Dinoflagellate cysts reflecting surface-water conditions in Voldafjorden, western Norway during the last 11 300 years     

KARI GR&#;SFJELD  EILIV LARSEN  HANS PETTER SEJRUP  ANNE DE VERNAL  TROND FLATEB&#;  MONICA VESTB&#;  HAFLIDI HAFLIDASON  INGE AARSETH 《Boreas: An International Journal of Quaternary Research》1999,28(3):403-415

Abundant dinocysts in a high-resolution core from Voldafjorden, western Norway, reflect changes in sea surface-water conditions during the last c. 11 300 BP. The period from c. 11 300 to 10 800 BP (Late Allerφd) was characterized by cool temperate surface-waters, high annual temperature variation and relatively strong stratification of the water column, which is characteristic of fjord environments. Due to the stratification of the surface waters, the uppermost layer may have warmed considerably. This generated a principal difference in temperature conditions between land and sea, with slightly higher temperatures in the marine environments. The period from c. 10 800 to 10 000 BP is characterized by very harsh conditions, with sea surface-water temperatures close to freezing and long lasting seasonal sea-ice cover. Similar temperature changes at the beginning and end of the Younger Dryas are characteristic for NW Europe, but those in Voldafjorden differ from those in the open sea and in the Norwegian Channel by being significantly larger. The stratification of the water column during the Late Allerφd was probably broken down because of incipient inflow of temperate normal saline waters, which caused a marked sea surface-water warming, at c. 10 000 BP. Surface-water conditions close to those of today were gradually established between c. 10000 and 9500 BP. However, these interglacial conditions were abruptly interrupted by a significant drop in winter sea surface-water temperature and salinity occurring around 9700 BP. From c. 9500 to 7000 BP the influence of temperate normal saline water masses increased stepwise until full interglacial conditions were established around c. 7000 BP. The change in the dinocyst assemblage around 7000 BP in Voldafjorden was probably related to the onset of the modern Norwegian Coastal Current, previously documented in cores from the Skagerrak and the Mid-Norwegian Continental Shelf. The last c. 7000 BP is characterized by relatively stable surface-water conditions, possibly interrupted by periods of cooling or decreased inflow of temperate normal saline water. Like several other dinoflagellate cyst records from the Norwegian-Greenland Sea, O. centrocarpum peak values are between 4000 and 5000 BP, suggesting a regional-scale oceanographic change.  相似文献   

Middle to Late Weichselian Norwegian Channel Ice Stream deposits and morphology on Jæren, southwestern Norway and the eastern North Sea area     

KNUT STALSBERG  EILIV LARSEN  DAG OTTESEN  HANS PETTER SEJRUP 《Boreas: An International Journal of Quaternary Research》2003,32(1):149-166

Glacial lineations on a bank area and a coastal lowland, both bordering the Norwegian Channel, are studied with regard to morphology and distribution by means of side-scan sonar data, detailed digital maps and fieldwork. Their genesis and age are further elucidated through stratigraphic and sedimentologic information from excavations in one typical coast-parallel drumlin. Four excavated sections revealed four lithologic units: Prodeltaic glaciomarine sand, glaciofluvial gravel, glaciomarine diamicton and deformation till. After Middle Weichselian delta progradation, glaciomarine diamicton was deposited and later subglacially reworked by a northwards flowing glacier. The two upper diamictons form the main volume of the ridge, which is interpreted as a drumlin, and imply a reinterpretation of the Jæren part of the so-called Lista moraine. Preconsolidation of glaciomarine diamicton suggests a maximum ice thickness of 500 m during drumlin formation, indicating an ice surface slope of 1 m/km. The occurrence of sediments that provided low basal shear stresses, and the orientation of drumlins and megaflutes indicating ice confluence both point to high glacier flow velocities and suggest that an ice stream, rather than a slower moving part of the ice sheet, occupied the Norwegian Channel during the Late Weichselian maximum. Deformation till overlying, more or less, undeformed glaciomarine diamicton suggests that high glacier velocities during periods of low driving stresses were possible due to a subglacial deformable layer.  相似文献   

The semi‐geostrophic Eady problem as a testbed for numerical simulations of frontogenesis     

HANS VOLKERT  CRAIG H.BISHOP 《地球，A辑:动力气象学与海洋学》1990,42(1):202-207

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The dynamics of coastal troughs and coastal fronts     

HANS ØKLAND 《地球，A辑:动力气象学与海洋学》1990,42(4):444-462

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Physical characterization of aerosol particles during nucleation events   总被引：4，自引：3，他引：4  

PASI AALTO  KAARLE HÄMERI  EDO BECKER  RODNEY WEBER  JAAN SALM  JYRKI M. MÄKELÄ  CLAUDIA HOELL  COLIN D. O'DOWD  HANS KARLSSON  HANS&#;CHRISTEN HANSSON  MINNA VÄKEVÄ  ISMO K. KOPONEN  GINTAUTAS BUZORIUS  MARKKU KULMALA 《Tellus. Series B, Chemical and physical meteorology》2001,53(4):344-358

Particle concentrations and size distributions have been measured from different heights inside and above a boreal forest during three BIOFOR campaigns (14 April–22 May 1998, 27 July–21 August 1998 and 20 March–24 April 1999) in Hyytiälä, Finland. Typically, the shape of the background distribution inside the forest exhibited 2 dominant modes: a fine or Aitken mode with a geometric number mean diameter of 44 nm and a mean concentration of 1160 cm⁻³ and an accumulation mode with mean diameter of 154 nm and a mean concentration of 830 cm⁻³. A coarse mode was also present, extending up to sizes of 20 μm having a number concentration of 1.2 cm⁻³, volume mean diameter of 2.0 μm and a geometric standard deviation of 1.9. Aerosol humidity was lower than 50% during the measurements. Particle production was observed on many days, typically occurring in the late morning. Under these periods of new particle production, a nucleation mode was observed to form at diameter of the order of 3 nm and, on most occasions, this mode was observed to grow into Aitken mode sizes over the course of a day. Total concentrations ranged from 410–45 000 cm⁻³, the highest concentrations occurring on particle production days. A clear gradient was observed between particle concentrations encountered below the forest canopy and those above, with significantly lower concentrations occurring within the canopy. Above the canopy, a slight gradient was observed between 18 m and 67 m, with at maximum 5% higher concentration observed at 67 m during the strongest concentration increases.  相似文献   

POROSITÄT UND VERDICHTUNG REZENTER, MARINER SEDIMENTE     

HANS FÜCHTBAUER  HANS-ERICH REINECK 《Sedimentology》1963,2(4):294-306

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Holocene pisoliths and encrustations associated with spring-fed surface pools, Pastos Grandes, Bolivia     

FRANÇOIS RISACHER  HANS P. EUGSTER 《Sedimentology》1979,26(2):253-270

Calcite pisoliths, with diameters ranging from 1 to 200 mm, are forming now on the surface of a playa (salar) in the Andean Altiplano (4500 m above MSL) of Bolivia. They are associated with active or recently active hot springs (20-75°C) which flow onto the playa surface. Encrustations of pieces of an older caliche-type crust, of pisoliths, of indurated mud and of older concretions are also found as well as series of small (1-3 cm high) sinter terraces (rimstone dams). Arborescent concretions and overgrowths are common and they are reminiscent of drip-stone textures. Water analyses demonstrate that calcite supersaturation (about twenty times) occurs mainly through CO₂ loss, with photosynthesis by algae and degassing the main removal mechanisms. The two available analyses indicate slight evaporation and a calcium loss between spring and pool of 2.3 mmol per litre of water. It is thought that the hot springs pick up much of their solute load from the playa sediments. The closest analogues to these deposits have been reported from caves (cave pearls and concretions). Although the depositional processes may be similar, the environment on an evaporitic playa surface is quite different. The geological implications for this newly observed pisolith environment may be considerable.  相似文献   

SUMMER TEMPERATURE VARIABILITY IN CENTRAL SCANDINAVIA DURING THE LAST 3600 YEARS     

HANS W. LINDERHOLM  BJÖRN E. GUNNARSON 《Geografiska Annaler: Series A, Physical Geography》2005,87(1):231-241

ABSTRACT. A Scots pine ( Pinus sylvestris L.) tree-ring width chronology from Jämtland, in the central Scandinavian Mountains, built from living and sub-fossil wood, covering the period 1632 BC to AD 2002, with a minor gap during AD 887–907, is presented. This is the first multi-millennial tree-ring chronology from the central parts of Fennoscandia. Pine growth in this tree line environment is mainly limited by summer temperatures, and hence the record can be viewed as a temperature proxy. Using the regional curve standardization (RCS) technique, pine-growth variability on short and long time scales was retained and subsequently summer (June–August) temperatures were reconstructed yielding information on temperature variability during the last 3600 years. Several periods with anomalously warm or cold summers were found: 450–550 BC (warm), AD 300–400 (cold), AD 900–1000 (the Medieval Warm Period, warm) and AD 1550–1900 (Little Ice Age, cold). The coldest period was encountered in the fourth century AD and the warmest period 450 to 550 BC. However, the magnitude of these anomalies is uncertain since the replication of trees in the Jämtland record is low during those periods. The twentieth century warming does not stand out as an anomalous feature in the last 3600 years. Two multi-millennial tree-ring chronologies from Swedish and Finnish Lapland, which have previously been used as summer temperature proxies, agree well with the Jämtland record, indicating that the latter is a good proxy of local, but also regional, summer temperature variability.  相似文献   

Amino acid ratios in Quaternary molluscs and foraminifera from western Norway: correlation, geochronology and paleotemperature estimates     

GIFFORD H. MILLER  HANS PETTER SEJRUP  JAN MANGERUD  BJØRN G. ANDERSEN 《Boreas: An International Journal of Quaternary Research》1983,12(2):107-124

Isoleucine epimerization (alle/Ue) ratios in the pelecypod Mya truncata and benthic foraminifer Cibicides lobalulus from emerged marine units in western Norway allow construction of a regional relative chronostratigraphy for the Ecmian and Weichselian. Two in situ interglacial sections are considered correlative by the similar biostratigraphy and alle/Ile ratios in C. lobalulus. Overlying sediments at the two sites are of both marine and glacial origin. Neither site contains a complete Weichselian record, but allelic ratios, lithostratigraphy and fauna! changes suggest at least four stadial and three interstadial events occurred along the western Norwegian coast during Early and Middle Weichselian time. Kinetic data defining the relationship between the isoleucine epimerization rate constant and temperature for the species studied allow the estimation of paleotemperatures for samples of known age. Accepting published age estimates for the Eemian interglacial beds, the average Weichselian temperature in western Norway is calculated to have been ca. 4°C below the average Holocene temperature, whereas the last interglacial was 1 to 2°C warmer that the Holocene. The limited temperature depression over this region during the Weichselian implies that coastal western Norway was ice-covered only about 30% of this period, and that Atlantic water, although not necessarily in a warm surface current as today, entered the Norwegian Sea during much of marine isotope stage 5 and intermittently during stage 3. Interpolated amino acid ages date interstadial events at ca. 94 ka, 78 ka and 52 ka, B.P., whereas glacial events are dated ca. 103 ka and bracketed by limiting dates between 78 and 89 ka, between 52 and 63 ka and less than 36 ka B.P.  相似文献   

环渤海湿地沉积物球囊霉素相关土壤蛋白分布特征及其对湿地土壤风化的影响          下载免费PDF全文

周攀  叶思源  王锦  于长斌  袁红明  裴理鑫  丁喜桂  杨娟  HANS Brix 《中国地质》2022,49(4):1075-1087

【研究目的】球囊霉素作为丛枝菌根真菌（AMF）分泌的一种难降解土壤蛋白,广泛分布于陆地生态系统中,是长期碳贮的重要组成。当前鲜有研究涉及其在滨海湿地中的分布。基于此,本文对中国环渤海主要滨海湿地表层沉积物中球囊霉素相关土壤蛋白（GRSP）的空间分布进行表征,探讨不同湿地生境下GRSP分布及其对沉积物风化的指示意义。【研究方法】本文选取辽河三角洲、北大港和黄河三角洲湿地作为研究区,对166个表层样（0~5 cm）和4个柱状样（0~35 cm）的GRSP、粒度以及常量元素进行测定,并计算化学蚀变系数（CIA）。【研究结果】研究区GRSP在空间上的动态变化受植被类型影响显著,范围在0.06~11.31 mg/g,均值为（2.35±0.16） mg/g;沉积物以粉砂质砂和砂为主,CIA值分布范围为44.79~69.59,部分区域达到中等化学风化;CIA与GRSP呈显著相关（R=~0.49,p<0.01）,总体上CIA随GRSP的增加呈现先增加后减少的趋势。【结论】GRSP在滨海湿地沉积物中的分布受到生境差异性的影响,其与CIA的相关性表征AMF及其代谢产物在地质体风化过程中发挥了潜在的生态功能。创新点：揭示了球囊霉素相关土壤蛋白与地质过程的互馈作用;阐明了丛枝菌根真菌潜在的生态功能。  相似文献