Late Weichselian (Valdaian) and Holocene vegetation and environmental history of the northern Timan Ridge, European Arctic Russia     

Aage Paus  John Inge Svendsen  Alexei Matiouchkov 《Quaternary Science Reviews》2003,22(21-22):2285-2302

Lake and peat deposits from the Timan Ridge, Arctic Russia, were pollen analysed, reconstructing the vegetation history and paleoenvironment since the Last Glacial Maximum (LGM) 20–18,000 years ago. The sites studied are located inside the margins of a large paleolake of about 20 km², by us named Lake Timan. This lake developed in the Late Weichselian, more than 30,000 years after the deglaciation of this region, and was formed due to increased precipitation and warmer summers that accelerated the melting of stagnant ice within its catchment. The lake was drained during the early Holocene when the outlet rivers eroded the spillways. A new generation of much smaller lakes formed during the Holocene when the last remnants of buried glacier ice melted away causing the exposed floor of Lake Timan to subside. Since deglaciation, the following regional vegetation development has been recorded: (1) During the initial stage of Lake Timan, the dominant vegetation was discontinuous steppe/tundra, with patches of snow bed vegetation. (2) A dwarf-shrub tundra established during the Late Weichselian interstadial (Allerød), probably reflecting warmer and moister conditions. (3) The Younger Dryas cooling is recognised by a reversal to steppe/tundra and snowbeds on unstable mineral-soils, and higher palynological richness. (4) Soon after the transition into the Holocene, a birch-forest established on the Timan Ridge. (5) A cooling starting around 8200 cal.years BP initiated the deforestation of the exposed hills. In the most protected sites, birch trees persisted until later than 4000 years ago, reflecting a gradual development into the present treeless dwarf-shrub tundra.  相似文献   

Integrated modelling of population,employment and land-use change with a multiple activity-based variable grid cellular automaton     

Roger White  Inge Uljee  Guy Engelen 《International journal of geographical information science》2013,27(7):1251-1280

A constrained cellular automaton (CA) framework is used to model both land use and, at the same resolution, densities of population and economic activity. The multi-scale processes determining the location of population, economic activity and land use are captured in a variable grid CA, in which the neighbourhood of each cell includes the entire modelled area. The transition rules generating the spatial dynamics incorporate both the land use and the activities, and because they cover the entire modelled area, they represent interaction effects at all spatial scales; effectively, they are distance decay functions. In general, any particular cell hosts a number of activities (population, employment in various sectors) regardless of its land use, so in effect multiple land uses are modelled as multiple activities, although activity levels are normally highest on cells of the corresponding land use. The model is applied to both the urban-centred Greater Dublin Region and the country of Belgium, which consists of the entire polycentric urban system and its rural matrix. Results for both applications are good, as measured by the errors of both predicted populations and fractal dimensions, and the model outperforms the best existing models by these measures.  相似文献   

Life Histories, Salinity Zones, and Sublethal Contributions of Contaminants to Pelagic Fish Declines Illustrated with a Case Study of San Francisco Estuary, California, USA     

Marjorie L. Brooks  Erica Fleishman  Larry R. Brown  Peggy W. Lehman  Inge Werner  Nathaniel Scholz  Carys Mitchelmore  James R. Lovvorn  Michael L. Johnson  Daniel Schlenk  Suzanne van Drunick  James I. Drever  David M. Stoms  Alex E. Parker  Richard Dugdale 《Estuaries and Coasts》2012,35(2):603-621

Human effects on estuaries are often associated with major decreases in abundance of aquatic species. However, remediation priorities are difficult to identify when declines result from multiple stressors with interacting sublethal effects. The San Francisco Estuary offers a useful case study of the potential role of contaminants in declines of organisms because the waters of its delta chronically violate legal water quality standards; however, direct effects of contaminants on fish species are rarely observed. Lack of direct lethality in the field has prevented consensus that contaminants may be one of the major drivers of coincident but unexplained declines of fishes with differing life histories and habitats (anadromous, brackish, and freshwater). Our review of available evidence indicates that examining the effects of contaminants and other stressors on specific life stages in different seasons and salinity zones of the estuary is critical to identifying how several interacting stressors could contribute to a general syndrome of declines. Moreover, warming water temperatures of the magnitude projected by climate models increase metabolic rates of ectotherms, and can hasten elimination of some contaminants. However, for other pollutants, concurrent increases in respiratory rate or food intake result in higher doses per unit time without changes in the contaminant concentrations in the water. Food limitation and energetic costs of osmoregulating under altered salinities further limit the amount of energy available to fish; this energy must be redirected from growth and reproduction toward pollutant avoidance, enzymatic detoxification, or elimination. Because all of these processes require energy, bioenergetics methods are promising for evaluating effects of sublethal contaminants in the presence of other stressors, and for informing remediation. Predictive models that evaluate the direct and indirect effects of contaminants will be possible when data become available on energetic costs of exposure to contaminants given simultaneous exposure to non-contaminant stressors.  相似文献   

Erratum: Late glacial and holocene 10Be production rates for western Norway     

Brent M. Goehring  Øystein Strand Lohne  Jan Mangerud  John Inge Svendsen  Richard Gyllencreutz  Joerg Schaefer  Robert Finkel 《第四纪科学杂志》2012,27(5):544-544

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Ice-free conditions in Novaya Zemlya 35 000–30 000 cal years B.P., as indicated by radiocarbon ages and amino acid racemization evidence from marine molluscs     

Jan Mangerud  Darrell Kaufman  Jesper Hansen  & John Inge Svendsen 《Polar research》2008,27(2):187-208

Novaya Zemlya was covered by the eastern part of the Barents–Kara ice sheet during the glacial maximum of marine isotope stage 2 (MIS 2). We obtained ¹⁴C ages on 37 samples of mollusc shells from various sites on the islands. Most samples yielded ages in the range of 48–26 ¹⁴C Ky. Such old samples are sensitive to contamination by young ¹⁴C, and therefore their reliability was assessed using replicate analyses and amino acid geochronology. The extent of aspartic acid racemization (Asp D/L) indicates that many of the ¹⁴C ages are correct, whereas some are minimum ages only. The results indicate that a substantial part of Novaya Zemlya was ice-free about 35–27 ¹⁴C Kya, and probably even earlier. Corresponding shorelines up to >140 m a.s.l. indicate a large Barents–Kara ice sheet during early MIS 3. These results are consistent with findings from Svalbard and northern Russia: in both places a large MIS 4/3 Barents–Kara ice sheet is postulated to have retreated about 50 Kya, followed by an ice-free interstadial that lasted until up to ca. 25 Kya. The duration of the MIS 2 glaciation in Novaya Zemlya was calculated by applying the D/L values to a kinetic equation for Asp racemization. This indicates that the islands were ice covered for less than 3000 years if the basal temperature was 0^oC, and for less than 10 000 years if it was −5^oC.  相似文献   

Foreword to the special issue: Arctic Palaeoclimate and Its Extremes (APEX)     

Martin Jakobsson  Robert F. Spielhagen  Jörn Thiede  Claus Andreasen  Brenda Hall  Ólafur Ingólfsson  Kurt H. Kjær  Thijs van Kolfschoten  Gerhard Krinner  Antony Long  Juha-Pekka Lunkka  Dmitry Subetto  & John Inge Svendsen 《Polar research》2008,27(2):97-104

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Early Eocene sea floor spreading and continent-ocean boundary between Jan Mayen and Senja fracture zones in the Norwegian-Greenland Sea     

Tsikalas  Filippos  Eldholm  Olav  Faleide  Jan Inge 《Marine Geophysical Researches》2002,23(3):247-270

Sea floor spreading anomalies in the Lofoten-Greenland basins reveal an unstable plate boundary characterized by several small-offset transforms for a period of 4 m.y. after opening. North of the Jan Mayen Fracture Zone, integrated analysis of magnetic and seismic data also document a distinct, persistent magnetic anomaly associated with the continent-ocean boundary and a locally, robust anomaly along the inner boundary of the break-up lavas. These results provide improved constraints on early opening plate reconstructions, which include a new anomaly 23-to-opening pole of rotation yielding more northerly relative motion vectors than previously recognized; and a solution of the enigmatic, azimuthal difference between the conjugate Eocene parts of the Greenland-Senja Fracture Zone if the Greenland Ridge is considered a continental sliver. The results confirm high, 2.36–2.40 cm yr^–1, early opening spreading rates, and are consistent with the start of sea floor spreading during Chron 24r. The potential field data along the landward prolongations of the Bivrost Fracture Zone suggest that its location is determined by a Mesozoic transfer system which has acted as a first-order, across-margin tectono-magmatic boundary between the regional Jan Mayen and Greenland-Senja Fracture Zone systems, greatly influencing the pre-, syn- and post-breakup margin development.  相似文献   

Oberflächentemperaturen der Gesteine im hochgebirge     

Inge Dirmhirn 《Theoretical and Applied Climatology》1952,4(1):43-50

Zusammenfassung Im Sommer 1950 und 1951 wurde auf dem Sonnblick in etwa 3050 m Seehöhe die Oberflächentemperature de Gesteine thermoelektrisch gemessen. An windstillen Tagen konnten bei wolkenlosem Himmel oder geringer Bewölkung Mittagstemperaturen bis 29°C an einer 6 cm dicken, horizontalen Platte beobachtet werden, das Minimum sank nachts auf–4°C ab. Diese starken Temperaturschwankungen wurden bei hohen Windgeschwindigkeiten erheblich abgeschwächt (bis 18°C). Ein Zusammenhang der Temperaturschwankung mit der Windgeschwindigkeit konnte angegeben werden. Auf gewachsenem Fels finden sich unter sonst gleichen Verhältnissen wesentlich geringere Tagesschwankungen. Durch die starken Temperaturvariationen der Gesteine wird die mechanische Verwitterung gefördert, die ihrerseits durch Staubbildung die Albedo der gesteinsnahen Gletscherflächen herabsetzt, den Strahlungshaushalt verändert und somit die Ablation der Gletscherränder fördert.

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Summary Surface temperatures of rocks were measured thermoelectrically on the Sonnblick at an altitude of about 3050 m during the summers 1950 and 1951. On calm days with no or little cloudiness midday temperatures up to 29°C could be observed on a horizontal plate 6 cm thick. The lowest temperature at night was–4°C. Such strong temperature variations were considerably reduced by high wind velocities (to 18°C). A relation between temperature variation and wind velocity could be established. On living rock, under equal conditions, considerably smaller diurnal variations were found. The great temperature variations of the rocks further their mechanical decay which, by producing dust, reduces the albedo of the glacier surface near the rocks, thereby changing the radiation economy and furthering the ablation of the borders of the glacier.

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Résumé On a mesuré au Sonnblick (3050 m) en été 1950 et 1951 la température superficielle des roches par voie thermoélectrique. Par ciel sans nuages ou peu nuageux et temps calme, on a mesuré à midi des températures atteignant 29°C sur une pierre horizontale plate, épaisse de 6 cm.; de nuit le minimum est descendu à–4°C. Ces grands écarts de température étaient notablement réduits (jusqu'à 18°) par vent fort. On a pu donner une relation entre la variation de température et la vitesse du vent. Les variations diurnes sur roches en place sont, toutes choses égales, plus faibles. Les fortes variations de température des roches accélèrent leur désagrégation mécanique; les poussières qui en résultent diminuent l'albédo des glaciers voisins, modifient par conséquent leur bilan de rayonnement et favorisent l'ablation des marges glaciares.

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Mit 2 Textabbildungen.  相似文献   

Evidence of early deglaciation (18 000 cal a bp) and a postglacial relative sea‐level curve from southern Karmøy,south‐west Norway     

Kristian Vasskog  John‐Inge Svendsen  Jan Mangerud  Kristian Agasster Haaga  Arve Svean  Eva Maria Lunnan 《第四纪科学杂志》2019,34(6):410-423

Based on six consistent radiocarbon dates from the isolation basins Grødheimsvatnet and Kringlemyr, we estimate a minimum deglaciation age for southern Karmøy, an island in outer Boknafjorden (south‐west Norway), of around 18 000 calibrated years before present (18k cal a bp ). We use microscopic phytoplankton, macrofossils, lithostratigraphic evidence and X‐ray fluorescence data to identify the isolation contacts in the basins, and date them to 17.52–17.18k cal a bp in Grødheimsvatnet [15.57 m above present mean sea level (MSL)] and 16.19–15.80k cal a bp in Kringlemyr (11.99 m above MSL). Combining these data with previous studies, we construct a relative sea‐level (RSL) curve from 18k cal a bp until the present, which is ~3 ka longer than any previous RSL reconstruction from southern Norway. Following deglaciation, southern Karmøy has experienced a net emergence of around 16–19 m, although with significant RSL fluctuations. This includes two RSL minima well below present MSL around ~13.8 and ~10k cal a bp , and two maxima that culminated around 5–7 m above MSL during the Younger Dryas and early to mid‐Holocene, respectively. Considering eustatic sea level and modelled gravitational deformation of the geoid, we estimate a net postglacial isostatic uplift of ~120 m. © 2019 John Wiley & Sons, Ltd  相似文献   

Amino acid photostability on the Martian surface     

Inge Loes TEN KATE  James R. C. GARRY  Zan PEETERS  Richard QUINN  Bernard FOING  Pascale EHRENFREUND 《Meteoritics & planetary science》2005,40(8):1185-1193

Abstract— In the framework of international planetary exploration programs, several space missions are planned to search for organics and bio‐signatures on Mars. Previous attempts have not detected any organic compounds in the Martian regolith. It is therefore critical to investigate the processes that may affect organic molecules on and below the planet's surface. Laboratory simulations can provide useful data about the reaction pathways of organic material at Mars' surface. We have studied the stability of amino acid thin films against ultraviolet (UV) irradiation and use those data to predict the survival time of these compounds on and in the Martian regolith. We show that thin films of glycine and D‐alanine are expected to have half‐lives of 22 ± 5 hr and of 3 ± 1 hr, respectively, when irradiated with Mars‐like UV flux levels. Modelling shows that the half‐lives of the amino acids are extended to the order of 10⁷ years when embedded in regolith. These data suggest that subsurface sampling must be a key component of future missions to Mars dedicated to organic detection.  相似文献