排序方式： 共有21条查询结果，搜索用时 15 毫秒
11.
John Darwent Trine Bjørneboe Johansen 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(2):297-314
Geografisk Tidsskrift—Danish Journal of Geography 110(2):297–314, 2010 The Inglefield Land Archaeology Project undertook archaeological survey of three areas of Foulke Fjord in 2006, during which 639 archaeological features were recorded, exclusive of the large Reindeer Point Longhouse site (Darwent et al., 2008). Basedon comparisons with surveys completed in Eastern Inglefield Land (Darwent et al., 2007), the density of features in Foulke Fjord substantially exceeded those from other regions of Inglefield Land. The most parsimonious explanation for the higher occurrence of features in this region is the presence of little auk colonies on the scree slopes of the inner fjords. These birds, which roost in the millions, served as a reliable summer food source, but their feces likely provided enrichment for the local ecosystem, increasing the numbers of terrestrial and marine fauna in the region. Based on excavations at Iita (Etah) and densities of features in the fiord, Foulke Fjord appears to have been continually occupied throughout the Thule-historic period (A.D. 1250–1953), and during the previous Late Dorset period (ca. A.D. 800–1250). However, features associated with the early Paleoeskimo period (2500–500 B.C.) are located only at the outer margins of the fjord. 相似文献
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A first detailed look at the Greenland lithosphere and upper mantle, using Rayleigh wave tomography 总被引：2，自引：1，他引：2
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Lipids and trophic linkages in harp seal (Phoca groenlandica) from the eastern Barents Sea 总被引：2，自引：0，他引：2
Stig Falk-Petersen Tore Haug Kjell T. Nilssen Anette Wold Trine M. Dahl 《Polar research》2004,23(1):43-50
Fatty acid profiles and lipid biomarkers from 20 harp seals were used to investigate the foraging ecology of harp seals and the transfer of energy through the Franz Josef Land-Novaya Zemlya food chain. High levels of the Calanus fatty acid trophic markers (FATMs) 20:1(n-9) (mean 14.6%) and 22:1(n-11) (mean 6.5%), together with the typical dinoflagellate FATMs 22:6(n-3) (mean 6.5%) and C18PUFA (mean 5.5%), were found in blubber samples. Based on the analyses of the fatty acid profiles separated by principal component analysis, we confirmed the importance of polar cod ( Boreogadus saida ) and the pelagic amphipod Themisto libellula in the diet of harp seal. The high levels of 22:6(n-3), C18PUFA and C20 and C22 FATMs show that the harp seal lipids mainly originate from dinoflagellates consumed by Calanus copepods. 相似文献
14.
Paden J.D. Allen C.T. Gogineni S. Jezek K.C. Dahl-Jensen D. Larsen L.B. 《Geoscience and Remote Sensing Letters, IEEE》2005,2(2):164-168
We are developing a multifrequency multistatic synthetic aperture radar (SAR) for determining polar ice sheet basal conditions. To obtain data for designing and optimizing radar performance, we performed field measurements with a network-analyzer-based system during the 2003 field season at the North Greenland Ice Core Project camp (75.1 N and 42.3 W). From the measurements, we determine the ice sheet complex transfer function over the frequency range from 110-500 MHz by deconvolving out the system transfer function. Over this frequency range, we observe an increase in total loss of 8/spl plusmn/2.5 dB using a linear regression to the log-scale data. With the ice sheet transfer function and an ice extinction model, we estimate the return loss from the basal surface to be approximately 37 dB. These measurements have broad applicability to interpreting radar-sounding data, which are widely used in glaciological studies of the polar ice sheets. These data have also been used in the link budget for the design considerations of the multifrequency multistatic SAR system. 相似文献
15.
Mantle thermal structure and active upwelling during continental breakup in the North Atlantic 总被引：4，自引：0，他引：4
W.Steven Holbrook H.C. Larsen J. Korenaga T. Dahl-Jensen I.D. Reid P.B. Kelemen J.R. Hopper G.M. Kent D. Lizarralde S. Bernstein R.S. Detrick 《Earth and Planetary Science Letters》2001,190(3-4):251-266
Seismic reflection and refraction data acquired on four transects spanning the Southeast Greenland rifted margin and Greenland–Iceland Ridge (GIR) provide new constraints on mantle thermal structure and melting processes during continental breakup in the North Atlantic. Maximum igneous crustal thickness varies along the margin from >30 km in the near-hotspot zone (<500 km from the hotspot track) to 18 km in the distal zone (500–1100 km). Magmatic productivity on summed conjugate margins of the North Atlantic decreases through time from 1800±300 to 600±50 km3/km/Ma in the near-hotspot zone and from 700±200 to 300±50 km3/km/Ma in the distal zone. Comparison of our data with the British/Faeroe margins shows that both symmetric and asymmetric conjugate volcanic rifted margins exist. Joint consideration of crustal thickness and mean crustal seismic velocity suggests that along-margin changes in magmatism are principally controlled by variations in active upwelling rather than mantle temperature. The thermal anomaly (ΔT) at breakup was modest (100–125°C), varied little along the margin, and transient. Data along the GIR indicate that the potential temperature anomaly (125±50°C) and upwelling ratio (4 times passive) of the Iceland hotspot have remained roughly constant since 56 Ma. Our results are consistent with a plume–impact model, in which (1) a plume of radius 300 km and ΔT of 125°C impacted the margin around 61 Ma and delivered warm material to distal portions of the margin; (2) at breakup (56 Ma), the lower half of the plume head continued to feed actively upwelling mantle into the proximal portion of the margin; and (3) by 45 Ma, both the remaining plume head and the distal warm layer were exhausted, with excess magmatism thereafter largely confined to a narrow (<200 km radius) zone immediately above the Iceland plume stem. Alternatively, the warm upper mantle layer that fed excess magmatism in the distal portion of the margin may have been a pre-existing thermal anomaly unrelated to the plume. 相似文献
16.
Christian Fertner Niels Boje Groth Lise Herslund Trine Agervig Carstensen 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2015,115(2):119-132
Small towns are often considered as losing out in the current trend towards urban development. However, research from around Europe shows a great diversity of small town development, including successful development trajectories despite geographical disadvantages. Investigations into this are predominately done in the context of economic development and urban systems, but such approaches fail to explain why a number of small towns that are not centrally located near a metropolitan region are not in decay. This paper examines how the restructuring of retail and service sectors, demographic composition, residential migration, social organisation and community engagement form and affect small town (1000–5000 inhabitants) development patterns in Denmark and specific place-based endowments. The study is carried out with mixed methods, comprising a quantitative analysis of development trends, complemented by qualitative case studies in six small towns. Our findings show how favourable development paths are a combination of a positive development in population, provision of daily commodities and attractive housing, and a high number of local voluntary social organisations. Introducing the concept of ‘residential urbanism’, the paper discusses the extent to which a residentially driven urban development can compensate for the generally unfavourable regional development context. 相似文献
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Landslide and Tsunami 21 November 2000 in Paatuut,West Greenland 总被引：1，自引：0，他引：1
Dahl-Jensen Trine Larsen Lotte Melchior Pedersen Stig A. Schack Pedersen Jerrik Jepsen Hans F. Pedersen Gunver Nielsen Tove Pedersen Asger Ken Von Platen-Hallermund Frants Weng Willy 《Natural Hazards》2004,31(1):277-287
A large landslide occurred November 21, 2000 at Paatuut, facing the Vaigat Strait onthe west coast of Greenland. 90 million m3 (260 million tons) of mainly basalticmaterial slid very rapidly (average velocity 140 km/h) down from 1,000–1,400 maltitude. Approximately 30 million m3 (87 million tons) entered the sea, creatinga tsunami with an run-up height of 50 m close to the landslide and 28 m at Qullissat,an abandoned mining town opposite Paatuut across the 20 km wide Vaigat strait. Theevent was recorded seismically, allowing the duration of the slide to be estimated tocirca 80 s and also allowing an estimate of the surface-wave magnitude of the slideof 2.3. Terrain models based on stereographic photographs before and after the slidemade it possible to determine the amount of material removed, and the manner ofre-deposition. Simple calculations of the tsunami travel times are in good correspondencewith the reports from the closest populated village, Saqqaq, 40 km from Paatuut, whererefracted energy from the tsunami destroyed a number of boats. Landslides are notuncommon in the area, due to the geology with dense basaltic rocks overlying poorlyconsolidated sedimentary rocks, but the size of the Paatuut slide is unusual. Based onthe observations it is likely at least 500 years since an event with a tsunami of similarproportions occurred. The triggering of the Paatuut slide is interpreted to be caused byweather conditions in the days prior to the slide, where re-freezing melt water inpre-existing cracks could have caused failure of the steep mountain side. 相似文献
19.
Trine Marianne Holm Karin A. Koinig Tom Andersen Espen Donali Anne Hormes Dag Klaveness Roland Psenner 《Aquatic Sciences - Research Across Boundaries》2012,74(3):385-395
High Arctic lakes are among the most sensitive ecosystems and climate change strongly affects their physical properties, especially water temperature, and mixing processes. To study the effect of recent climate change on such a lake in the Arctic environment, we measured water chemistry and temperature from 2005 to 2010 in Kongressvatn, a crenogenic meromictic lake in Spitsbergen (Svalbard). In addition, we monitored water column temperatures during two consecutive years and compared them to regional air temperature data and physicochemical lake data from 1962 and 1968, two relatively cold years. Summer surface water temperature was highly correlated to air temperature, and both have increased by approximately 2°C since 1962. Temperature monitoring during 2?years showed that the warm summer of 2007 resulted in increased water temperatures even in the stratified, denser hypolimnion. Our water chemistry measurements showed that the chemocline position in 2005?C2010 was ca 12?m deeper than in 1962?C1968, and a second, weaker, chemocline appeared at metalimnetic depths of 7?C15?m. During the study period, the water level decreased by 4?m, and this change accelerated between 2008 and 2010. Our data support the hypothesis that water temperatures and stratification patterns are changing rapidly with air temperature, but changes in the catchment, such as glacial retreat and permafrost melting, may have an even stronger impact on lake properties. 相似文献
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