Glaciers and Global Warming

Ice core and mass balance studies from glaciers, ice caps and ice sheets constitute an ideal medium for monitoring and studying present and past environmental change and, as such, make a valuable contribution to the present debate over anthropogenic forcing of climate. Data derived from 32 years of measurements in the Canadian Arctic show no significant trends in glacier mass balance, ice melt, or snow accumulation, although the mass balance continues to be slightly negative. Models suggest that industrial aerosol loading of the atmosphere should add to the warming effect of greenhouse gases. However, we have found a sharp increase in the concentration of industrial pollutants in snow deposited since the early 1950's which makes the trendless nature of our various time series surprising. Spatial differences in the nature of climatic change may account for the lack of trend in the Queen Elizabeth Islands but encourages similar investigations to this study elsewhere in the circumpolar region. A global warming trend over the past 150 years has been demonstrated from instrumental data and is evident in our ice cores. However, the ice core data and glacier geometry changes in the Canadian Arctic suggest the Arctic warming is more pronounced in summer than winter. The same warming trend is not unique when viewed in the context of changes over the past 10,000 or 100,000 years. This suggests the 150-year trend is part of the natural climate variability.L'analyse des carottes de glace et les mesures du bilan de masse des glaciers, des calottes glaciaires et des indlandsis permettent de déceler des changements environnementaux survenus dans le passé tout en permettant de surveiller les changements actuels. Ces études peuvent contribuer au débat portant sur les conséquences physiques de l'activité humaine sur le climat. Trente-deux ans de données accumulées sur les bilans de masse, la fonte et l'accumulation de neige sur les glaciers de l'Arctique canadien ne montrent aucune tendance significative, bien que les bilans de masse soient quelque peu négatifs. Les modèles prévoient pourtant un réchauffement provoqué par l'apport accru d'aérosols d'origine industrielle. Nous observons une forte augmentation des concentrations de polluants industriels dans la neige déposée depuis les années cinquante, ce qui rend l'absence d'une tendance dans nos observations encore plus surprenante. L'absence d'indices sur un réchauffement dans l'archipel de la Reine-Élisabeth est peut-être simplement attribuable aux variations régionales du changement climatique, un phénomène qui devrait être étudié dans d'autres régions circumpolaires. Depuis 150 ans, une tendance vers un réchauffement à l'échelle planétaire a été observée à partir des données recueillies par les instruments ainsi que dans les carottes de glace. Les données obtenues à partir des carottes de glace et de la géométrie des glaciers semblent indiquer que ce réchauffement est plus marqué l'été que l'hiver. La tendance au réchauffement n'est cependant pas exceptionnelle dans le contexte des 10 000 ou 100 000 dernières années; elle pourrait rendre compte de la variabilité naturelle du climat.Die Analyse von Eisbohrkernen und das Studium der Bilanz der Masse von Gletschem, Eiskappen und Eisdecken sind ein ausgezeichnetes Mittel, um gegenwàrtige und vergangene Umweltverânderungen zu kontrollieren und zu studieren. So kann ein wertvoller Beitrag zur gegenwàrtigen Débatte ùber den Einfluft der menschlichen Aktivitàt auf das Klima geleistet werden. Die Daten, die man durch Messungen ùber 32 Jahre in der kanadischen Arktis gewann, zeigen keine erhebliche Tendenz in der Bilanz der Gletschermasse, Eisschmelze oder Schneeakkumulation, auch wenn die Bilanz der Masse weiter leicht negativ ist. Die Modelle lassen vermuten, da8 die Ladung der Atmosphère mit Industrieaerosolen zum Treibhauseffekt beitrâgt. Jedoch haben wir einen starken Anstieg in der Konzentration industrieller Schadstoffe in dem seit den frùhen fùnfziger Jahren angesammelten Schnee, was das Fehlen einer Tendenz in unseren verschiedenen Zeitabschnitten ùberraschend macht. Ôrtliche Unterschiede in der Natur der Klimawechsel mogen fur das Fehlen einer Tendenz auf den Queen Elizabeth lnseln verantwortlich sein, doch dieser Untersuchung vergleichbare Studien sollten andernorts in der Region um den PoI durchgefùhrt werden. Eine globale Erwàrmungstendenz ùber die vergangenen 150 Jahre konnte mittels instrumenteller Messungen festgestellt werden und ist in unseren Eisbohrkernen sichtbar. Indessen lassen die Eisbohrkerndaten und Verànderungen in der Géométrie der Gletscher in der kanadischen Arktis annehmen, daft die Erwàrmung der Arktis im Sommer deutlicher ist als im Winter. Dièse Erwàrmungstendenz ist nicht auftergewôhnlich, wenn man sie im Kontext der Verânderungen in den letzten 10,000 oder 100,000 Jahren sieht. Die 150 Jahre-Tendenz ist wohl Teil der natùrlichen Klimavariabilitàt

Preservation of glaciochemical time-series in snow and ice from the Penny Ice Cap, Baffin Island

A detailed investigation of major ion concentrations of snow and ice in the summit region of Penny Ice Cap (PIC) was performed to determine the effects of summer melt on the glaciochemical time-series. While ion migration due to meltwater percolation makes it difficult to confidently count annual layers in the glaciochemical profiles, time-series of these parameters do show good structure and a strong one year spectral component, suggesting that annual to biannual signals are preserved in PIC glaciochemical records

Forty-seven Years of Research on the Devon Island Ice Cap, Arctic Canada

The Devon Island ice cap has been the subject of scientific study for almost half a century, beginning with the first mass balance measurements in 1961. Research on the ice cap was the first to investigate (1) the role of meltwater in seasonal ice-velocity variations on a polythermal Arctic ice cap, (2) the use of air temperature rather than net radiation as a proxy for the energy driving surface melt, and (3) the influence of the changing frequency of specific synoptic weather configurations on glacier melt and mass balance. Other research has included investigations of ice cap geometry, flow dynamics, and mass balance; ice core analyses for records of past climate and contaminant deposition; and studies of changes in ice cap area and volume and their relationship to surface mass balance and ice dynamics. Current research includes ground studies connected to efforts to calibrate and validate the radar altimeter that will be carried by the European Space Agency’s (ESA) CryoSat2 satellite, and a major collaborative Canadian International Polar Year (IPY) project focused on the Belcher Glacier, on the northeast side of the ice cap, that examines hydrodynamics of large tidewater glaciers. This paper summarizes our current knowledge of the Devon Island ice cap and identifies some of the outstanding questions that continue to limit our understanding of climate-ice cap interactions in Arctic regions.La calotte glaciaire de l’île Devon fait l’objet d’une étude scientifique depuis près d’un demi-siècle, les premières mesures du bilan massique remontant à 1961. C’est la première fois que des travaux de recherche sur la calotte glaciaire permettent de faire enquête sur 1) le rôle de l’eau de fonte dans les variations caractérisant la vélocité de la glace d’une calotte glaciaire polytherme de l’Arctique; 2) l’utilisation de la température de l’air au lieu du bilan radiatif en surface en guise d’approximation pour la fonte superficielle conductrice d’énergie, et 3) l’influence exercée par la fréquence changeante de configurations climatiques synoptiques spécifiques sur la fonte du glacier et le bilan massique. Parmi les autres travaux de recherche, notons des enquêtes sur la géométrie de la calotte glaciaire, la dynamique des débits d’écoulement et le bilan massique; l’analyse des enregistrements relatifs aux carottes glaciaires en ce qui a trait à d’anciens dépôts climatiques et dépôts de contaminants; et l’étude des changements caractérisant l’aire et le volume de la calotte glaciaire de même que leur relation par rapport au bilan massique en surface et à la dynamique des glaces. Par ailleurs, les travaux de recherche actuels prennent la forme d’études sur le terrain se rapportant aux efforts visant à calibrer et à valider l’altimètre radar, études qui seront effectuées par le satellite CryoSat2 de l’Agence spatiale européenne (ASE), et un projet d’envergure en collaboration avec l’Année polaire internationale (API) au Canada portant sur le glacier Belcher, du côté nord-est de la carotte glaciaire, projet qui examine l’hydrodynamique des gros glaciers de marée. La présente communication résume nos connaissances actuelles de la calotte glaciaire de l’île Devon de même que certaines des questions en suspens qui continuent de restreindre la façon dont nous comprenons les interactions entre le climat et la calotte glaciaire dans les régions arctiques

The Effects of Flowline Length Evolution on Chemistry-Delta O-18 Profiles from Penny Ice Cap, Baffin Island, Canada

The isotopic and chemical signatures for ice-age and Holocene ice from Summit, Greenland and Penny Ice Cap, Baffin Island, Canada, arc compared. The usual pattern of low delta(18)O, high Ca2+ and high Cl- is presented in the Summit records, but Penny Ice Cap has lower than present Cl- in its ice-age ice. A simple extension of the Hansson model (Hansson, 1994) is developed and used to simulate these signatures. The low ice-age Cl- from Penny Ice Cap is explained by having the ice-age ice originating many thousands of km inland near the centre of the Laurentide ice sheet and much further from the marine sources. Summit\u27s flowlines all start close to the present site. The Penny Ice Cap early-Holocene delta(18)O\u27s had to be corrected to offset the Laurentide meltwater distortion. The analysis suggests that presently the Summit and Penny Ice Cap marine impurity originates about,500 km away, and that presently Penny Ice Cap receives a significant amount of local continental impurity

Increasing Waterflood Reserves in the Wilmington Oil Field Through Improved Reservoir Characterization and Reservoir Management.

The objectives of this quarterly report are to summarize the work conducted under each task during the reporting period April - June 1997 and to report all technical data and findings as specified in the `Federal Assistance Reporting Checklist`. The main objective of this project is the transfer of technologies, methodologies, and findings developed and applied in this project to other operators of Slope and Basin Clastic Reservoirs. This project will study methods to identify sands with high remaining oil saturation and to recomplete existing wells using advanced completion technology. The identification of the sands with high remaining oil saturation will be accomplished by developing a deterministic three dimensional (3-D) geologic model and by using a state of the art reservoir management computer software. The wells identified by the geologic and reservoir engineering work as having the best potential will be logged with a pulsed acoustic cased-hole logging tool. The application of the logging tools will be optimized in the lab by developing a rock-log model. This rock-log model will allow us to convert shear wave velocity measured through casing into effective porosity and hydrocarbon saturation. The wells that are shown to have the best oil production potential will be recompleted. The recompletions will be optimized by evaluating short radius and ultra-short radius lateral recompletions as well as other techniques

Global change effects on plant communities are magnified by time and the number of global change factors imposed

Global change drivers (GCDs) are expected to alter community structure and consequently, the services that ecosystems provide. Yet, few experimental investigations have examined effects of GCDs on plant community structure across multiple ecosystem types, and those that do exist present conflicting patterns. In an unprecedented global synthesis of over 100 experiments that manipulated factors linked to GCDs, we show that herbaceous plant community responses depend on experimental manipulation length and number of factors manipulated. We found that plant communities are fairly resistant to experimentally manipulated GCDs in the short term (<10 y). In contrast, long-term (≥10 y) experiments show increasing community divergence of treatments from control conditions. Surprisingly, these community responses occurred with similar frequency across the GCD types manipulated in our database. However, community responses were more common when 3 or more GCDs were simultaneously manipulated, suggesting the emergence of additive or synergistic effects of multiple drivers, particularly over long time periods. In half of the cases, GCD manipulations caused a difference in community composition without a corresponding species richness difference, indicating that species reordering or replacement is an important mechanism of community responses to GCDs and should be given greater consideration when examining consequences of GCDs for the biodiversity–ecosystem function relationship. Human activities are currently driving unparalleled global changes worldwide. Our analyses provide the most comprehensive evidence to date that these human activities may have widespread impacts on plant community composition globally, which will increase in frequency over time and be greater in areas where communities face multiple GCDs simultaneously

Measurement of the νe−\nu_e-Nucleus Charged-Current Double-Differential Cross Section at <Eν>=\left< E_{\nu} \right> = 2.4 GeV using NOvA

The inclusive electron neutrino charged-current cross section is measured in the NOvA near detector using $8.02\times10^{20}$ protons-on-target (POT) in the NuMI beam. The sample of GeV electron neutrino interactions is the largest analyzed to date and is limited by $\simeq$ 17\% systematic rather than the $\simeq$ 7.4\% statistical uncertainties. The double-differential cross section in final-state electron energy and angle is presented for the first time, together with the single-differential dependence on $Q^{2}$ (squared four-momentum transfer) and energy, in the range 1 GeV $\leq E_{\nu} <$6 GeV. Detailed comparisons are made to the predictions of the GENIE, GiBUU, NEUT, and NuWro neutrino event generators. The data do not strongly favor a model over the others consistently across all three cross sections measured, though some models have especially good or poor agreement in the single differential cross section vs. $Q^{2}$

Search for CP-violating Neutrino Non-Standard Interactions with the NOvA Experiment

This Letter reports a search for charge-parity (CP) symmetry violating non-standard interactions (NSI) of neutrinos with matter using the NOvA Experiment, and examines their effects on the determination of the standard oscillation parameters. Data from $\nu_{\mu}(\bar{\nu}_{\mu})\rightarrow\nu_{\mu}(\bar{\nu}_{\mu})$ and $\nu_{\mu}(\bar{\nu}_{\mu})\rightarrow\nu_{e}(\bar{\nu}_{e})$ oscillation channels are used to measure the effect of the NSI parameters $\varepsilon_{e\mu}$ and $\varepsilon_{e\tau}$. With 90% C.L. the magnitudes of the NSI couplings are constrained to be $|\varepsilon_{e\mu}| \, \lesssim 0.3$ and $|\varepsilon_{e\tau}| \, \lesssim 0.4$. A degeneracy at $|\varepsilon_{e\tau}| \, \approx 1.8$ is reported, and we observe that the presence of NSI limits sensitivity to the standard CP phase $\delta_{\tiny\text{CP}}$