Impact of climate change on the hydrogeology of two basins in northern France

This study presents an analysis of climate-change impacts on the water resources of two basins located in northern France, by integrating four sources of uncertainty: climate modelling, hydrological modelling, downscaling methods, and emission scenarios. The analysis focused on the evolution of the water budget, the river discharges and piezometric heads. Seven hydrological models were used, from lumped rainfall-discharge to distributed hydrogeological models, and led to quite different estimates of the water-balance components. One of the hydrological models, CLSM, was found to be unable to simulate the increased water stress and was, thus, considered as an outlier even though it gave fair results for the present day compared to observations. Although there were large differences in the results between the models, there was a marked tendency towards a decrease of the water resource in the rivers and aquifers (on average in 2050 about ?14 % and ?2.5 m, respectively), associated with global warming and a reduction in annual precipitation (on average in 2050 +2.1 K and ?3 %, respectively). The uncertainty associated to climate models was shown to clearly dominate, while the three others were about the same order of magnitude and 3–4 times lower. In terms of impact, the results found in this work are rather different from those obtained in a previous study, even though two of the hydrological models and one of the climate models were used in both studies. This emphasizes the need for a survey of the climatic-change impact on the water resource.     

Infrared imaging spectroscopy with micron resolution of Sutter's Mill meteorite grains

Synchrotron‐based Fourier transform infrared spectroscopy and Raman spectroscopy are applied with submicrometer spatial resolution to multiple grains of Sutter's Mill meteorite, a regolith breccia with CM1 and CM2 lithologies. The Raman and infrared active functional groups reveal the nature and distribution of organic and mineral components and confirm that SM12 reached higher metamorphism temperatures than SM2. The spatial distributions of carbonates and organic matter are negatively correlated. The spatial distributions of aliphatic organic matter and OH relative to the distributions of silicates in SM2 differ from those in SM12, supporting a hypothesis that the parent body of Sutter's Mill is a combination of multiple bodies with different origins. The high aliphatic CH₂/CH₃ ratios determined from band intensities for SM2 and SM12 grains are similar to those of IDPs and less altered carbonaceous chondrites, and they are significantly higher than those in other CM chondrites and diffuse ISM objects.     

Oxygen isotope and chemical compositions of magnetite and olivine in the anomalous CK3 Watson 002 and ungrouped Asuka‐881595 carbonaceous chondrites: Effects of parent body metamorphism

We report in situ O isotope and chemical compositions of magnetite and olivine in chondrules of the carbonaceous chondrites Watson‐002 (anomalous CK3) and Asuka (A)‐881595 (ungrouped C3). Magnetite in Watson‐002 occurs as inclusion‐free subhedral grains and rounded inclusion‐bearing porous grains replacing Fe,Ni‐metal. In A‐881595, magnetite is almost entirely inclusion‐free and coexists with Ni‐rich sulfide and less abundant Ni‐poor metal. Oxygen isotope compositions of chondrule olivine in both meteorites plot along carbonaceous chondrite anhydrous mineral (CCAM) line with a slope of approximately 1 and show a range of Δ¹⁷O values (from approximately ?3 to ?6‰). One chondrule from each sample was found to contain O isotopically heterogeneous olivine, probably relict grains. Oxygen isotope compositions of magnetite in A‐881595 plot along a mass‐dependent fractionation line with a slope of 0.5 and show a range of Δ¹⁷O values from ?2.4‰ to ?1.1‰. Oxygen isotope compositions of magnetite in Watson‐002 cluster near the CCAM line and a Δ¹⁷O value of ?4.0‰ to ?2.9‰. These observations indicate that magnetite and chondrule olivine are in O isotope disequilibrium, and, therefore, not cogenetic. We infer that magnetite in CK chondrites formed by the oxidation of pre‐existing metal grains by an aqueous fluid during parent body alteration, in agreement with previous studies. The differences in Δ¹⁷O values of magnetite between Watson‐002 and A‐881595 can be attributed to their different thermal histories: the former experienced a higher degree of thermal metamorphism that led to the O isotope exchange between magnetite and adjacent silicates.     

NIGHTGLOW: an instrument to measure the Earth’s nighttime ultraviolet glow—results from the first engineering flight

We have designed and built an instrument to measure and monitor the “nightglow” of the Earth’s atmosphere in the near ultraviolet (NUV). In this paper we describe the design of this instrument, called NIGHTGLOW. NIGHTGLOW is designed to be flown from a high altitude research balloon, and circumnavigate the globe. NIGHTGLOW is a NASA, University of Utah, and New Mexico State University project. A test flight took place from Palestine, Texas on July 5, 2000, lasting about 8 h. The instrument performed well and landed safely in Stiles, Texas with little damage. The resulting measurements of the NUV nightglow are compared with previous measurements from sounding rockets and balloons.     

Radiating dike swarms on Venus: evidence for emplacement at zones of neutral buoyancy

Theoretical calculations of extrusive volcanic degassing on Venus yield atmospheric pressure-related rock density profiles consistent with the formation of magma neutral buoyancy zones and magma reservoirs at different depths as a function of altitude (Head and Wilson, J. geophys. Res. 97, 3877, 1992). Global analysis of radiating dike swarms interpreted to originate at magma reservoirs show that their distribution matches these predictions across approximately 90% of the planet's surface; only those highland regions whose elevations exceed 6053 km appear anomalous. The distribution of the large volcano population (extrusive reservoir products) (Keddie and Head, Planet. Space Sci. 42, 455, 1994) has yielded similar results. Comparison between the dike swarm (intrusive) and large volcano (extrusive) populations suggests that neutral buoyancy plays an important role in governing volcanic processes near the venusian surface and that the depth to the level of neutral buoyancy increases systematically at altitudes above 6051 km.     

40Ar‐39Ar studies of whole rock nakhlites: Evidence for the timing of formation and aqueous alteration on Mars

Abstract— 20–25 mg whole rock samples of the nakhlites Lafayette and Nakhla have been analyzed via the ⁴⁰Ar‐³⁹Ar technique, in part to verify their formation ages, but primarily, in an attempt to determine the timing of aqueous alteration in these martian meteorites. As in previous studies, plateaus in apparent age are observed at about 1300 Ma (1322 ± 10 for Lafayette, 1332 ± 10 and 1323 ± 11 for Nakhla), presumably corresponding to crystallization ages. The plateaus are not entirely flat, perhaps reflecting the effects of recoil during creation of ³⁹Ar in the nuclear irradiation. The first 5–20% of the K‐derived Ar released from all three samples give apparent ages <1300 Ma. Coupled with the fact that chronometric isotopic studies of nakhlites typically show some disturbance, we believe the low temperature pattern represents more recent (than 1300 Ma) formation of martian aqueous alteration products such as iddingsite. No low temperature plateaus are observed. This is consistent with petrographic evidence for multiple formation events, although the lack of low temperature plateaus is far from conclusive. On the other hand, if there was a single time of alteration, we believe that it will be difficult, if not impossible, to determine it using the K‐Ar system.     

The profile and polarization of the coronal Lα line

We calculate the profile and polarization of the Lα line in the solar corona. Coronal temperature variation, solar wind and other non-thermal motions have been taken into account. Because of the relatively low atomic weight of hydrogen the profile of the Lα line is a sensitive indicator of the coronal temperature. The line polarization contains relatively little information except for strong magnetic fields (> 70 G).