison d'ateliers, d'interviews structurées avec des experts et d'études de cas provenant de différents pays tant développés qu'en développement

South Asian monsoon history over the past 60 kyr recorded by radiogenic isotopes and clay mineral assemblages in the Andaman Sea

The Late Quaternary variability of the South Asian (or Indian) monsoon has been linked with glacial‐interglacial and millennial scale climatic changes but past rainfall intensity in the river catchments draining into the Andaman Sea remains poorly constrained. Here we use radiogenic Sr, Nd, and Pb isotope compositions of the detrital clay‐size fraction and clay mineral assemblages obtained from sediment core NGHP Site 17 in the Andaman Sea to reconstruct the variability of the South Asian monsoon during the past 60 kyr. Over this time interval εNd values changed little, generally oscillating between −7.3 and −5.3 and the Pb isotope signatures are essentially invariable, which is in contrast to a record located further northeast in the Andaman Sea. This indicates that the source of the detrital clays did not change significantly during the last glacial and deglaciation suggesting the monsoon was spatially stable. The most likely source region is the Irrawaddy river catchment including the Indo‐Burman Ranges with a possible minor contribution from the Andaman Islands. High smectite/(illite + chlorite) ratios (up to 14), as well as low 87Sr/86Sr ratios (0.711) for the Holocene period indicate enhanced chemical weathering and a stronger South Asian monsoon compared to marine oxygen isotope stages 2 and 3. Short, smectite‐poor intervals exhibit markedly radiogenic Sr isotope compositions and document weakening of the South Asian monsoon, which may have been linked to short‐term northern Atlantic climate variability on millennial time scales

Minimal influence of recrystallization on middle Miocene benthic foraminiferal stable isotope stratigraphy in the eastern equatorial Pacific

Stable carbon and oxygen isotopes (δ13C and δ18O) of foraminiferal tests are amongst the most important tools in paleoceanography, but the extent to which recrystallization can alter the isotopic composition of the tests is not well known. Here we compare three middle Miocene (16–13 Ma) benthic foraminiferal stable isotope records from eastern equatorial Pacific sites with different diagenetic histories to investigate the effect of recrystallization. To test an extreme case, we analyzed stable isotope compositions of benthic foraminifera from Integrated Ocean Drilling Program Site U1336, for which the geochemistry of bulk carbonates and associated pore waters indicates continued diagenetic alteration in sediments > 14.7 Ma. Despite this diagenetic overprinting, the amplitudes and absolute values of the analyzed U1336 stable isotopes agree well with high-resolution records from better preserved Sites U1337 and U1338 nearby. Our results suggest that although benthic foraminiferal tests of all three sites show some degree of textural changes due to recrystallization, they have retained their original stable isotope signatures. The good agreement of the benthic foraminiferal stable isotope records demonstrates that recrystallization occurred extremely rapidly (< 100 kyr) after deposition. This is confirmed by the preservation of orbital cyclicities in U1336 stable isotope data and δ18O values being different to inorganic calcite that would precipitate from U1336 pore waters during late recrystallization. The close similarity of the benthic foraminiferal stable isotope records between the sites allows the well-resolved paleomagnetic results of Site U1336 to be transferred to Sites U1337 and U1338 improving the global geological timescale