| 1. |
- Zdanowicz, Christian, et al.
(författare)
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Basal debris entrainment and transport in glaciers of southwestern Bylot Island, Canadian Arctic
- 1996
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Ingår i: Annals of Glaciology. - 0260-3055 .- 1727-5644. ; 22:1, s. 107-113
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Tidskriftsartikel (refereegranskat)abstract
- ABSTRACT. Glaciers on southwestern Bylot Island in the Canadian Arctic flow from an alpine setting in high-grade crystalline Archean terrane, on to coastal lowlands underlain by clastic sedimentary strata of Cretaceous to Tertiary age. We have used the contrasting mineralogy of the substrate as a tool to study subglacialentrainment and transport of debris in two large piedmont glaciers on Bylot Island. High chlorite/ and mica-illite/smectite ratios indicate that most basal debris is derived from crystalline rocks underlying the upper reaches of the glaciers. The subglacial accretion of Cretaceous-Tertiary sediments appears restricted to the lowermost part ofthe basal zone and is most noticeable near the glaciers' termini. lce associated with discrete silty-sandy debris layers is characterized by an isotopic signature indicative of refreezing of meltwater at the glacier sole. The compositional, textural and isotopic characteristics of basal sediment and ice lead us to conclude that subglacial entrainment through basal ice accretion occurs in both the upper and marginal parts of the glaciers
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| 2. |
- Zdanowicz, Christian M., et al.
(författare)
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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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Ingår i: Tellus, Series B: Chemical and Physical Meteorology. ; 50:5, s. 506-520
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Tidskriftsartikel (refereegranskat)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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| 3. |
- Zdanowicz, Christian M., et al.
(författare)
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Mount Mazama eruption: Calendrical age verified and atmospheric impact assessed
- 1999
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Ingår i: Geology. ; 27:7, s. 621-624
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Tidskriftsartikel (refereegranskat)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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