Øvre Æråsvatn - palynostratigraphy of a 22,000 to 10,000 BP lacustrine record on Andøya, northern Norway     

TORBJØRN ALM 《Boreas: An International Journal of Quaternary Research》1993,22(3):171-188

Radiocarbon datings of a 4.10 m long lacustrine sequence from Lake Øvre Æråsvatn reveal continuous sediment accumulation during most of the Late Weichselian. starting before 21.800 ± 410 BP. The pollen record for the period 21,800 to 12,800 RP is uniform and is strongly dominated by Poaceae. Pollen influx variations suggest a succession of climatic ameliorations and deteriorations. Low to Middle Arctic. interstadial conditions prevailed from 21.000 to 19.650 (19.000) BP. A pronounced climatic deterioration followed. culminating at c. 18,85018,500 BP. synchronous with a glacial advance over the nearby Endletvatn and Nedre Æråsvatn basins At c 18.300 BP. a climatic amelioration triggered important changes in the lacustrine environment. Organogenic gyttja (2.56 m) accumulated from 18,300 to 15,000 BP. indicating a eutrophic lacustrine environment. Sparsity of minerogenic material suggests an arid climate with low surface runoff. Further ameliorations occurred from c. 17,400 to 16,800 BP and 16,000 to 15,000 BP. From c. 15.000 BP onwards. a climatic deterioration is indicated. The 17,800 to 10,500 BP record is fragmentary. At c. 10,500 BP. an improving climate induced establishment of Betula nana –Empetrum heaths. rapidly succeeded by mesic Betula pubescens Filipendula woodlands.  相似文献   

A case study of strong winds at an Arctic front     

SIGBJØRN GRØNAS  PAUL SKEIE 《地球，A辑:动力气象学与海洋学》1999,51(5):865-879

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THE ROLE OF ATMOSPHERIC CIRCULATION PATTERNS IN AGROCLIMATE VARIABILITY IN FINLAND, 1961–2011          下载免费PDF全文

MASOUD IRANNEZHAD  DELIANG CHEN  BJØRN KLØVE 《Geografiska Annaler: Series A, Physical Geography》2016,98(4):287-301

This study evaluates interannual variations and trends in growing season daily temperature sum and daily precipitation sum in Finland during 1961–2011, and their connections to well known atmospheric circulation patterns. Changes in summer (June–August) climate partially explain changes in growing season daily temperature sum and daily precipitation sum over Finland, which naturally decreased from south to north. On a national scale, growing season warmed and became wetter during 1961–2011, as growing season daily temperature sum and daily precipitation sum significantly (p < 0.05) increased by 5.01 ± 3.17°C year^–1 and 1.39 ± 0.91 mm year^–1, respectively. The East Atlantic pattern was the most influential atmospheric circulation pattern for variations in growing season daily temperature sum (rho = 0.40) across Finland and the East Atlantic/West Russia pattern was most influential for growing season daily precipitation sum variability (rho = –0.54). There were significant (p < 0.05) increasing trends in growing season daily temperature sum and daily precipitation sum throughout Finland during 1961–2011. Increased growing season daily temperature sum was mainly observed in northern, central, western, eastern and coastal areas of south‐western Finland. This warming was positively associated with the East Atlantic pattern in the north, centre and south, but negatively associated with the East Atlantic/West Russia pattern in eastern Finland. Increased GSP mostly occurred in southern, eastern, western, central, northern and north‐western Finland. These wetting trends were positively correlated with the East Atlantic pattern in the north and negatively correlated with the Polar pattern in the south and the East Atlantic/West Russia pattern in the east, west, centre and north‐east of Finland. The overall agroclimatic year‐to‐year variability in Finland between 1961 and 2011 was mostly linked to variations in the East Atlantic and East Atlantic/West Russia patterns.  相似文献   

Observations of dawn–dusk aligned polar cap aurora during the substorms of January 21, 2005     

A.M. Du  W. Sun  B.T. Tsurutani  R.N. Boroyev  A.V. Moiseyev 《Planetary and Space Science》2011,59(13):1551-1558

A new type of polar cap aurora, dawn–dusk aligned polar cap aurora (DDAPCA), was detected during the exceptionally intense January 21, 2005 substorm (AE_max=3504 nT). The DDAPCA was located at very high latitude (>85° MLAT) in the polar cap region. As the interplanetary magnetic field (IMF) GSM By component rotated from a positive to a negative value, the DDAPCA tilt angle relative to the dawn–dusk direction rotated anticlockwise and reached ∼45°. It is speculated that the DDAPCA arises from the formation of an X-line in the distant (>80R_E) tail due to polar cap magnetic field reconnection under unusually high solar wind compression conditions.  相似文献   

Deglaciation of the southeastern Norwegian Sea towards the end of the last glacial age     

KJELL R. BJØRKLUND  JØRN THIEDE  HANS HOLTEDAHL 《Boreas: An International Journal of Quaternary Research》1979,8(2):133-135

In a region of generally thin Holocene sediment cover along the outer Norwegian continental margin, a 565 cm long piston core was taken, which contained more than 4 m of Holocene clayey silty sediments. A several decimetres thick sandy horizon separated the glacial marine clays with ice-dropped components and the fine-grained Holocene sediments which have bulk sedimentation rates of more than 40 cm/1000 years. The scarcity of biogenous sediment components in the glacial sediments and the increasing frequency of benthonic as well as planktonic fossils in the Holocene deposits points to important changes in the Norwegian Sea hydrography during the time of the Scandinavian deglaciation.  相似文献   

The ¹⁴C age of the Toten' mammoth, eastern Norway     

BJØRN A. FOLLESTAD  INGRID U. OLSSON 《Boreas: An International Journal of Quaternary Research》1979,8(3):307-312

A mammoth tusk find from Toten in Oppland, eastern Norway, has been re-dated by the EDTA method. On examining the tusk for heavy metals, the porous parts were found to have the highest concentration. This fact, together with earlier experience from selecting bone samples for ¹⁴C dating, favour the choice of the hard non-porous parts. The influence of possible minor contaminants remaining after pretreatment is discussed. Because of high cosmic-ray intensity the background deviated from the normal stable value. The variations were studied carefully. The final result is that the net activity of the bone is so close to zero that it is questionable whether the age is 'finite'. It is concluded that the tusk is older than 28,000 years.  相似文献   

The stilt-legged deer Sangamona of the North-American Pleistocene     

BJÖRN KURTÉN 《Boreas: An International Journal of Quaternary Research》1979,8(3):313-321

Material of the cervid Sangamona fugitiva Hay 1920, including a partial skeleton from Frankstown Cave, Pennsylvania, is described. The species is known from Wisconsinan deposits in the central and eastern United States, with a terminal date of about 9440 B.P. It is a stilt-legged form differing widely from its contemporary in the West, Navahoceros , in which the limbs are short and plump.  相似文献   

The Middle Weichselian - Late Weichselian boundary: Comments and suggestions     

BJØRN G. ANDERSEN 《Boreas: An International Journal of Quaternary Research》1979,8(3):397-398

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The last deglaciation (20,000 to 11,000 B. P.) on Andoya, northern Norway     

TORE O. VORREN  KARL-DAG VORREN  TORBJØRN ALM  STEINAR GULLIKSEN  REIDAR LØVLIE 《Boreas: An International Journal of Quaternary Research》1988,17(1):41-77

Cores representing a 5.5m long sequence recovered from lake Æråsvatnet have been investigated for lithostratigraphy, micro- and macrofossils and radiocarbon chronology. For the first time in Fennoscandia the maximum Weichselian advance has been closely bracketed with radiocarbon datings (19,000–18,500 B.P.). A continuous stratigraphy from 18,500 B.P. and onwards, partly marine and partly lacustrine, discloses the local shoreline displacement, the palaeovegetation, the palaeoclimate and, together with other data, the deglaciation history. Two phases with a prevailing High Arctic climate have occurred: 18,000 to 16,000 B.P. and 13,700 to 12,800 B.P. Important climatic amelioration accelerating the deglacial recession occurred 16,000, 12,800 and 12,000 B.P. The continental ice sheet was situated close to its maximum position until about 16,000 B.P. The following deglaciation was interrupted by (a minor ?) readvance/halt about 15,000 B.P. (the Flesen event), 13,700-13,000 B.P. (the D-event), 12,500 B.P. (the Skarpnes event) and 11,000–10,000 B.P. (the TromsØ-Lyngen event). The deglaciation chronology and pattern can be correlated with the suggested deep-sea-stratigraphy-based stepwise pattern relying on the old age alternative for termination IA.  相似文献   

Radiocarbon-dated mammoth (Mammuthus primigenius Blumenbach) finds in South Sweden     

BJÖRN E. BERGLUND  SÖREN HAKANSSON  ERIK LAGERLUND 《Boreas: An International Journal of Quaternary Research》1976,5(3):177-191

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