Evaluating North American Mountain Snowpack Extent in Regional Climate Models Using MODIS Satellite Imagery

Mountain snowpack is a vital source of water for ecosystems, has a significant influence on the occurrence of wildfires, and provides water resources for billions of people globally. Despite the implications of climate change on mountain snowpack, we have few reliable ways of estimating global snowpack extent. In response to the lack of accurate methods of estimating mountain snowpack, Wrzesien et al. (2018) presented an estimate of snowpack extent for eleven North American mountain ranges using regional climate model (RCM) simulations. This research evaluates these model estimates using remote sensing imagery from the NASA Terra MODIS satellite instrument, providing further analysis of the usefulness of RCMs in estimating mountain snowpack. In comparison to MODIS, the RCM simulations generally perform well for most of the year for most ranges, though there is a trend towards spring overestimation of snow cover extent. Spatially, there is no clear trend in the performance of the RCM simulations. Further analysis using other remote sensing datasets could provide more insight into the ability of RCMs to accurately simulate mountain snowpack extent.Bachelor of Scienc

LES VARIATIONS DE L'EXTENSION DU LAC MALIQ (BASSIN DE KORÇË, ALBANIE) EN RELATION AVEC L'OCCUPATION HUMAINE ENTRE 14000 BP ET 2000 BP

International audienceDepuis le début des années 1990, les fouilles archéologiques menées dans le bassin de Korçë, notamment sur le tell de Sovjan, occupé du Néolithique ancien (7990 cal BP, soit 7060 - 6899 av. J.-C.) jusqu’à l’Âge du fer (2600 cal BP, soit 822 - 671 av. J.-C.), ont confirmé l’implantation de populations sédentaires, pratiquant l’agriculture et l’élevage depuis le Néolithique ancien (LAFE 2005 ; LERA 1990 ; LERA et al. 1996 ; TOUCHAIS et al., 2005). Il s’agit de la civilisation dite « culture de Podgorie » (KOBAS 2005 ; KORKUTI 1995 ; PRENDI 1990). La partie nord du bassin de Korçë a été occupée par le lac Maliq, jusqu’à ce qu’il soit asséché par drainage à la fin des années 1950. À cette époque, l’extension du lac variait de 40 km2 à la fin de l’été à 80 km2 (FOUACHE et al. 2001). Du Néolithique ancien à l’Âge du fer, et surtout à la période du Bronze moyen (autour de 3800 cal BP, 2310 - 2042 av. J.-C.), de nombreuses implantations humaines occupaient les rives du lac (fig. 1) comme sur le site de Maliq, le seul site « palaffitique » étudié dans le bassin (PRENDI, 1966) ou Sovjan, un site de rive (TOUCHAIS et alii, 2005).Afin de reconstituer plus précisément la densité de ces sites et d’aboutir à un modèle d’implantation humaine autour du lac Maliq, la Mission franco-albanaise a entrepris des prospections archéologiques systématiques. En préliminaire à ces prospections, des reconstitutions paléogéographiques de l’extension du lac Maliq ont été proposées pour quatre périodes clefs : autour de 14000 BP, le Mésolithique (autour de 9000 cal BP, soit 8781 - 8542 av. J.-C.), le Bronze moyen (autour de 3800 cal BP, soit 2310 - 2042 av. J.-C.) et l’Âge du fer (2600 cal BP, soit 822 - 671 av. J.-C.). Ces reconstitutions ont été réalisées à partir d’un Système d’Information Géographique (SIG) associé à un Modèle Numérique de Terrain (MNT) en trois dimension, incluant des données topographiques, géologiques, paléoenvironnementales et archéologiques.Ces reconstitutions permettent également de discuter de l’influence possible des variations climatiques holocènes sur les fluctuations du niveau du lac Maliq

Three hundred eighty thousand year long stable isotope and faunal records from the Red Sea : influence of global sea level change on hydrography

Stable isotope and faunal records from the central Red Sea show high-amplitude oscillations for the past 380,000 years. Positive δ18O anomalies indicate periods of significant salt buildup during periods of lowered sea level when water mass exchange with the Arabian Sea was reduced due to a reduced geometry of the Bab el Mandeb Strait. Salinities as high as 53‰ and 55‰ are inferred from pteropod and benthic foraminifera δ18O, respectively, for the last glacial maximum. During this period all planktonic foraminifera vanished from this part of the Red Sea. Environmental conditions improved rapidly after 13 ka as salinities decreased due to rising sea level. The foraminiferal fauna started to reappear and was fully reestablished between 9 ka and 8 ka. Spectral analysis of the planktonic δ18O record documents highest variance in the orbital eccentricity, obliquity, and precession bands, indicating a dominant influence of climatically - driven sea level change on environmental conditions in the Red Sea. Variance in the precession band is enhanced compared to the global mean marine climate record (SPECMAP), suggesting an additional influence of the Indian monsoon system on Red Sea climates

Centennial scale climate instabilities in a wet early Holocene West African monsoon

A Holocene Gulf of Guinea record of riverine runoff, based on Ba/Ca in tests of a shallow-dwelling planktic foraminifer, and sea surface temperature (SST), based on Mg/Ca, reveals centennial-scale instabilities in West African monsoon (WAM) precipitation and eastern equatorial Atlantic (EEA) thermal conditions. The long-term Holocene climate trend is characterized by a warm and wet early-mid Holocene and gradual drying and cooling during the late Holocene. Superimposed on this trend are numerous centennial scale drops in precipitation during the early-mid Holocene. The greatest declines in early Holocene monsoon precipitation were accompanied by significant SST cooling in the EEA and correlate with drops in air temperature over Greenland and fresh water outbursts into the North Atlantic (NA). This observation suggests that early Holocene climate instabilities in the NA were closely linked to changes in the WAM. The strong imprint of NA events in summer monsoon precipitation suggests that these events were not confined to winter-time. The late Holocene does not show large amplitude changes in riverine runoff at the centennial level. The relatively stable late Holocene conditions likely reflect a weakening and stabilization of the monsoon system, probably due to diminished influence of the NA region due to a reduction in ice sheet

A comparison of biomarker records of northeast African vegetation from lacustrine and marine sediments (ca. 3.40 Ma)

Author Posting. © Elsevier B.V., 2007. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Organic Geochemistry 38 (2007): 1607-1624, doi:10.1016/j.orggeochem.2007.06.008.Integrated terrestrial and marine records of northeast African vegetation are needed to provide long, high resolution records of environmental variability with established links to specific terrestrial environments. In this study, we compare records of terrestrial vegetation preserved in marine sediments in the Gulf of Aden (DSDP Site 231) and an outcrop of lacustrine sediments in the Turkana Basin, Kenya, part of the East African Rift System. We analyzed higher plant biomarkers in sediments from both deposits of known equivalent age, corresponding to a ca. 50 – 100 ka humid interval prior to the β-Tulu Bor eruption ca. 3.40 Ma, when the Lokochot Lake occupied part of the Turkana Basin. Molecular abundance distributions indicate that long chain n-alkanoic acids in marine sediments are the most reliable proxy for terrestrial vegetation (Carbon Preference Index, CPI, = 4.5), with more cautious interpretation needed for n-alkanes and lacustrine archives. Marine sediments record carbon isotopic variability in terrestrial biomarkers of 2 – 3‰, roughly equivalent to 20% variability in the C3/C4 vegetation contribution. The proportion of C4 vegetation apparently increased at times of low terrigenous dust input. Terrestrial sediments reveal much larger (2 – 10‰) shifts in n-alkanoic acid δ13C values. However, molecular abundance and isotopic composition suggest that microbial sources may also contribute fatty acids, contaminating the lacustrine sedimentary record of terrestrial vegetation.Funding was provided by the U.S. National Science Foundation HOMINID Grant 0218511

Rapport sur l'expérience exposition itinérante archéologique gallo-romaine dans l'Oise (enquête dans les écoles)

Lezine Pierre. Rapport sur l'expérience exposition itinérante archéologique gallo-romaine dans l'Oise (enquête dans les écoles). In: Revue archéologique de l'Oise, n°15, 1979. pp. 14-32

Quelques applications pratiques de l'oeuvre de Jean Piaget dans le domaine de la petite enfance

Some practical applications of Piaget work in the field of early childhood. — Report on follow up observations in Paris dary care centres, on 305 babies from 2 to 30 months of age with the double objective of studying their behaviour and contributing to a better organization of collectivities. This research study, directly inspired by Piaget surveys about the emergence of intelligence in child's mind confirms the hierarchy of sensori-motor intelligence stages ; the author having checked the trend of which, stressing the emergence of stages and of earlier behaviour observed.Relation des observations suivies dans des crèches de Paris, sur 305 bébés âgés de 2 à 30 mois, dans le double but d'étudier leur comportement et de contribuer à une meilleure organisation des collectivités. Cette recherche, directement inspirée des études de Piaget sur la naissance de l'intelligence chez l'enfant, confirme la hiérarchie des stades de l'intelligence sensori-motrice dont l'auteur a vérifié l'évolution en dégageant des stades et des conduites préalables observées.Algunas aplicaciones prácticas de la obra de Piaget en el dominio de la pequeña infancia. — Relato de observaciones llevadas en casas-cunas de Paris sobre 305 niñas de edad de 2 a 30 meses, con la doble finalidad de estudiar su comportamiento y de contribuir a una mejor organización de las colectividades. Esta investigación, directamente inspirada por los estudios de Piaget sobre el nacimiento de la inteligencia en el niño, confirma la jerarquia de los estadios de la inteligencia sensorio-motórica de la que el autor ha verificado la evolución despejando la apariciôn de los estadios y de las conductas previas observadas.Lezine Irène. Quelques applications pratiques de l'oeuvre de Jean Piaget dans le domaine de la petite enfance. In: Revue française de pédagogie, volume 57, 1981. pp. 22-29

Paleoenvironnements vegetaux d'Afrique nord-tropicale depuis 12000 B.P. : analyse pollinique de series sedimentaires continentales (Senegal-Mauritanie)

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Data for: The Senegal River during the last millennium

Pollen raw counts for SL 14-0