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11.
NOAA-AVHRR satellite data have been used for a multi-year analysis of the seasonal variation of snow cover on the peninsula of Jameson Land located from 70°30'N to 72°N on the eastern coast of Greenland. Monitoring programmes for muskoxen and geese populations in Jameson Land wert started in the early 1980s to assess the impact of oil exploration in the area. This study was conducted to provide snow cover data to the wildlife monitoring programmes because snow cover is an important factor which can affect the numbers and distribution of muskoxen and other wildlife in the area.
Snow cover mapping is based on the geometric correction and radiometric calibration of each satellite scene before the visual bands are corrected for the terrain-effects and high solar zenith angle by using a simple radiation model. The atmospheric effect on the thermal infrared bands is corrected by using the "split-window" method. An automatic filtering routine with empirically determined thresholds is used to determine cloud-and haze-covered areas before the snow cover is computed from a linear expression using albedos of bare ground and full snow cover. By combining the satellite information with ground measurements and a digital terrain model, both the spatial distribution of snow cover and the total snow cover depletion can be obtained.
The method makes it possible to analyse the variation in regional and seasonal snow cover in wildlife habitats. The variation in snow cover depletion has been analysed in five subareas in the muskox area, and the results indicate that the snow cover pattern is an important factor which influences muskox calf crop and regional distribution of the muskox population. The method has proved useful for monitoring the duration of snow cover, and its application ought to facilitate the future study of wildlife habitats in extensive alpine and arctic areas. 相似文献
Snow cover mapping is based on the geometric correction and radiometric calibration of each satellite scene before the visual bands are corrected for the terrain-effects and high solar zenith angle by using a simple radiation model. The atmospheric effect on the thermal infrared bands is corrected by using the "split-window" method. An automatic filtering routine with empirically determined thresholds is used to determine cloud-and haze-covered areas before the snow cover is computed from a linear expression using albedos of bare ground and full snow cover. By combining the satellite information with ground measurements and a digital terrain model, both the spatial distribution of snow cover and the total snow cover depletion can be obtained.
The method makes it possible to analyse the variation in regional and seasonal snow cover in wildlife habitats. The variation in snow cover depletion has been analysed in five subareas in the muskox area, and the results indicate that the snow cover pattern is an important factor which influences muskox calf crop and regional distribution of the muskox population. The method has proved useful for monitoring the duration of snow cover, and its application ought to facilitate the future study of wildlife habitats in extensive alpine and arctic areas. 相似文献
12.
Several intrusions of ultrabasic to basic composition occur in the Roslagen area of east‐central Sweden in close spatial and temporal association with the surrounding 1.90–1.87 Ga old early orogenic Svecofennian granitoids. An imprecise Sm‐Nd WR errorchron yields an age of 1895 ± 71 Ma. In spite of the penetrative deformation in the granitoids, the basic–ultrabasic rocks mostly appear undeformed and largely preserve magmatic textures with plagioclase, olivine (in some rock types), orthopyroxene and clinopyroxene, and amphibole as major constituents. The plagioclase is typically very anorthitic (ca. An90). The Roslagen intrusions range in composition from primitive to evolved (Mg# 80 to 49) but contain only 40–50 wt% SiO2. Many samples are highly elevated in Al2O3 (up to 30 wt%), CaO (up to 16 wt%) and Sr (up to 800 ppm), with strongly positive Eu and Sr anomalies, in line with being plagioclase cumulates. Although masked by cumulus effects, the relative trace element contents indicate a volcanic arc signature. The initial Nd isotope composition is homogeneously ‘mildly depleted’, with εNd of +0.3 to +1.1, and the initial Sr isotope composition ‘mildly enriched’, with εSr of +8 to +15. Non‐cumulus rocks with small Eu and Sr anomalies can be used to deduce the composition of the parental magma. This LILE‐ and LREE‐enriched and HFSE‐depleted high‐alumina basalt magma, with Mg# of ca. 50–60 and Ca# of ca. 80, most likely formed by partial melting of mantle material, enriched by fluids in a subduction environment, at 1.9 Ga. The cumulate rocks apparently crystallized from a somewhat more evolved water‐rich magma with Mg# of ca. 40. Crystallization was followed by the development of late‐magmatic to post‐magmatic coronas between olivine and plagioclase in the presence of H2O‐rich fluids. The subduction‐related setting would make these intrusions Palaeoproterozoic counterparts of Alaskan‐type ultramafic intrusions, but they differ from those in being plagioclase enriched, possibly reflecting different levels of exposure. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
13.
MATTHIAS SCHAUB KLAUS FELIX KAISER DAVID CHARLES FRANK ULF BÜNTGEN BERND KROMER SAHRA TALAMO 《Boreas: An International Journal of Quaternary Research》2008,37(1):74-86
Annually resolved tree-ring width variations and radiocarbon ages were measured from a collection of 120 Lateglacial pine stumps excavated on the Swiss Plateau. These data – representing the oldest absolutely dated wood samples worldwide – extend the absolute tree-ring chronology from Central Europe by 183 years back to 12 593 cal. yr BP (10 644 cal. yr BC). They also yield a 1420-year floating chronology covering the entire Allerød and the early Younger Dryas (14 170–12 750 cal. yr BP). Radiocarbon data suggest a 250-year jump in the 14 C reservoir correction around the time of the Allerød to Younger Dryas transition, although calendric dating of the floating chronology – by filling a ∼150 year gap – is necessary for confirmation. Various subgroups, based on the year of germination, were used to assess temporal changes in growth characteristics along the Allerød to Younger Dryas transition. Comparison of these Lateglacial data with a reference data set of living and historic pines from the Swiss Valais (AD 940–2000) revealed differences in both growth trend and level. The generally slower Lateglacial growth was likely influenced by higher geomorphic activity and severe climatic conditions. After removal of the biological age-trend, a strong common signal found in the tree-ring data suggests some skill in estimating interannual to multidecadal Lateglacial climatic variations. 相似文献
14.
Sampling of airborne pollen and spores at Ny-Alesund on Spitsbergen in the summer of 1986, by means of a Burkard pollen and spore trap, revealed only very low concentrations of air spora: a cumulative diurnal mean for the whole season of less than 200 pollen grains and just in excess of 9,000 moss and fungal spores. The most frequent pollen types recorded were those of the local taxa: Saxifraga, Salix and Oxyria digyna , whereas the share of pollen of exotic taxa, Betula, Pinus, Juniperus and Alnus , contributed only 9% of the total pollen sum. Back trajectories and pollen registrations at various aerobiological stations in Scandinavia designate central Finland as a possible source area both for the Betula and Pinus pollen. The maximum diurnal mean concentration of Cladosporium was merely 40 spores per m3 air. One may assert that the air at Ny-Alesund is almost free from allergenic pollen and spore types. 相似文献