共查询到20条相似文献，搜索用时 31 毫秒
1.
Stein R Nam SI Schubert C Vogt C Futterer D Heinemeier J 《Science (New York, N.Y.)》1994,264(5159):692-696
Oxygen isotope records of cores from the central Arctic Ocean yield evidence for a major influx of meltwater at the beginning of the last deglaciation 15.7 thousand years ago (16,650 calendar years B.C.). The almost parallel trends of the isotope records from the Arctic Ocean, the Fram Strait, and the east Greenland continental margin suggest contemporaneous variations of the Eurasian Arctic and Greenland (Laurentide) ice sheets or increased export of low-saline waters from the Arctic within the East Greenland Current during the last deglaciation. On the basis of isotope and carbon data, the modern surface- and deep-water characteristics and seasonally open-ice conditions with increased surface-water productivity were established in the central Arctic at the end of Termination lb about 7.2 thousand years ago or 6,000 calendar years B.C.). 相似文献
2.
Spielhagen RF Werner K Sørensen SA Zamelczyk K Kandiano E Budeus G Husum K Marchitto TM Hald M 《Science (New York, N.Y.)》2011,331(6016):450-453
The Arctic is responding more rapidly to global warming than most other areas on our planet. Northward-flowing Atlantic Water is the major means of heat advection toward the Arctic and strongly affects the sea ice distribution. Records of its natural variability are critical for the understanding of feedback mechanisms and the future of the Arctic climate system, but continuous historical records reach back only ~150 years. Here, we present a multidecadal-scale record of ocean temperature variations during the past 2000 years, derived from marine sediments off Western Svalbard (79°N). We find that early-21st-century temperatures of Atlantic Water entering the Arctic Ocean are unprecedented over the past 2000 years and are presumably linked to the Arctic amplification of global warming. 相似文献
3.
Herman Y 《Science (New York, N.Y.)》1970,169(3944):474-477
Sediment cores from the Arctic Ocean yield significant faunal and lithologic evidence of alternating cold and milder periods for the last 6 million years. Although high-latitude continental glaciation commenced prior to 6 million years ago, the Arctic Ocean remained free of permanent pack ice up to approximately 0.7 million years ago, after which successive ice-covered and ice-free conditions existed. 相似文献
4.
The derivation of a marine gravity field from satellite altimetry over permanently ice-covered regions of the Arctic Ocean provides much new geophysical information about the structure and development of the Arctic sea floor. The Arctic Ocean, because of its remote location and perpetual ice cover, remains from a tectonic point of view the most poorly understood ocean basin on Earth. A gravity field has been derived with data from the ERS-1 radar altimeter, including permanently ice-covered regions. The gravity field described here clearly delineates sections of the Arctic Basin margin along with the tips of the Lomonosov and Arctic mid-ocean ridges. Several important tectonic features of the Amerasia Basin are clearly expressed in this gravity field. These include the Mendeleev Ridge; the Northwind Ridge; details of the Chukchi Borderland; and a north-south trending, linear feature in the middle of the Canada Basin that apparently represents an extinct spreading center that "died" in the Mesozoic. Some tectonic models of the Canada Basin have proposed such a failed spreading center, but its actual existence and location were heretofore unknown. 相似文献
5.
The chlorofluoromethanes (CFMs: CCl(2)F(2) and CCl(3)F), methyl chloroform (CH(3)CCl(3)), and carbon tetrachloride (CCl(4)) have been measured in deep waters of the Arctic Ocean. Oceanic and atmospheric inventories of these compounds result from known anthropogenic releases; because the CFMs and CCl(4) are also chemically nonreactive, they can be used as transient tracers of ocean circulation. The input history of CCl(4) is longer than that of any other transient tracer identified to date( approximately 70 years). This long input history, together with an e-folding time scale of increase(tau) of approximately 28 years, makes CCl(4) potentially the most useful tracer for calibrating models of the oceanic uptake of the fossil-fuel CO(2) transient(tau approximately 25 years). The bottom water of the Nansen Basin, Arctic Ocean, has detectable CCl(4) but undetectable CFM(s) and CH(3)CCl(3), which suggests either that the bottom water is approximately 50 years old, or that there is a small, nonanthropogenic component of atmospheric CCl(4)(<6 parts per trillion by volume). 相似文献
6.
Dynamics of recent climate change in the Arctic 总被引：2，自引：0，他引：2
The pattern of recent surface warming observed in the Arctic exhibits both polar amplification and a strong relation with trends in the Arctic Oscillation mode of atmospheric circulation. Paleoclimate analyses indicate that Arctic surface temperatures were higher during the 20th century than during the preceding few centuries and that polar amplification is a common feature of the past. Paleoclimate evidence for Holocene variations in the Arctic Oscillation is mixed. Current understanding of physical mechanisms controlling atmospheric dynamics suggests that anthropogenic influences could have forced the recent trend in the Arctic Oscillation, but simulations with global climate models do not agree. In most simulations, the trend in the Arctic Oscillation is much weaker than observed. In addition, the simulated warming tends to be largest in autumn over the Arctic Ocean, whereas observed warming appears to be largest in winter and spring over the continents. 相似文献
7.
Broecker WS 《Science (New York, N.Y.)》1975,188(4193):1116-1118
Two arguments are presented, one in favor of the existence of thicker ice in the Arctic Ocean during glacial time, and the other in favor of a full-fledged Arctic ice cap. The first is based on the Greenland air temperature record obtained from isotopic studies of the Camp Century ice core. The second is based on the oxygen isotope record of benthic foraminifera from a deep Pacific Ocean core. 相似文献
8.
A Late Cretaceous (probably Maestrichtian) silicoflagellate assemblage has been recovered for the first time from the middle section of a core taken from the Alpha Cordillera in the central Arctic Ocean. The finding of Globigerina pachyderma in the top and very rarely in the bottom part of the core suggests a faulting or slumping process in the area. 相似文献
9.
Human-induced Arctic moistening 总被引：1，自引：0，他引：1
The Arctic and northern subpolar regions are critical for climate change. Ice-albedo feedback amplifies warming in the Arctic, and fluctuations of regional fresh water inflow to the Arctic Ocean modulate the deep ocean circulation and thus exert a strong global influence. By comparing observations to simulations from 22 coupled climate models, we find influence from anthropogenic greenhouse gases and sulfate aerosols in the space-time pattern of precipitation change over high-latitude land areas north of 55 degrees N during the second half of the 20th century. The human-induced Arctic moistening is consistent with observed increases in Arctic river discharge and freshening of Arctic water masses. This result provides new evidence that human activity has contributed to Arctic hydrological change. 相似文献
10.
A computer model of coupled ice sheet-ice shelf behavior was used to evaluate whether observed changes in atmospheric CO(2) concentration could have caused the advance and retreat of Pleistocene ice sheets in the Eurasian Arctic. For CO(2) concentrations below a threshold of approximately 250 parts per million, an extensive marine-based ice sheet covering Scandinavia, the Barents, Kara, and East Siberian seas, and parts of the Arctic Ocean developed in the model simulations. In the simulations, climatic warming associated with the Holocene rise of atmospheric CO(2) was sufficient to collapse this widespread glaciation and restore present-day ice conditions. 相似文献
11.
Contaminant lead in sediments underlying boundary currents in the Arctic Ocean provides an image of current organization and stability during the past 50 years. The sediment distributions of lead, stable lead isotope ratios, and lead-210 in the major Arctic Ocean basins reveal close coupling of the Eurasian Basin with the North Atlantic during the 20th century. They indicate that the Atlantic water boundary current in the Eurasian Basin has been a prominent pathway, that contaminant lead from the Laptev Sea supplies surface water in the transpolar drift, and that the Canadian and Eurasian basins have been historically decoupled. 相似文献
12.
An empirical model of carbon flux and (14)C-derived ages of the water in the Canada Basin of the Arctic Ocean as a function of depth was used to estimate the long-term rate of primary production within this region. An estimate can be made because the deep waters of the Canadian Basin are isolated from the world oceans by the Lomonosov Ridge (sill depth about 1500 meters). Below the sill, the age of the water correlates with increased nutrients and oxygen utilization and thus provides a way to model the average flux of organic material into the deep basin over a long time period. The (14)C ages of the deep water in the Canada Basin were about 1000 years, the carbon flux across the 1500-meter isobath was 0.3 gram of carbon per square meter per year, and the total production was 9 to 14 grams of carbon per square meter per year. Such estimates provide a baseline for understanding the role of the Arctic Ocean in global carbon cycling. 相似文献
13.
Flight directions of birds migrating at high geographic and magnetic latitudes can be used to test bird orientation by celestial or geomagnetic compass systems under polar conditions. Migration patterns of arctic shorebirds, revealed by tracking radar studies during an icebreaker expedition along the Northwest Passage in 1999, support predicted sun compass trajectories but cannot be reconciled with orientation along either geographic or magnetic loxodromes (rhumb lines). Sun compass routes are similar to orthodromes (great circle routes) at high latitudes, showing changing geographic courses as the birds traverse longitudes and their internal clock gets out of phase with local time. These routes bring the shorebirds from high arctic Canada to the east coast of North America, from which they make transoceanic flights to South America. The observations are also consistent with a migration link between Siberia and the Beaufort Sea region by way of sun compass routes across the Arctic Ocean. 相似文献
14.
The Arctic Research and Policy Act of 1984 was designed to advance arctic research in the national interest. Some of the research fields that require attention are weather and climate; national defense; renewable and nonrenewable resources; transportation; communications and spacedisturbance effects; environmental protection; health, culture, and socioeconomics; and international cooperation. A research framework recommended by the Arctic Research Commission includes, in order of priority, integrated investigations to understand: (i) the Arctic Ocean (including the marginal seas, sea ice, and seabed) and how the ocean and atmosphere operate as coupled components of the arctic system; (ii) the coupled atmosphere and land components and how their interaction governs the terrestrial environment; and (iii) the high-latitude upper atmosphere and its extension into the magnetosphere with emphasis on predicting and mitigating effects on communications and defense systems. A separate recommendation is for high priority research to resolve the major health, behavioral, and cultural problems related to the arctic environment. Recommendations are also made concerning support services and management. 相似文献
15.
The largest flux of terrigenous organic carbon into the ocean occurs in dissolved form by way of rivers. The fate of this material is enigmatic; there are numerous reports of conservative behavior over continental shelves, but the only knowledge we have about removal is that it occurs on long unknown time scales in the deep ocean. To investigate the removal process, we evaluated terrigenous dissolved organic carbon concentration gradients in the Beaufort Gyre of the western Arctic Ocean, which allowed us to observe the carbon's slow degradation. Using isotopic tracers of water-mass age, we determined that terrigenous dissolved organic carbon is mineralized with a half-life of 7.1 +/- 3.0 years, thus allowing only 21 to 32% of it to be exported to the North Atlantic Ocean. 相似文献
16.
Buckley JR Gammelsrød T Johannessen JA Johannessen OM Røed LP 《Science (New York, N.Y.)》1979,203(4376):165-167
Observations taken on an expedition into the Arctic Ocean north of Spitsbergen indicated the existence of a region of wind-driven upwelling along the edge of the ice pack. Models underestimate the 12-kilometer width of the upwelling region. 相似文献
17.
北冰洋是世界上最小、最浅和最冷的大洋,位于地球最北端,终年覆盖着海冰,是地球的最大冷源之一。北冰洋的海冰变化在不同的时间尺度上影响着全球的气候变化。卫星遥感技术是海冰监测的有效手段之一。目前为止,国内外相关海冰研究机构已获取了三十多年的海冰数据,这些数据是今后更加深入地开展北冰洋海冰研究的重要依据。针对海量的海冰卫星遥感数据,在Flex Viewer开源框架下,利用互联网应用(rich internet applications,RIA)技术和Web GIS技术,开发了北冰洋海冰卫星遥感信息系统。系统具有GIS功能强大、界面友好、平台无关以及开发效率高、开发成本低等优点,为北冰洋海冰遥感数据采集、查询、空间分析和实时数据服务的网络应用提供了一种很好的解决方案。 相似文献
18.
Murcray WB 《Science (New York, N.Y.)》1963,141(3583):802-804
The emission spectrum of the atmosphere over the Arctic Ocean was observed during a period when atmosphere and snow surface temperatures were about -40 degrees C. The main contributions to the emission in the 5-to 21-micron range came from ozone and carbon dioxide, with water vapor playing a minor part. 相似文献
19.
Massive phytoplankton blooms under Arctic sea ice 总被引：3，自引：0，他引：3
Arrigo KR Perovich DK Pickart RS Brown ZW van Dijken GL Lowry KE Mills MM Palmer MA Balch WM Bahr F Bates NR Benitez-Nelson C Bowler B Brownlee E Ehn JK Frey KE Garley R Laney SR Lubelczyk L Mathis J Matsuoka A Mitchell BG Moore GW Ortega-Retuerta E Pal S Polashenski CM Reynolds RA Schieber B Sosik HM Stephens M Swift JH 《Science (New York, N.Y.)》2012,336(6087):1408
Phytoplankton blooms over Arctic Ocean continental shelves are thought to be restricted to waters free of sea ice. Here, we document a massive phytoplankton bloom beneath fully consolidated pack ice far from the ice edge in the Chukchi Sea, where light transmission has increased in recent decades because of thinning ice cover and proliferation of melt ponds. The bloom was characterized by high diatom biomass and rates of growth and primary production. Evidence suggests that under-ice phytoplankton blooms may be more widespread over nutrient-rich Arctic continental shelves and that satellite-based estimates of annual primary production in these waters may be underestimated by up to 10-fold. 相似文献
20.
Tritium measurements in the Arctic Ocean confirm a marked near-surface stratification. Sea water at 400 meters' depth, however, is less than 3 years old, suggesting a contribution to this water mass due to sinking along the continental shelf. The top ice layer on the Ward Hunt Island ice field is older than 25 years. 相似文献