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31.
The paleoceanography in the Nordic seas was characterized by apparently repeated switching on and off of Atlantic water advection. In contrast, a continous influx of Atlantic waters probably occurred along the northern Barents Sea margin during the last 150?ka. Temporary ice-free conditions enhanced by subsurface Atlantic water advection and coastal polynyas accelerated the final ice sheet build-up during glacial times. The virtually complete dissolution of biogenic calcite during interglacial intervals was controlled mainly by CO2-rich bottom waters and oxidation of higher levels of marine organic carbon and indicates intensive Atlantic water inflow and a stable ice margin. 相似文献
32.
Félix Darve Stein Sture René de Borst Andrew J. Whittle Ian M. Smith 《国际地质力学数值与分析法杂志》2009,33(3):n\a-n\a
33.
Arctic sea ice and Eurasian climate: A review 总被引:12,自引:0,他引:12
GAO Yongqi SUN Jianqi LI Fei HE Shengping Stein SANDVEN YAN Qing ZHANG Zhongshi Katja LOHMANN Noel KEENLYSIDE Tore FUREVIK SUO Lingling 《大气科学进展》2015,32(1):92-114
The Arctic plays a fundamental role in the climate system and has shown significant climate change in recent decades,including the Arctic warming and decline of Arctic sea-ice extent and thickness. In contrast to the Arctic warming and reduction of Arctic sea ice, Europe, East Asia and North America have experienced anomalously cold conditions, with record snowfall during recent years. In this paper, we review current understanding of the sea-ice impacts on the Eurasian climate.Paleo, observational and modelling studies are covered to summarize several major themes, including: the variability of Arctic sea ice and its controls; the likely causes and apparent impacts of the Arctic sea-ice decline during the satellite era,as well as past and projected future impacts and trends; the links and feedback mechanisms between the Arctic sea ice and the Arctic Oscillation/North Atlantic Oscillation, the recent Eurasian cooling, winter atmospheric circulation, summer precipitation in East Asia, spring snowfall over Eurasia, East Asian winter monsoon, and midlatitude extreme weather; and the remote climate response(e.g., atmospheric circulation, air temperature) to changes in Arctic sea ice. We conclude with a brief summary and suggestions for future research. 相似文献
34.
We simulate the rise through the upper convection zone and emergence through the solar surface of initially uniform, untwisted,
horizontal magnetic flux, with the same entropy as the nonmagnetic plasma, that is advected into a domain 48 Mm wide by 20 Mm
deep. The magnetic field is advected upward by the diverging upflows and pulled down in the downdrafts, which produces a hierarchy
of loop-like structures of increasingly smaller scale as the surface is approached. There are significant differences between
the behavior of fields of 10 kG and 20 or 40 kG strength at 20 Mm depth. The 10 kG fields have little effect on the convective
flows and show small magnetic-buoyancy effects, reaching the surface in the typical fluid rise time from 20 Mm depth of 32
hours. 20 and 40 kG fields significantly modify the convective flows, leading to long, thin cells of ascending fluid aligned
with the magnetic field and their magnetic buoyancy makes them rise to the surface faster than the fluid rise time. The 20 kG
field produces a large-scale magnetic loop that as it emerges through the surface leads to the formation of a bipolar, pore-like
structure. 相似文献
35.
Silicon isotopes in the inner Solar System: Implications for core formation, solar nebular processes and partial melting 总被引:1,自引:0,他引:1
We report Si isotopic data on a suite of terrestrial mantle-derived samples, meteorites and a lunar sample. Our data on co-existing mantle minerals, peridotites and basalts demonstrate lack of any resolvable high temperature fractionation during igneous processes. We show that the δ30Si of the bulk silicate Earth (BSE) is identical, within analytical uncertainties, to carbonaceous and ordinary chondrites (CHUR). Based on our data the difference between δ30SiBSE and δ30SiCHUR is 0.035 ± 0.035. Whole-rock differentiated meteorites from different parent bodies (Mars, Vesta) and a lunar breccia sample also show similar δ30Si suggesting broad-scale Si isotope homogeneity in the inner Solar System with an average δ29Si = −0.20 ± 0.01 and δ30Si = −0.39 ± 0.02 relative to the NBS28 Si isotope standard.A difference between δ30SiBSE and δ30SiCHUR of 0.035, as observed in our study, translates to less than 1.67 wt.% Si in the core considering a continuous accretion model whereas estimates using a batch model are even lower. Within uncertainties (±0.035‰) in the δ30Si difference between the BSE and CHUR, a maximum of 3.84 wt.% Si could be present in the Earth’s core whereas at δ30SiBSE-δ30SiCHUR = 0, there is no requirement of Si in the Earth’s core. Such low Si in the core necessitates the presence of other light elements in the core to explain its density deficit. Our data also places constraints on the oxidation state of the Earth’s mantle during core segregation. The uncertainties in estimating the concentration of oxidized Fe in the mantle during the first 90% of accretion arise from uncertainties in the estimates of the equilibrium partition coefficient of silicon between metal and silicate at conditions relevant to core formation. For δ30SiBSE-δ30SiCHUR = 0.035 ± 0.035, the concentration of oxidized Fe in the mantle during the first 90% of accretion could be as low as ∼1%. However, at δ30SiBSE-δ30SiCHUR = 0, the Si isotope data do not require any change in the mantle concentration of oxidized Fe during accretion from the present day value of 6.26%. 相似文献
36.
Interest in integrating human connections and natural areas into resource management decision making has steadily increased. While efforts to validate place meaning dimensions have identified meanings beyond established place dependence and identity concepts, further research to identify tangible and intangible meanings of nature-based recreation areas is needed. This study sought to examine place meanings as a second-order construct consisting of ecological integrity, economic dependency, place dependence, family identity, community identity, and place identity and to determine the influence of place meanings on participatory planning intentions (PPI). Data were collected from Florida Fish and Wildlife Conservation area visitors. Confirmatory factor analysis revealed that six factors were reliable and valid, representing place meanings as an overarching concept. Structural equation modeling showed a significant association between place meanings and PPI. These findings demonstrated the importance of understanding place meanings that influence behavioral intentions, which is relevant to understanding participation in planning processes. 相似文献
37.
The results of study of six cores taken from different morphostructural zones in the Mendeleev Ridge area are discussed. Average contents of minerals of the illite group, chlorite, kaolinite, and smectite are about 60, 21, 12, and 5%, respectively. It was found that fluctuations of minerals along the section correlate with variations in sedimentation constraints in the Late Quaternary. Peaks of kaolinite usually coincide with increased contents of the sand fraction, probably, due to its delivery by icebergs. In contrast, illite shows good correlation with the pelite fraction, testifying to its transport mainly by ices and currents. Minerals of the chlorite and smectite groups in the studied cores are less informative. 相似文献
38.
M. A. Levitan K. V. Syromyatnikov I. A. Roshchina R. Stein 《Geochemistry International》2014,52(3):215-228
This paper addresses the problem of relationships between the chemical composition and color of Quaternary marine sediments using the data of X-ray fluorescence analysis for the region of the Mendeleev Rise (Arctic Ocean). The contributions of sedimentation and diagenetic factors to color formation were estimated. It was shown that lithostratigraphic correlations should be performed (with certain limitations) using only sediment layers of dark brown and pink color. 相似文献
39.
Robert Stein Dali Georgobiani Regner Trampedach Hans-Günter Ludwig Åke Nordlund 《Solar physics》2004,220(2):229-242
P-mode oscillations in the Sun and stars are excited stochastically by Reynolds stress and entropy fluctuations produced by
convection in their outer envelopes. The excitation rate of radial oscillations of stars near the main sequence from K to
F and a subgiant K IV star have been calculated from numerical simulations of their surface convection zones. P-mode excitation
increases with increasing effective temperature (until envelope convection ceases in the F stars) and also increases with
decreasing gravity. The frequency of the maximum excitation decreases with decreasing surface gravity. 相似文献
40.