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| 3. |
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| 4. |
- Fisher, D., et al.
(author)
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The Mt Logan Holocene-late Wisconsinan isotope record : Tropical Pacific-Yukon connections
- 2008
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In: Holocene. - : SAGE Publications. ; 18:5, s. 667-677
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Journal article (peer-reviewed)abstract
- The ice core recovered from Prospector Russell Col on Mt Logan (5.4 km a.s.l.), in the Yukon spans over 20 000 years. This unique record offers a Pacific view of the stable isotope and chemical record from the Lateglacial to the present. The timescale is based on seasonal counted years, the largest known volcanic acid signatures and the major shift in stable isotopes and chemistry at the end of the Younger Dryas. There are large and sustained changes in the stable isotopic record that are anti-correlated with marine and continental chemistry series. The oxygen-18 in this area is not a proxy for palaeotemperature but rather for source region. The last major isotope shift in AD 1840 in δ(18O) and chemistry is compared with the Quinn's ENSO record. During periods of more frequent La Niña (stronger tropical easterlies) there is more zonal flow of water vapour transport to the Pacific Northwest, δ(18O) values are larger and the deuterium excess d smaller. These periods coincide with periods of lower accumulation/precipitation in southern Yukon. The Holocene δ(18O) record indicates many large shifts between the meridional (strong El Niño) and zonal (La Niña). Comparison of the Logan isotopic record and the moisture/temperature-sensitive time series of peat bog inception dates for the Northwest shows a strong correlation (0.36) that points to high accumulation rates coincident with low δ(18O) and enhanced meridional flow. Major changes in the core at 4200 BP and 7000—8000 BP point to enhanced meridional flow, which coincide with big changes in the Pacific palaeorecords of the balance between El Niño and La Niña. 4200 BP seems to have inaugurated the `modern' ENSO world.
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| 7. |
- Foy, N., et al.
(author)
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Recent volume and area changes of Kaskawulsh Glacier, Yukon, Canada
- 2011
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In: Journal of Glaciology. - : International Glaciological Society. - 0022-1430 .- 1727-5652. ; 57:203, s. 515-525
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Journal article (peer-reviewed)abstract
- Recent surface elevation changes of Kaskawulsh Glacier, Yukon, Canada, are quantified by comparing an air-photo derived DEM from 1977 and airborne lidar measurements from 1995, 2000 and 2007. Surface-area changes are assessed using historical aerial photography from 1956 and satellite imagery from 1977 to 2007. Combined, these measurements provide some of the first detailed records of volume change of a large Yukon glacier. Between 1977 and 2007, Kaskawulsh Glacier underwent a decrease in area of 1.53% and a decrease in volume of 3.27–5.94 km3 w.e.). The terminus also retreated by 655 m over the period 1956–2007. There was relatively minor volume change over the period 1977–95 (<+0.01 km3 w.e.a−1), while over the periods 1995–2000 and 2000–07 volume losses occurred at a relatively constant rate of −0.51 and −0.50 km3 a−1 w.e., respectively. Since 1995, thinning has been prominent throughout the ablation zone, while relative stability and even slight thickening has occurred in the accumulation zone. These findings are similar to those recently observed at other nearby Alaskan glaciers.
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| 13. |
- Zdanowicz, Christian M., et al.
(author)
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A Holocene record of atmospheric dust deposition on the Penny ice cap, Baffin Island, Canada
- 2000
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In: Quaternary Research. - : Cambridge University Press (CUP). - 0033-5894 .- 1096-0287. ; 53:1, s. 62-69
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Journal article (peer-reviewed)abstract
- An >11,550-yr-long record of atmospheric dust deposition was developed from an ice core (P95) drilled through the Penny ice cap, Baffin Island. The P95 record documents environmental changes that affected the production and transport of dust in the eastern Canadian Arctic during the late Pleistocene and Holocene. Dust deposition on the Penny ice cap was greatest in late-glacial time when the climate was dry and windy and comparatively low in the Holocene. Microparticles deposited during late-glacial time are finer than in Greenland cores, suggesting distinct dust sources and transport trajectories to each region. Dust deposition at the P95 site increased after ca. 7800 yr ago as the Penny ice cap receded and distance from local dust sources was reduced. Deflation of newly exposed marine sediments on southwestern Baffin Island may have contributed to this dust increase. The P95 and GISP2 (Greenland) dust records show diverging trends in the middle to late Holocene, reflecting the growing influence of regional environmental conditions (e.g., dust source area, snow cover extent) on atmospheric dust deposition. This study further demonstrates how valuable records of regional-scale paleoenvironmental changes can be developed from small circum-Arctic ice caps, even those affected by considerable melt.
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| 14. |
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| 15. |
- Zdanowicz, Christian M., et al.
(author)
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Metal emissions from a Cu smelter, Rouyn-Noranda, Quebec: Characterization of particles sampled in air and snow
- 2006
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In: Geochemistry: Exploration, Environment, Analysis. - : Geological Society of London. - 1467-7873 .- 2041-4943. ; 6:2-3, s. 147-162
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Journal article (peer-reviewed)abstract
- Particles were sampled in air and snow near a Cu smelter inRouyn-Noranda, Québec, as part of a study of airborne metal emissions. An analytical scanning electron microscope (SEM) was used to measure the size and elemental composition of >38 000 individual particles. Metal-bearing (Me-) particles account for c. 58% of all particles in the smelter plume, but only c. 15% in ambient air or snow. The dominant Me-particle type in snow is Fe–S–Cu but Zn–S, Fe–S, and Cu–S are also common. Pb is dominant in air-filtered particles, even those collected far (>60 km) from the smelter. Me-particles in snow are compositionally more variable and complex than in the smelter plume or ambient air, suggesting that Me-particles settling from the plume in snow are chemically transformed in the process, possibly by heterogeneous reaction(s) with other aerosols (e.g. salt particles) and/or gases (e.g. SO2). The size distribution of Me-particles in the smelter plume is broader than in snow or ambient air, owing to a larger proportion of sub-micrometre particles in the plume and/or the loss of fine water-soluble Me-particles in snow meltwater. However, the size distribution of different Me-particle groupings (e.g. As-bearing compared to Cd-bearing particles) is notsignificantly different within the size range measured.
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| 16. |
- Zdanowicz, Christian M., et al.
(author)
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Mount Mazama eruption: Calendrical age verified and atmospheric impact assessed
- 1999
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In: Geology. ; 27:7, s. 621-624
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Journal article (peer-reviewed)abstract
- Geochemical identification of Mount Mazama ash in the Greenland Ice Sheet Project 2(GISP2) ice core gives a calendrical age of 7627 ± 150 cal yr B.P. (5677 ± 150 B.C.) for the erup- tion, thus providing a more accurate early Holocene stratigraphic time line than previously available. The GISP2 record of volcanically derived sulfate suggests a total stratospheric aerosol loading between 88 and 224 Mt spread over an ~6 yr period following the eruption of Mount Mazama. Taking into account the likelihood of some tropospheric aerosol transport to Green- land, realistic estimates of the resulting atmospheric optical depth range from 0.6 to 1.5. These values may have produced a temperature depression of ~0.6 to 0.7 °C at mid to high northern latitudes for 1–3 yr after the eruption. These results indicate that the 5677 B.C. eruption of Mount Mazama was one of the most climatically significant volcanic events of the Holocene in the Northern Hemisphere. We also calculate a maximum stratospheric Cl– release of 8.1 Mt bythe eruption, which may have led to substantial stratospheric ozone depletion.
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| 17. |
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| 18. |
- Andin, Caroline, et al.
(author)
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Synoptic variability of extreme snowfall in the St. Elias Mountains,Yukon, Canada
- 2015
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Conference paper (peer-reviewed)abstract
- Glaciers in the Wrangell and St. Elias Mountains (Alaska and Yukon) are presently experiencing some of thehighest regional wastage rates worldwide. While the effect of regional temperatures on glacier melt rates in thisregion has been investigated, comparatively little is known about how synoptic climate variations, for example inthe position and strength of the Aleutian Low, modulate snow accumulation on these glaciers. Such informationis needed to accurately forecast future wastage rates, glacier-water resource availability, and contributions tosea-level rise. Starting in 2000, automated weather stations (AWS) were established in the central St-EliasMountains (Yukon) at altitudes ranging from 1190 to 5400 m asl, to collect climatological data in support ofglaciological research. These data are the longest continuous year-round observations of surface climate everobtained from this vast glaciated region. Here we present an analysis of snowfall events in the icefields of theSt-Elias Mountains based on a decade-long series of AWS observations of snow accumulation. Specifically,we investigated the synoptic patterns and air mass trajectories associated with the largest snowfall events (> 25cm/12 hours) that occurred between 2002 and 2012. Nearly 80% of these events occurred during the cold season(October-March), and in 74 % of cases the precipitating air masses originated from the North Pacific south of50N. Zonal air mass advection over Alaska, or from the Bering Sea or the Arctic Ocean, was comparativelyrare (20%). Somewhat counter-intuitively, dominant surface winds in the St. Elias Mountains during highsnowfall events were predominantly easterly, probably due to boundary-layer frictional drag and topographicfunneling effects. Composite maps of sea-level pressure and 700 mb winds reveal that intense snowfall eventsbetween 2002 and 2012 were associated with synoptic situations characterized by a split, eastwardly-shifted orlongitudinally-stretched Aleutian Low (AL) having an easternmost node near the Kenai Peninsula, conditionsthat drove a strong southwesterly upper airstream across the Gulf of Alaska towards the coast. Situations with asingle-node, westerly-shifted AL were comparatively rare. The spatial configuration of the synoptic AL pressurepattern appears to play a greater role in determining snowfall amount in the central St. Elias Mountains than dopressure anomalies within the AL. The estimated snowfall gradient from coastal Alaska to the central St. EliasMountains during intense snowfall events averaged +2.0 0.7 mm/km (SWE), while the continental-side gradientfrom the mountains towards the Yukon plateau averaged -3.3 0.9 mm/km (SWE). The findings presented herecan better constrain the climatic interpretation of long proxy records of snow accumulation variations developedfrom glacier cores drilled in the St. Elias Mountains or nearby regions.
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| 19. |
- Beal, Samuel A., et al.
(author)
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Ice Core Perspective on Mercury Pollution during the Past 600 Years
- 2015
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In: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 49:13, s. 7641-7647
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Journal article (peer-reviewed)abstract
- Past emissions of the toxic metal mercury (Fig) persist in the global environment yet these emissions remain poorly constrained by existing data. Ice cores are high-resolution archives of atmospheric deposition that may provide crucial insight into past atmospheric Hg levels during recent and historical time. Here we present a record of total Hg (Hg-T) in an ice core from the pristine summit plateau (5340 m asl) of Mount Logan, Yukon, Canada, representing atmospheric deposition from AD 1410 to 1998. The Colonial Period (similar to 1603-1850) and North American "Gold Rush" (1850-1900) represent minor fractions (8% and 14%, respectively) of total anthropogenic Hg deposition in the record, with the majority (78%) occurring during the 20th Century. A period of maximum HgT fluxes from 1940 to 1975 coincides with estimates of enhanced anthropogenic Hg emissions from commercial sources, as well as with industrial emissions of other toxic metals. Rapid declines in HgT fluxes following peaks during the Gold Rush and the mid-20th Century indicate that atmospheric Hg deposition responds quickly to reductions in emissions. Increasing HgT fluxes from 1993 until the youngest samples in 1998 may reflect the resurgence of Hg emissions from unregulated coal burning and small-scale gold mining.
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| 20. |
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| 21. |
- Beaudoin, Anne, et al.
(author)
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Paleoenvironmental reconstructions of Nettilling Lake area (Baffin Island, Nunavut) : A multi-proxy analysis
- 2014
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Conference paper (peer-reviewed)abstract
- The paleoclimate and paleolimnological history of several Arctic regions remains poorly known. This is the casefor the area around Nettilling Lake (Baffin Island, Nunavut), the largest lake of the Canadian Arctic Archipelago.To reconstruct the past environmental history of this area, a highly innovative multi-proxy approach combiningphysical, magnetic, chemical and biological properties preserved in lake sediments was used. One particular goalof this study was to investigate the possible coupling between sedimentation processes observed in the lake andmelt rates of nearby Penny Ice Cap.A 1-m long sediment core was retrieved from a small bay in the northeastern part of Nettilling Lake duringthe summer of 2010. This sampling area was chosen based on the hypothesis that incoming glacial meltwatersfrom Penny Ice Cap would leave a strong climate-modulated signal that would be reflected in the sedimentarysequence. The core was analyzed by both non-destructive (X-radiography (X-ray), microfluorescence-X (-XRF),magnetic susceptibility) and destructive (Loss On Ignition, grain size, water content, thin sections, diatoms)techniques. Radiometric AMS 14C and 210Pb/137Cs age determinations, as well as paleomagnetic measurements,were used to develop the core chronology, yielding an estimated bottom age of approximately 1365 AD.The sedimentation rate (0.15 cm.yr-1) in Nettilling Lake was found to be high compared to other Arctic lakes,due to inputs of highly turbid meltwaters from Penny Ice Cap with high suspended sediment loads. Significantcorrelations were found between geochemical profiles of elements linked to detrital inputs (Si, Ti, K, Ca) and meltrates from Penny Ice Cap since the 19th century. This suggests that variations in detrital elements in NettillingLake sediments might be used as an indirect indicator of regional climate fluctuations (e.g., summer temperatures) that determine glacier melt rates.
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| 22. |
- Cosgrove, Christopher, et al.
(author)
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Environmental controls on snow water equivalent in two sub-Arctic mountain catchments
- 2013
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Conference paper (other academic/artistic)abstract
- Spatial variability of seasonal snow depth poses a challenge when estimating snow water equivalent (SWE) from in-situ measurements in mountainous areas. Poor accessibility, complex topographic effects and localized microclimates make extrapolation of in-situ SWE measurements to a basin scale difficult. Remotely-sensed passive microwave SWE products are also inaccurate in complex terrain and/or at the forest-alpine tundra transition zone. To address these caveats, we investigated the relative importance of landscape qualities (altitude, slope, aspect, vegetation) and climate (winter temperatures, precipitation) on SWE distribution in two sub-Arctic mountainous catchments in Hemavan, Sweden, and Wolf Creek, Yukon, Canada. The two catchments are comparable, but have contrasted climate regimes. In-situ SWE measurements were made in March-April 2014 across the forest-tundra ecotone in both catchments. These were supplemented with historical snow-survey data since 2012 in Hemavan, and 1993 in Wolf Creek. Pairwise linear regressions of SWE against different landscape factors indicate that overall, altitude exerts the largest control on SWE at both Hemavan and Wolf Creek, but its effect is lesser within individual vegetation zones. In other respects, the two sites differ. SWE is inversely correlated to surface slope at forested sites in Hemavan (R^2 = 0.57, p = 0.25), but not in Wolf Creek. Slope aspect is positively correlated with SWE at forest-tundra transition sites (R^2 = 0.49, p = 0.12) in Wolf Creek, but not in Hemavan. For alpine tundra sites, slope angle strongly influences SWE in Hemavan (R^2 = 0.58, p = 0.24), but only weakly in Wolf Creek (R^2 = 0.05, p = 0.71). We discuss possible causes of these inter-catchment differences, and also evaluate the effect of inter-annual climate variations on SWE distribution at Wolf Creek using the long-term snow-survey record. Finally, we compare and discuss SWE estimates obtained by three different field measurement methods.
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| 23. |
- Dastoor, Ashu, et al.
(author)
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Arctic mercury cycling
- 2022
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In: Nature Reviews Earth & Environment. - : Springer Nature. - 2662-138X. ; 3:4, s. 270-286
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Research review (peer-reviewed)abstract
- Anthropogenic mercury (Hg) emissions have driven marked increases in Arctic Hg levels,which are now being impacted by regional warming, with uncertain ecological consequences. This Review presents a comprehensive assessment of the present-day total Hg mass balance in the Arctic. Over 98% of atmospheric Hg is emitted outside the region and is transported to the Arctic via long-range air and ocean transport. Around two thirds of this Hg is deposited in terrestrial ecosystems, where it predominantly accumulates in soils via vegetation uptake. Rivers and coastal erosion transfer about 80 Mg year−1 of terrestrial Hg to the Arctic Ocean, in approximate balance with modelled net terrestrial Hg deposition in the region. The revised Arctic Ocean Hg mass balance suggests net atmospheric Hg deposition to the ocean and that Hg burial in inner-shelf sediments is underestimated (up to >100%), needing seasonal observations of sediment-oceanHg exchange. Terrestrial Hg mobilization pathways from soils and the cryosphere (permafrost, ice, snow and glaciers) remain uncertain. Improved soil, snowpack and glacial Hg inventories, transfer mechanisms of riverine Hg releases under accelerated glacier and soil thaw, coupled atmosphere– terrestrial modelling and monitoring of Hg in sensitive ecosystems such as fjords can help toanticipate impacts on downstream Arctic ecosystems.
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| 24. |
- Fisher, D. A., et al.
(author)
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The effects of flowline length evolution on chemistry - δ18O profiles from Penny Ice Cap, Baffin Island, Canada
- 2002
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In: Annals of Glaciology. - : International Glaciological Society. - 0260-3055 .- 1727-5644. ; 35:1, s. 150-156
-
Journal article (peer-reviewed)abstract
- The isotopic and chemical signatures for ice-age and Holocene ice from Summit, Greenland, and Penny Ice Cap, Baffin Island, Canada, are compared. The usual pattern of low δ180, 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's flowlines all start close to the present site. The Penny Ice Cap early-Holocene δ180's had to be corrected to offset the Laurentide meltwater distortion.The analysis suggests that presently the Summit and Penny Ice Cap marine impurity ori ginates about 500 km away, and that presently Penny Ice Cap receives a significant amountoflocal continental impurity.
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| 25. |
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| 26. |
- Gamberg, Mary, et al.
(author)
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Mercury in the Canadian Arctic Terrestrial Environment : An Update
- 2015
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In: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 509-510, s. 28-40
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Journal article (peer-reviewed)abstract
- Contaminants in the Canadian Arctic have been studied over the last twenty years under the guidance of the Northern Contaminants Program. This paper provides the current state of knowledge on mercury (Hg) in theCanadian Arctic terrestrial environment. Snow, ice, and soils on land are key reservoirs for atmospheric deposition and can become sources of Hg through the melting of terrestrial ice and snow and via soil erosion. In the Canadian Arctic, new data have been collected for snow and ice that provide more information on the net accumulation and storage of Hg in the cryosphere. Concentrations of total Hg (THg) in terrestrial snow are highly variable but on average, relatively low (less than 5ng/L), and methylmercury (MeHg) levels in terrestrial snow are also generally low (less than 0.1 ng/L). On average, THg concentrations in snow on Canadian Arctic glaciers are muchlower than those reported on terrestrial lowlands or sea ice. Hg in snow may be affected by photochemical exchanges with the atmosphere mediated by marine aerosols and halogens, and by post-depositional redistribution within the snow pack. Regional accumulation rates of THg in Canadian Arctic glaciers varied little during the past century but show evidence of an increasing north-to-south gradient. Temporal trends of THg in glacier cores indicate an abrupt increase inthe early 1990s, possibly due to volcanic emissions, followed by more stable, but relatively elevated levels. Little information is available on Hg concentrations and processes in Arctic soils. Terrestrial Arctic wildlife typically have low levels of THg (less than μg/g dry weight) in their tissues, although caribou(Rangifer tarandus) can have higher Hg because they consume large amounts of lichen.THg concentrations in the Yukon’s Porcupine caribou herd vary among years but there has been no significant increase or decrease over the last two decades.
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| 27. |
- Keuschnig, Christoph, et al.
(author)
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Selection processes of Arctic seasonal glacier snowpack bacterial communities
- 2023
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In: Microbiome. - : BioMed Central (BMC). - 2049-2618. ; 11:1
-
Journal article (peer-reviewed)abstract
- BackgroundArctic snowpack microbial communities are continually subject to dynamic chemical and microbial input from the atmosphere. As such, the factors that contribute to structuring their microbial communities are complex and have yet to be completely resolved. These snowpack communities can be used to evaluate whether they fit niche-based or neutral assembly theories.MethodsWe sampled snow from 22 glacier sites on 7 glaciers across Svalbard in April during the maximum snow accumulation period and prior to the melt period to evaluate the factors that drive snowpack metataxonomy. These snowpacks were seasonal, accumulating in early winter on bare ice and firn and completely melting out in autumn. Using a Bayesian fitting strategy to evaluate Hubbell’s Unified Neutral Theory of Biodiversity at multiple sites, we tested for neutrality and defined immigration rates at different taxonomic levels. Bacterial abundance and diversity were measured and the amount of potential ice-nucleating bacteria was calculated. The chemical composition (anions, cations, organic acids) and particulate impurity load (elemental and organic carbon) of the winter and spring snowpack were also characterized. We used these data in addition to geographical information to assess possible niche-based effects on snow microbial communities using multivariate and variable partitioning analysis.ResultsWhile certain taxonomic signals were found to fit the neutral assembly model, clear evidence of niche-based selection was observed at most sites. Inorganic chemistry was not linked directly to diversity, but helped to identify predominant colonization sources and predict microbial abundance, which was tightly linked to sea spray. Organic acids were the most significant predictors of microbial diversity. At low organic acid concentrations, the snow microbial structure represented the seeding community closely, and evolved away from it at higher organic acid concentrations, with concomitant increases in bacterial numbers.ConclusionsThese results indicate that environmental selection plays a significant role in structuring snow microbial communities and that future studies should focus on activity and growth.
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| 28. |
- Kinnard, C., et al.
(author)
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Calibration of an ice-core glaciochemical (sea-salt) record with sea-ice variability in the Canadian Arctic
- 2006
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In: Annals of Glaciology. - : International Glaciological Society. - 0260-3055 .- 1727-5644. ; 44, s. 383-390
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Journal article (peer-reviewed)abstract
- Correlation between glaciochemical time Series from an ice core collected on Devon Ice Cap, Nunavut, Canada, and gridded time Series of Sea-ice concentrations reveals Statistically Significant inverse relationships between Sea-salt concentrations (mainly Na+, Mg2+ and Cl–) in the ice core and Sea-ice cover in Baffin Bay over the period 1980–97. An empirical orthogonal function (Eof) analysis performed on all major ions Shows that the dominant mode of glaciochemical variability (Eof1) represents a Sea-salt Signal, which correlates best with Sea-ice concentration in Baffin Bay. On a Seasonal basis, the Strongest and most Spatially extensive anticorrelations are found in Baffin Bay during the fall, followed by Spring, Summer and winter. These results Support the notion that increased open-water conditions in Baffin Bay during the Stormy Seasons (fall and Spring) promote increased production, transport and deposition of Sea-salt aerosols on Devon Ice Cap. Comparison of ice-core time Series of Eof1, δ18O and melt percentage, with air temperatures recorded in Upernavik, Greenland, Suggests that ice-cover variations in Baffin Bay over the past ∽145 years were dynamically rather than thermodynamically controlled, with periods of Strengthened cyclonic circulation leading to increased open-water conditions, and a greater Sea-salt flux on Devon Ice Cap.
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| 29. |
- Kinnard, C., et al.
(author)
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Climatic analysis of sea-ice variability in the Canadian Arctic from operational charts, 1980-2004
- 2006
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In: Annals of Glaciology. - : International Glaciological Society. - 0260-3055 .- 1727-5644. ; 44, s. 391-402
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Journal article (peer-reviewed)abstract
- We present a complete climatic analysis of Sea-ice conditions in the Canadian Arctic based on digitized operational charts from the Canadian Ice Service for the period 1980–2004. The Seasonal climatology, Spatial variance and linear trends in total ice concentrations (CT) were calculated. The maximum reduction rate in CT was found in the Beaufort Sea (>24% decade–1) and in the Davis Strait/Labrador Sea region (>18% decade–1) during Spring and Summer. Empirical orthogonal function (EOF) analysis performed on monthly CT deviations yielded four Significant EOF modes explaining 32% of the total variance. The Spatial pattern, temporal behaviour and Seasonality of these four EOF modes are discussed and correlated with fields of Sea-level pressure, Surface winds, Surface air temperature and Sea-surface temperature monthly anomalies. These results point to the dominant influence of the North Atlantic Oscillation on CT decadal anomalies during the cold Season, while climate variability in the Pacific influences CT variations in the Beaufort Sea region during Spring–summer.
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| 30. |
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| 31. |
- Lacelle, D., et al.
(author)
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Nature and origin of a Pleistocene-age massive ground-ice body exposed in the Chapman Lake moraine complex, central Yukon Territory, Canada
- 2007
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In: Quaternary Research. - : Cambridge University Press (CUP). - 0033-5894 .- 1096-0287. ; 68:2, s. 249-260
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Journal article (peer-reviewed)abstract
- A massive ground-ice body was found exposed in the headwall of a thaw flow developed within the Chapman Lake terminal moraine complex on the Blackstone Plateau (Ogilvie Mountains, central Yukon Territory), which is contemporaneous to the Reid glaciation. Based on visible cryostructures in the 4-m-high headwall, two units were identified: massive ground ice, overlain sharply by 2 m of icy diamicton. The nature and origin of the Chapman Lake massive ground ice was determined using cryostratigraphy, petrography, stable O–H isotopes and the molar concentration of occluded gases (CO2, O2, N2 and Ar) entrapped in the ice, a new technique in the field of periglacial geomorphology that allows to distinguish between glacial and non-glacial intrasedimental ice. Collectively, the results indicate that the Chapman Lake massive ground ice formed by firn densification with limited melting–refreezing and underwent deformation near its margin. Given that the massive ground-ice body consists of relict glacier ice, it suggests that permafrost persisted, at least locally, on plateau areas in the central Yukon Territory since the middle Pleistocene. In addition, the d value of Chapman Lake relict glacier ice suggests that the ice covering the area during the Reid glaciation originated from a local alpine glaciation in the Ogilvie Mountains.
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| 32. |
- Løkkegaard, Anja, et al.
(author)
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Greenland and Canadian Arctic ice temperature profiles database
- 2023
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In: The Cryosphere. - : Copernicus Publications. - 1994-0416 .- 1994-0424. ; 17:9, s. 3829-3845
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Journal article (peer-reviewed)abstract
- Here, we present a compilation of 95 ice temperature profiles from 85 boreholes from the Greenland ice sheet and peripheral ice caps, as well as local ice caps in the Canadian Arctic. Profiles from only 31 boreholes (36 %) were previously available in open-access data repositories. The remaining 54 borehole profiles (64 %) are being made digitally available here for the first time. These newly available profiles, which are associated with pre-2010 boreholes, have been submitted by community members or digitized from published graphics and/or data tables. All 95 profiles are now made available in both absolute (meters) and normalized (0 to 1 ice thickness) depth scales and are accompanied by extensive metadata. These metadata include a transparent description of data provenance. The ice temperature profiles span 70 years, with the earliest profile being from 1950 at Camp VI, West Greenland. To highlight the value of this database in evaluating ice flow simulations, we compare the ice temperature profiles from the Greenland ice sheet with an ice flow simulation by the Parallel Ice Sheet Model (PISM). We find a cold bias in modeled near-surface ice temperatures within the ablation area, a warm bias in modeled basal ice temperatures at inland cold-bedded sites, and an apparent underestimation of deformational heating in high-strain settings. These biases provide process level insight on simulated ice temperatures.
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| 33. |
- Zdanowicz, Christian M., et al.
(author)
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An ice-marginal δ18O record from Barnes Ice Cap, Baffin Island, Canada
- 2002
-
In: Annals of Glaciology. - : International Glaciological Society. - 0260-3055 .- 1727-5644. ; 35:1, s. 145-149
-
Journal article (peer-reviewed)abstract
- Barnes Ice Cap, Baffin Island, Canada, is a remnant of the Laurentide ice sheet that separated from it about 8500 years ago. Owing to recession of the ice cap during the Holocene, Pleistocene-age ice is now exposed along the margin in a distinctive bubble-rich white band. δ180 variations across the white ice resemble those in Canadian Arctic ice cores, suggesting that Barnes Ice Cap preserves a climatic record through thelast glacial period, possibly reaching back into the previous (Sangamon) interglacial. The δ180 shift at the Wisconsin-Holocene transition (15 per mil) exceeds that in other Canadian and Greenland records and cannot be explained solely in climatic terms. A steady-state model reconstruction of the Laurentide ice sheet during the Last Glacial Maximum suggests that Late-glacial strata in Barnes Ice Cap originated high up ( >2400 m a.s.l.) and far "inland" on the ice sheet, along a ridge that extended between the ancestral Foxe and Keewatin ice domes.
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| 34. |
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| 35. |
- Zdanowicz, Christian M., et al.
(author)
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Characteristics of modern atmospheric dust deposition in snow on the Penny Ice Cap, Baffin Island, Arctic Canada
- 1998
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In: Tellus, Series B: Chemical and Physical Meteorology. ; 50:5, s. 506-520
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Journal article (peer-reviewed)abstract
- We evaluated the concentration, size and distribution of insoluble dust microparticles in snow-pits on the Penny Ice Cap (PIC), Ba n Island, to define ( 1) the characteristics of modern atmospheric dust deposition at the site, (2 ) the relative contributions of proximal and distal dust sources, and ( 3) the e ects of summer melting on depositional signals in snow. The mean concentration ( 143 mg kg−1), flux (4.8 mg cm2 yr−1) and diameter (2.3 mm) of dust deposited on the PIC are similar to those observed in remote Arctic sites such as central Greenland, implying that dust is primarily supplied through long-range transport from far-removed source regions (at least 100–1000 km distant). There is evidence for two seasonal maxima of dust deposition, one in late winter-early spring and one in late summer-early fall, although seasonal signals can not always be resolved in the snowpack due to some post-depositional particle migration with summer melt. However, ice layers appear to limit the mobility of particles, thereby preserving valuable paleoclimatic information in the PIC ice core dust record at a multi-annual to decadaltemporal resolution.
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| 36. |
- Zdanowicz, Christian M., et al.
(author)
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Historical variations of mercury stable isotope ratios in arctic glacier firn and ice cores
- 2016
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In: Global Biogeochemical Cycles. - 0886-6236 .- 1944-9224. ; 30:9, s. 1324-1347
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Journal article (peer-reviewed)abstract
- The concentration and isotopic composition of mercury (Hg) were determined in glacier core samples from Canadian Arctic ice caps dating from pre-industrial to recent time (early 21st century). Mean Hg levels increased from ≤ 0.2 ng L-1 in pre-industrial time to ~0.8-1.2 ng L-1 in the modern industrial era (last ~200 years). Hg accumulated on Arctic ice caps has D199Hg and D201Hg that are higher (~-1 to 2.9 ‰) than previously reported for Arctic snow (mostly < -1 ‰) impacted by atmospheric Hg depletion events, suggesting that these events contribute little to Hg accumulation on ice caps. The range of d202Hg, D199Hg and D201Hg in glacier cores overlaps with that of Arctic Hg0(g) and of seawater in Baffin Bay, but also with that of mid-latitude precipitation and industrial Hg sources, including coal and Hg ores. A core from Agassiz ice cap (80.7 °N) shows a ~+1 ‰ shift in d202Hg over the 19th-20th centuries that could reflect changes in the isotopic composition of the atmospheric Hg pool in the High Arctic in response to growing industrial emissions at lower latitudes. This study is the first ever to report on historical variations of Hg stable isotope ratios in Arctic ice cores. Results could help constrain future modeling efforts of the global Hg biogeochemical cycle and the atmosphere's response to changing Hg emissions, past and future.
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