Glacier recession and human vulnerability in the Yanamarey watershed of the Cordillera Blanca, Peru

Glaciers in the Cordillera Blanca, Peru, are undergoing rapid retreat, in large part due to climate change. These changes are significantly altering water availability in the region and pose critical risks to local populations that are highly dependent on these resources for livelihoods. We examine these issues through an interdisciplinary and linked evaluation of hydrological change and livelihood vulnerability in the Yanamarey watershed. Physical observations of the Yanamarey glacier show acceleration in frontal retreat at a rate of 8 m decade^???1 since 1970, accompanied by total volume loss on the order of 0.022 km³. Hydrological and hydrochemical analyses document a possible transformation of stream flow over the past decade as the seasonal storage capacity of the glacier has degraded. Recent stream discharge measurements from the proglacial lake below the glacier are more coincident with the highly variable seasonal precipitation than they were during the 1998?C1999 hydrological year. Local household perceptions of glacier recession and seasonal hydrological variability agree with this trend, which is increasing human vulnerability in the watershed. Household case-study survey results demonstrate that shifting water resources, increasing weather extremes and climate-related threats to tourism are all new vectors of vulnerability for household livelihoods.     

Instability in spatial error models: an application to the hypothesis of convergence in the European case

This paper focuses on the hypothesis of stability in the mechanisms of spatial dependence that are usually employed in spatial econometric models. We propose a specification strategy for which the first step is to solve a local estimation algorithm, called the Zoom estimation. The aim of this stage is to detect problems of heterogeneity in the parameters and to identify the regimes. Then we resort to a battery of formal Lagrange Multipliers to test the assumption of stability in the processes of spatial dependence. The alternative hypothesis consists of the existence of several regimes in these parameters. A small Monte Carlo serves to confirm the behaviour of this strategy in a context of finite size samples. As an illustration, we solve an application to the case of the hypothesis of convergence for the per capita income in the European regions. Our results reveal the existence of a strong Centre-Periphery dichotomy in which instability extends to all the elements (coefficients of regression as well as parameters of spatial dependence) that intervene in a classical conditional β-convergence model.     

Origin of peraluminous granites and granodiorites, Iberian massif, Spain: an experimental test of granite petrogenesis

The discrimination between potential source materials involved in the genesis of Iberian granites and granodiorites, as well as the role of mantle-crust interactions, are examined using constraints imposed by melting experiments, melting-assimilation experiments and Sr-Nd isotope systematics. The Sr-Nd isotope relationships indicate the existence of different genetic trends in which juvenile mantle materials are involved by different mechanisms: (1) a source trend, traced by a particular evolution of the pre-Hercynian basement and indicating mantle participation at the time of sedimentation; (2) a set of magmatic trends traced by gabbro-tonalite-enclave-granodiorite associations, implying the incorporation of new mantle material at the time of granite generation. These relationships strongly support a pure crustal origin for the peraluminous leucogranites, derived from partial melting of crustal protoliths, and a hybrid origin for the peraluminous granodiorites. These granodiorites are the most abundant granitic rocks of the Central Iberian zone (CIZ) of the Iberian massif, implying that processes of hybridisation by assimilation and/or magma mixing played an important role in granitoid production during the Hercynian orogeny. These hypotheses have been tested by means of melting and assimilation experiments. Melting experiments in the range 800–900 °C and at pressures of 3, 6, 10 and 15 kbar indicate that: (1) several potential source materials such as Bt-Ms gneisses and metagreywackes are suitable for the production of peraluminous leucogranite melts; (2) the melt compositions are always leucogranitic, regardless of pressure; (3) pressure exerts a strong influence on the fertility of the source: experiments at 3 kbar produce more than 20 vol% of melt, compared with less than 5 vol% of melt produced at 10 and 15 kbar and at the same temperature. The melting-assimilation experiments carried out at 1000 °C and 4, 7 and 10 kbar and using a proportion of 50% gabbro and 50% gneiss give high melt proportions (more than 50 vol.%) and noritic residues. These melts have the composition of leucogranodiorites, and overlap with part of the compositional range of peraluminous granodiorites of the Iberian massif. The generation of more mafic granodiorites may be explained by the incorporation of some residual orthopyroxene to the granodiorite magmas. The low solubility of Fe + Mg prevents the generation of granodiorite melts with more than 3 wt% of MgO + FeO at all crustal pressures. The large volumes of peraluminous, hybrid granodiorites, produced by assimilation of crustal rocks by mantle magmas, imply that an important episode of crustal growth took place during the Late-Palaeozoic Hercynian orogeny in the Iberian massif. Received: 30 June 1998 / Accepted: 27 November 1998     

HIDDRA: a highly independent data distribution and retrieval architecture for space observation missions

Institutions such as NASA, ESA or JAXA find solutions to distribute data from their missions to the scientific community, and their long term archives. This is a complex problem, as it includes a vast amount of data, several geographically distributed archives, heterogeneous architectures with heterogeneous networks, and users spread around the world. We propose a novel architecture that solves this problem aiming to fulfill the requirements of the final user. Our architecture is a modular system that provides a highly efficient parallel multiprotocol download engine, using a publisher/subscriber policy which helps the final user to obtain data of interest transparently. We have evaluated a first prototype, in collaboration with the ESAC centre in Villafranca del Castillo (Spain) that shows a high scalability and performance, opening a wide spectrum of opportunities.