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Northern Canada (northern + canada)

Distribution by Scientific Domains
Life Sciences35%
Earth and Environmental Science28%

Selected Abstracts

Environment, race and nation reconsidered: reflections on Aboriginal land claims in Canada

THE CANADIAN GEOGRAPHER/LE GEOGRAPHE CANADIEN, Issue 4 2003
Peter J. Usher
The course of development in Northern Canada has been transformed in the last 30 years by the comprehensive land claims process. For much of the twentieth century, the settlement and development of northern Canada was experienced by Aboriginal people as a continuing process of encroachment on (and sometimes transformation of) their traditional territories, and of restriction of their customary livelihood. Examples of this process included the alteration of river systems by impoundment and diversion, the pollution and contamination of river systems, government restrictions on hunting and fishing and population relocation and sedentarization. Aboriginal political and legal action led, in the 1970s, to the establishment of a formal process for resolving Aboriginal land claims, and to revised judicial interpretation of Aboriginal and treaty rights. The paper describes how geographers have contributed to documenting those claims, and how land claims settlements have altered the land and resource regimes in northern Canada, and concludes with some observations on the effectiveness of those remedies, and on the changes in Canadian perspectives on Aboriginal northerners, the northern environment and northern development. Le cours du développement du Nord du Canada a été influencé durant les trente dernières années par la négotiation des revendications territoriales globales. Pendant une grande partie du 20ème siècle, la colonisation et le développement du Nord canadien ont été vécus par les autochtones comme un processus d'empiètement (et quelquefois de transformation) de leurs territoires traditionnels et de restriction de leur mode de vie. L'assèchement, le détournement, la pollution et la contamination des systèmes fluviaux, les restrictions gouvernementales concernant la chasse et la pêche ainsi que le déplacement et la sédentarisation de ces populations en sont quelques exemples. L'action politique et judiciaire des autochtones, dans les années 70, a conduit à l'établissement d'un processus officiel pour la résolution de leurs revendications territoriales et à la révision des interprétations judiciaires de leurs droits authochtones et des traités. Cet article décrit comment des géographes ont contribuéà rendre compte de ces revendications et comment celles-ci ont transformé les régimes d'exploitation du territoire et des ressources du Nord du Canada. En conclusion, quelques observations montrent l'efficacité de ces remèdes et les changements apportés aux perspectives canadiennes au sujet des autochtones de cette région, de l'environnement nordique et du développement du Nord canadien. [source]

Simultaneous Atlantic,Pacific blocking and the Northern Annular Mode

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 636 2008
Tim Woollings
Abstract A synoptic situation termed ,high-latitude blocking' (HLB) is shown to occur frequently in both the Atlantic and Pacific sectors, and to result in flow anomalies very similar to those associated with the negative phase of the Northern Annular Mode (NAM) in the respective sector. There is a weak but significant link between the occurrence of HLB in the two sectors, with Atlantic HLB tending to lead Pacific HLB by 1,3 days. This link arises from rare events in which both sectors are almost simultaneously affected by a large-scale wave-breaking event which distorts the polar trough over Northern Canada. In several cases the tropospheric wave-breaking occurs in tandem with a large-scale disturbance of the stratospheric polar vortex. There is, therefore, a physical link between the Atlantic and Pacific sectors, but analysis suggests that this does not contribute to determining the pattern of the NAM, as conventionally defined from monthly mean data. However, an alternative version of the NAM, derived directly from daily data, does appear to reflect this physical link. These conflicting results highlight the sensitivity of the NAM to the period over which data are averaged. Copyright © 2008 Royal Meteorological Society [source]

Rock albedo and monitoring of thermal conditions in respect of weathering: some expected and some unexpected results

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 7 2005
Kevin Hall
Abstract Broadly speaking, there is, at least within geomorphic circles, a general acceptance that rocks with low albedos will warm both faster and to higher temperatures than rocks with high albedos, reflectivity influencing radiative warming. Upon this foundation are built notions of weathering in respect of the resulting thermal differences, both at the grain scale and at the scale of rock masses. Here, a series of paving bricks painted in 20 per cent reflectivity intervals from black through to white were used to monitor albedo-influenced temperatures at a site in northern Canada in an attempt to test this premise. Temperatures were collected, for five months, for the rock surface and the base of the rock, the blocks being set within a mass of local sediment. Resulting thermal data did indeed show that the dark bricks were warmer than the white but only when their temperatures were equal to or cooler than the air temperature. As brick temperature exceeded that of the air, so the dark and light bricks moved to parity; indeed, the white bricks frequently became warmer than the dark. It is argued that this ,negating' of the albedo influence on heating is a result of the necessity of the bricks, both white and black, to convect heat away to the surrounding cooler air; the darker brick, being hotter, initially convects faster than the white as a product of the temperature difference between the two media. Thus, where the bricks become significantly hotter than the air, they lose energy to that air and so their respective temperatures become closer, the albedo influence being superceded by the requirement to equilibrate with the surrounding air. It is argued that this finding will have importance to our understanding of weathering in general and to our perceptions of weathering differences between different lithologies. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Array-conditioned deconvolution of multiple-component teleseismic recordings

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2010
C.-W. Chen
SUMMARY We investigate the applicability of an array-conditioned deconvolution technique, developed for analysing borehole seismic exploration data, to teleseismic receiver functions and data pre-processing steps for scattered wavefield imaging. This multichannel deconvolution technique constructs an approximate inverse filter to the estimated source signature by solving an overdetermined set of deconvolution equations, using an array of receivers detecting a common source. We find that this technique improves the efficiency and automation of receiver function calculation and data pre-processing workflow. We apply this technique to synthetic experiments and to teleseismic data recorded in a dense array in northern Canada. Our results show that this optimal deconvolution automatically determines and subsequently attenuates the noise from data, enhancing P -to- S converted phases in seismograms with various noise levels. In this context, the array-conditioned deconvolution presents a new, effective and automatic means for processing large amounts of array data, as it does not require any ad-hoc regularization; the regularization is achieved naturally by using the noise present in the array itself. [source]

A reflector at 200 km depth beneath the northwest Pacific

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2001
S. Rost
SUMMARY We present an analysis of precursors to PP produced by underside reflections from discontinuities in the upper mantle beneath the NW Pacific. The events used for this study occur in the western Pacific Rim (New Zealand, Fiji, Tonga, Solomon, New Guinea, Philippine Islands) and are recorded at the short-period Yellowknife Array (YKA) in northern Canada. The source,receiver combination results in PP reflection points which allow us to study the upper mantle structure in a corridor from the Hawaiian Islands to the Kuril subduction zone. To detect the weak precursors in the time window between the P arrival and the PP onset and to identify them as PP underside reflections, special array techniques are used. Our analysis indicates a reflector at a depth of ,200 km beneath the northwestern Pacific. This reflector shows strong topography of some tens of kilometres on length scales of several hundred kilometres, complicating the detection of this reflector in global or regional stacks of seismograms. Different models for the impedance jump across the reflector, the thickness and the possible fine structure of the reflector are modelled using synthetic seismograms and are compared with the data. The thickness of the reflector has to be less than 7 km and the P wave impedance contrast has to be larger than 5.0,6.5 per cent to be detected by this study. This corresponds to a P -velocity jump of ,4 per cent assuming the PREM density model. [source]

Will climate change be beneficial or detrimental to the invasive swede midge in North America?

GLOBAL CHANGE BIOLOGY, Issue 8 2008
Contrasting predictions using climate projections from different general circulation models
Abstract Climate change may dramatically affect the distribution and abundance of organisms. With the world's population size expected to increase significantly during the next 100 years, we need to know how climate change might impact our food production systems. In particular, we need estimates of how future climate might alter the distribution of agricultural pests. We used the climate projections from two general circulation models (GCMs) of global climate, the Canadian Centre for Climate Modelling and Analysis GCM (CGCM2) and the Hadley Centre model (HadCM3), for the A2 and B2 scenarios from the Special Report on Emissions Scenarios in conjunction with a previously published bioclimatic envelope model (BEM) to predict the potential changes in distribution and abundance of the swede midge, Contarinia nasturtii, in North America. The BEM in conjunction with either GCM predicted that C. nasturtii would spread from its current initial invasion in southern Ontario and northwestern New York State into the Canadian prairies, northern Canada, and midwestern United States, but the magnitude of risk depended strongly on the GCM and the scenario used. When the CGCM2 projections were used, the BEM predicted an extensive shift in the location of the midges' climatic envelope through most of Ontario, Quebec, and the maritime and prairie provinces by the 2080s. In the United States, C. nasturtii was predicted to spread to all the Great Lake states, into midwestern states as far south as Colorado, and west into Washington State. When the HadCM3 was applied, southern Ontario, Saskatchewan, and Washington State were not as favourable for C. nasturtii by the 2080s. Indeed, when used with the HadCM3 climate projections, the BEM predicted the virtual disappearance of ,very favourable' regions for C. nasturtii. The CGCM2 projections generally caused the BEM to predict a small increase in the mean number of midge generations throughout the course of the century, whereas, the HadCM3 projections resulted in roughly the same mean number of generations but decreased variance. Predictions of the likely potential of C. nasturtii spatial spread are thus strongly dependent on the source of climate projections. This study illustrates the importance of using multiple GCMs in combination with multiple scenarios when studying the potential for spatial spread of an organism in response to climate change. [source]

Will northern fish populations be in hot water because of climate change?

GLOBAL CHANGE BIOLOGY, Issue 10 2007
SAPNA SHARMA
Abstract Predicted increases in water temperature in response to climate change will have large implications for aquatic ecosystems, such as altering thermal habitat and potential range expansion of fish species. Warmwater fish species, such as smallmouth bass, Micropterus dolomieu, may have access to additional favourable thermal habitat under increased surface-water temperatures, thereby shifting the northern limit of the distribution of the species further north in Canada and potentially negatively impacting native fish communities. We assembled a database of summer surface-water temperatures for over 13 000 lakes across Canada. The database consists of lakes with a variety of physical, chemical and biological properties. We used general linear models to develop a nation-wide maximum lake surface-water temperature model. The model was extended to predict surface-water temperatures suitable to smallmouth bass and under climate-change scenarios. Air temperature, latitude, longitude and sampling time were good predictors of present-day maximum surface-water temperature. We predicted lake surface-water temperatures for July 2100 using three climate-change scenarios. Water temperatures were predicted to increase by as much as 18 °C by 2100, with the greatest increase in northern Canada. Lakes with maximum surface-water temperatures suitable for smallmouth bass populations were spatially identified. Under several climate-change scenarios, we were able to identify lakes that will contain suitable thermal habitat and, therefore, are vulnerable to invasion by smallmouth bass in 2100. This included lakes in the Arctic that were predicted to have suitable thermal habitat by 2100. [source]

Trends in timing of low stream flows in Canada: impact of autocorrelation and long-term persistence

HYDROLOGICAL PROCESSES, Issue 8 2010
Eghbal Ehsanzadeh
Abstract The annual timing of river flows might indicate changes that are climate related. In this study, trends in timing of low flows for the Reference Hydrometric Basin Network were investigated under three different hypotheses namely: independence, short-term persistence (STP) and long-term persistence (LTP). Both summer and winter time series were characterized with scaling behaviour providing strong evidence of LTP. The Mann,Kendall trend test was modified to account for STP and LTP, and used to detect trends in timing of low flows. It was found that considering STP and LTP resulted in a significant decrease in the number of detected trends. Numerical analysis showed that the timing of summer 7-day low flows exhibited significant trends in 16, 9 and 7% of stations under independence, STP and LTP assumptions, respectively. Timing of summer low flow shifted toward later dates in western Canada, whereas the majority of stations in the east half of the country (except Atlantic Provinces) experienced a shift toward earlier dates. Timing of winter low flow experienced significant trends in 20, 12, and 6% of stations under independence, STP and LTP assumptions, respectively. Shift in timing of winter low flow toward earlier dates was dominant all over the country where it shifted toward earlier dates in up to 3/4 of time series with significant trends. There are local patterns of upward significant/insignificant trends in southeast, southwest and northern Canada. This study shows that timing of low flows in Canada is time dependent; however, addressing the full complexity of memory properties (i.e. short term vs long term) of a natural process is beyond the scope of this study. Copyright © 2009 John Wiley & Sons, Ltd. [source]

The role of waves in ice-jam flooding of the Peace-Athabasca Delta

HYDROLOGICAL PROCESSES, Issue 19 2007
Spyros Beltaos
Abstract Since the late 1960s, a paucity of ice-jam flooding in the lower Peace River has resulted in prolonged dry periods and considerable reduction in the area covered by lakes and ponds that provide habitat for aquatic life in the Peace-Athabasca Delta (PAD) region. To identify the causes of this trend, and to develop mitigation or adaptation strategies under present and future climatic conditions, it is necessary to understand the mechanisms that lead to breakup of the ice cover and jamming within the delta reach of Peace River. Because the lower Peace is extremely flat, the long-period waves caused by spring snowmelt are not generally capable of dislodging the winter ice cover, even under conditions of very high flow. The ice cover decays in place and rubble generation, an essential condition for ice jamming, does not occur. However, major jams do, on occasion, form in the middle section of the river and make their way to the delta via repeated releases and stalls. Each release generates a steep wave which can greatly amplify the hydrodynamic forces that are applied on the ice cover and bring about its dislodgment. This is quantified for the lower Peace River by applying recently developed methodology to local hydrometric data. Detailed in situ observations in the spring of 2003, and additional data from 1997 and 2002, fully corroborate this conclusion. Implications to other flat rivers of northern Canada are discussed. Copyright © 2007 Crown in the right of Canada. Published by John Wiley & Sons, Ltd. [source]

Ecosystem properties determined by plant functional group identity

JOURNAL OF ECOLOGY, Issue 2 2010
Jennie R. McLaren
Summary 1.,Ecosystem properties may be determined by the number of different species or groups of species in a community, the identity of those groups, and their relative abundance. The mass ratio theory predicts that the effect of species or groups of species on ecosystem properties will be dependent on their proportional abundance in a community. 2.,Single plant functional groups (graminoids, legumes, non-leguminous forbs) were removed from a natural grassland in northern Canada to examine the role of group identity in determining both ecosystem properties and biomass compensation by remaining species. Removals were conducted across two different environmental treatments (fertilization and fungicide) to examine the context dependency of functional group identity effects. 3.,The degree of biomass compensation in the first 4 years after removal was influenced by the identity of the functional group removed and also of those remaining. When graminoids were removed, none of the remaining functional groups compensated for the loss of biomass. Graminoids partially compensated for the removal of forbs or legumes, with the degree of compensation depending on environmental treatments. 4.,Light interception, soil moisture and soil nutrients were all influenced by functional group identity, with graminoids having a greater impact than expected based on their biomass contribution to the community. Legumes, in contrast, had very little effect on any of the ecosystem properties measured. 5.,For most ecosystem properties measured, the role of plant functional groups was not context dependent; functional groups had the same effect on ecosystem properties regardless of fertilization or fungicide treatments. 6.,Synthesis. We have shown that the effects of losing a functional group do not solely depend on the group's dominance. In this northern grassland, there are greater effects of losing graminoids than one would predict based on their biomass contributions to the community, and functional group identity plays a critical role in determining the effects of diversity loss. [source]

Dynamic photo-inhibition and carbon gain in a C4 and a C3 grass native to high latitudes

PLANT CELL & ENVIRONMENT, Issue 11 2004
D. S. KUBIEN
ABSTRACT C4 plants are rare in the cool climates characteristic of high latitudes and altitudes, perhaps because of an enhanced susceptibility to photo-inhibition at low temperatures relative to C3 species. In the present study we tested the hypothesis that low-temperature photo-inhibition is more detrimental to carbon gain in the C4 grass Muhlenbergia glomerata than the C3 species Calamogrostis Canadensis. These grasses occur together in boreal fens in northern Canada. Plants were grown under cool (14/10 °C day/night) and warm (26/22 °C) temperatures before measurement of the light responses of photosynthesis and chlorophyll fluorescence at different temperatures. Cool growth temperatures led to reduced rates of photosynthesis in M. glomerata at all measurement temperatures, but had a smaller effect on the C3 species. In both species the amount of xanthophyll cycle pigments increased when plants were grown at 14/10 °C, and in M. glomerata the xanthophyll epoxidation state was greatly reduced. The detrimental effect of low growth temperature on photosynthesis in M. glomerata was almost completely reversed by a 24-h exposure to the warm-temperature regime. These data indicate that reversible dynamic photo-inhibition is a strategy by which C4 species may tolerate cool climates and overcome the Rubisco limitation that is prevalent at low temperatures in C4 plants. [source]

Environment, race and nation reconsidered: reflections on Aboriginal land claims in Canada

THE CANADIAN GEOGRAPHER/LE GEOGRAPHE CANADIEN, Issue 4 2003
Peter J. Usher
The course of development in Northern Canada has been transformed in the last 30 years by the comprehensive land claims process. For much of the twentieth century, the settlement and development of northern Canada was experienced by Aboriginal people as a continuing process of encroachment on (and sometimes transformation of) their traditional territories, and of restriction of their customary livelihood. Examples of this process included the alteration of river systems by impoundment and diversion, the pollution and contamination of river systems, government restrictions on hunting and fishing and population relocation and sedentarization. Aboriginal political and legal action led, in the 1970s, to the establishment of a formal process for resolving Aboriginal land claims, and to revised judicial interpretation of Aboriginal and treaty rights. The paper describes how geographers have contributed to documenting those claims, and how land claims settlements have altered the land and resource regimes in northern Canada, and concludes with some observations on the effectiveness of those remedies, and on the changes in Canadian perspectives on Aboriginal northerners, the northern environment and northern development. Le cours du développement du Nord du Canada a été influencé durant les trente dernières années par la négotiation des revendications territoriales globales. Pendant une grande partie du 20ème siècle, la colonisation et le développement du Nord canadien ont été vécus par les autochtones comme un processus d'empiètement (et quelquefois de transformation) de leurs territoires traditionnels et de restriction de leur mode de vie. L'assèchement, le détournement, la pollution et la contamination des systèmes fluviaux, les restrictions gouvernementales concernant la chasse et la pêche ainsi que le déplacement et la sédentarisation de ces populations en sont quelques exemples. L'action politique et judiciaire des autochtones, dans les années 70, a conduit à l'établissement d'un processus officiel pour la résolution de leurs revendications territoriales et à la révision des interprétations judiciaires de leurs droits authochtones et des traités. Cet article décrit comment des géographes ont contribuéà rendre compte de ces revendications et comment celles-ci ont transformé les régimes d'exploitation du territoire et des ressources du Nord du Canada. En conclusion, quelques observations montrent l'efficacité de ces remèdes et les changements apportés aux perspectives canadiennes au sujet des autochtones de cette région, de l'environnement nordique et du développement du Nord canadien. [source]

Dynamics of reintroduction in an indigenous large ungulate: the wood bison of northern Canada

ANIMAL CONSERVATION, Issue 4 2000
N. C. Larter
We document the recolonization of an indigenous large herbivore into its historic range. Eighteen wood bison (Bison bison athabascae) were reintroduced into the Mackenzie Bison Sanctuary of the Northwest Territories, Canada, in 1963. The population subsequently increased in number and range, peaking at about 2400 in 1989; numbers were estimated at about 1900 in 1998. Recolonization occurred through a series of increases in local areas followed by pulses of dispersal and range expansion. This pattern was originally described for exotic species' introductions. Differences in diet and overwinter survival of calves over the bison's range suggest that intraspecific competition for food provided the stimulus for range expansion. For a conservation strategy, the reintroduction of animals into several independent sites in their historic range would facilitate recolonization and achieve a faster spread than a reintroduction into one site followed by waiting for the population to spread as a result of its own density dependent responses. [source]

SUNRISE , Impressions from a successful science flight

ASTRONOMISCHE NACHRICHTEN, Issue 6 2010
W. Schmidt
Abstract SUNRISE is a balloon-borne telescope with an aperture of one meter. It is equipped with a filter imager for the UV wavelength range between 214 nm and 400 nm (SUFI), and with a spectro-polarimeter that measures the magnetic field of the photosphere using the Fe I line at 525.02 nm that has a Landé factor of 3. SUNRISE performed its first science flight from 8 to 14 June 2009. It was launched at the Swedish ESRANGE Space Center and cruised at an altitude of about 36 km and geographic latitudes between 70 and 74 degrees to Somerset Island in northern Canada. There, all data, the telescope and the gondola were successfully recovered. During its flight, Sunrise achieved high pointing stability during 33 hours, and recorded about 1.8 TB of science data. Already at this early stage of data processing it is clear that SUNRISE recorded UV images of the solar photosphere, and spectropolarimetric measurements of the quiet Sun's magnetic field of unprecedented quality (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]