Applied Filters
- Geosciences
Journal Title
Topics
- Earth and Environmental Sciences27
- Integrative Sciences7
- Biological and Life Sciences6
- Marine and Aquatic Sciences6
- Conservation and Sustainability5
- Ecology and Evolution5
- Atmospheric and Climate Sciences3
- Engineering, Technology, and Mathematics2
- Mathematics and Statistics1
- Microbiology1
- Physical Sciences1
- Physics1
- Science and Policy1
- Science and Society1
- Technology1
Publication Date
Author
- Dunnington, Dewey W2
- Spooner, Ian S2
- Akeju, Tolutope1
- Arnold, Lauren1
- Atkinson, Gail M1
- Bates, Lara M1
- Battigelli, Jeffrey1
- Boczulak, Stacy A1
- Bonannella, Carmelo1
- Bone, Christopher1
- Brault, M -O1
- Brown, Melisa1
- Brown, Vernon1
- Bundala, Mariam1
- Campbell, Linda M1
- Cannon, Sara1
- Cardini, Adriana M1
- Casson, N J1
- Caño, Dioniz1
- Chaudhuri, Chiranjib1
- Chmura, Gail L1
- Collins, Matthew J1
- Cook, Alison1
- Copeland, Les1
- Copland, Luke1
Access Type
21 - 27of27
Save this search
Please login to be able to save your searches and receive alerts for new content matching your search criteria.
Filters
Search Name | Searched On |
---|---|
Subject Areas: Geosciences (27) | 18 May 2024 |
You do not have any saved searches
- OPEN ACCESSWe examine the importance of the rock weathering feedback mechanism during the last deglacial period (∼16 000–4000 BCE) using an Earth system model of intermediate complexity (the University of Victoria Earth System Climate Model (UVic ESCM)) with four box-model parameterizations of terrestrial weathering. The deglacial climate change is driven by changes in orbital parameters, ice core reconstructions of atmospheric CO2 variability, and prescribed removal of continental ice sheets. Over the course of the 12 000 year simulation period, increases in weathering provide a mechanism that slowly removes CO2 from the atmosphere, in opposition to the observed atmospheric CO2 increase during this period. These processes transfer both carbon and alkalinity to the ocean, the combination of which results in as much as a 1000 Pg C increase in total ocean carbon, relative to a control simulation with constant weathering. However, the rapid expansion of northern hemisphere vegetation introduces a significant uncertainty among the weathering parameterizations. Further experiments to test the individual impacts of weathering dissolved inorganic carbon and alkalinity fluxes on ocean biogeochemistry suggest that the worldwide distribution of rock types and the ratio of carbonate to silicate weathering may be crucially important in obtaining an accurate estimate of changes in global weathering rates.
- OPEN ACCESSAn ordinary differential equation describing the transverse profiles of U-shaped glacial valleys has two formal analogies, which we explore in detail, bridging these different areas of research. First, an analogy with point particle mechanics completes the description of the solutions. Second, an analogy with the Friedmann equation of relativistic cosmology shows that the analogue of a glacial valley profile is a universe with a future singularity of interest in theoretical models of cosmology. A Big Freeze singularity, which was not previously observed for positive curvature index, is also contained in the dynamics.
- OPEN ACCESSAmmonium deposition at the International Institute for Sustainable Development Experimental Lakes Area (IISD–ELA), in northwestern Ontario, Canada, has doubled in the last 45 years and thus is no longer among the low nitrogen (N) deposition sites in North America. This may be related to the concurrent intensification of Manitoba agriculture to the west and upwind of the ELA. Large increases in ammonium deposition at the ELA were important in driving the observed trend and increased the NH4 + to NO3 − ratio of input to aquatic and terrestrial systems. Stable isotope analyses of two years of bulk (wet and dry) atmospheric deposition revealed very large ranges in δ15N−NH4 + (22‰ range), δ15N−NO3 − (18‰), and δ18O–NO3 − (19‰). Few other δ15N−NH4 +, δ15N−NO3 −, and δ18O–NO3 − values have been published for Canadian precipitation. Increases in δ15N of NH4 + and NO3 − in July occurred with increases in total N deposition. The wide range and seasonal trends of δ15N and δ18O values in ELA precipitation mean that studies characterizing N inputs to watersheds and lakes require an ongoing and comprehensive annual sampling regime. Global trends of declining δ15N of N deposition evident in lake sediment records may be a result of increases in NH4 + deposition with lower δ15N−NH4 + values. Similarly, the relationship in Lake Superior between increasing NO3 − and lower δ15N−NO3 − values may be explained by increased atmospheric deposition of N with low δ15N values.
- OPEN ACCESSOrnithomimid material from the Belly River Group (Campanian) of Alberta, Canada is described as sharing characters with Qiupalong henanensis from the Qiupa Formation of Henan Province, China. Derived characters and character combinations of the pubis and astragalocalcaneum were previously used to diagnose Q. henanensis and support the referral of this material to Qiupalong sp., representing the first known occurrences of Qiupalong outside of China. Qiupalong is the sixth ornithomimid taxon to be reported from the Dinosaur Park Formation and the first ornithomimid genus with a transcontinental distribution. The Alberta material represents the oldest known occurrences of Qiupalong, and a reconsideration of character evidence suggests that this genus is phylogenetically nested within other North American ornithomimids. A North American origin for Qiupalong and subsequent dispersal to Asia is proposed.
- OPEN ACCESS
- Dewey W. Dunnington,
- Hilary White,
- Ian S. Spooner,
- Mark L. Mallory,
- Chris White,
- Nelson J. O’Driscoll, and
- Nic R. McLellan
We used a paleolimnological approach at Long Lake, Nova Scotia, to construct a 10 500-year record of metal deposition in lakebed sediments and elucidate the influence of both natural and anthropogenic environmental changes. Aquatic sediment concentrations of mercury (Hg), arsenic (As), and chromium (Cr) in Long Lake fluctuated substantially and, during some periods, exceeded guidelines for the protection of aquatic life. Increases in lead (Pb), Hg, Cr, trace metals, and nitrogen stable isotopes (δ15N) were broadly coincident with a period of widespread drying from ca. 8000 to 4000 cal BP and were likely a consequence of regional fires. From ca. 4000 cal BP until 1700 AD, metal levels in general were low due to decreased erosion, increased precipitation, and reduced fire activity. Water level lowering and forced sediment aggradation (tiding) in the 1800s led to increases in minerogenic Pb and Cr, though fossil fuel combustion also likely contributed to total Pb concentrations. Stratigraphic proxies indicated increased inorganic sedimentation rates, and reduced autochthonous productivity were coincident with lower Hg and As concentrations in the Long Lake sediment. Our data indicate that natural phenomena (fire) can result in sediment contaminant exceedances, that most metals have multiple sources, and that both human-induced disturbance and emissions have contributed to Pb contamination in the last 200 years. In addition, wetter and generally cooler climate appeared to favour lower concentrations of contaminants in lake sediments. Although wetland sediments in the Cumberland Basin Marshes are not heavily polluted with metals, the development of constructed wetlands and the disruption of aquatic sediments have the potential to concentrate, mobilize, and increase the bioavailability of metals. - OPEN ACCESSThere has been a significant increase in the rate of felt earthquakes in western Alberta and eastern British Columbia, which has been associated with hydraulic fracturing and wastewater disposal. The increased rate of seismicity and the potential for localized strong ground motions from very shallow events poses an increased hazard to critical infrastructure such as major dams—particularly for older high-consequence structures. This paper overviews the factors that affect the likelihood of damaging ground motions and examines their implications for hazard assessment and mitigation. A strategy aimed at reducing the likelihood of potentially damaging ground motions to achieve probabilistic targets for critical facilities is developed, comprising elements of both mitigation and avoidance. For critical facilities, an effective strategy includes (i) an exclusion zone having a radius of ∼5 km; and (ii) a monitoring-and-response protocol to track the rate of events at the M > 2 level within 25 km, with adjustment of operational practices if required. An exclusion zone provides a deterministic safety margin to ensure the integrity of those few facilities for which failure consequences are unacceptable. Real-time monitoring tied to a response protocol can be used to control the rate of significant events and thereby limit the hazard more broadly.
- OPEN ACCESSWe describe the underwater light field of the Strait of Georgia in spring and summer, using apparent optical properties (reflectance, attenuation coefficient of downwelling irradiance, the average cosine of downwelling irradiance, and the attenuation of scalar irradiance). Both the attenuation and reflectance of photosynthetically available radiation (PAR; 400–700 nm) are highest in the turbid waters of the Fraser River plume, due to scattering by mainly inorganic particles and absorption by coloured dissolved organic matter, phytoplankton, and other organic particles. Light is most diffuse in the surface waters of the plume and least diffuse at depth and away from the plume. Throughout the Strait, blue and red wavelengths are attenuated most rapidly resulting in a green peak of reflectance, the portion of the electromagnetic spectrum that penetrates the most deeply. PAR is attenuated to 1% of its surface intensity within 6–22 m in the spring and 4–23 m in the summer. For red and blue light, the depth of 1% penetration is never deeper than 9 m. All of the visible radiation, with the exception of some green light, is absorbed within the outflowing layer (15–30 m) that is exported from the Strait with the estuarine circulation. The rapid extinction of light helps to explain the very shallow distribution of phytoplankton.