Differential response at the seafloor during Palaeocene and Eocene ocean warming events at Walvis Ridge,Atlantic Ocean (ODP Site 1262)          下载免费PDF全文

Arne Deprez  Sofie Jehle  André Bornemann  Robert P. Speijer 《地学学报》2017,29(1):71-76

The Latest Danian Event (LDE, c. 62.1 Ma) is an early Palaeogene hyperthermal or transient (<200 ka) ocean warming event. We present the first deep‐sea benthic foraminiferal faunal record to study deep‐sea biotic changes together with new benthic (Nuttallides truempyi) stable isotope data from Walvis Ridge Site 1262 (Atlantic Ocean) to evaluate whether the LDE was controlled by similar processes as the minor early Eocene hyperthermals. The spacing of the double negative δ¹³C and δ¹⁸O excursion and the slope of the δ¹⁸O–δ¹³C regression are comparable, strongly suggesting a similar orbital control and pacing of eccentricity maxima as well as a rather homogeneous carbon pool. However, in contrast to early Eocene hyperthermals, the LDE exhibits a remarkable stability of the benthic foraminiferal fauna. This lack of benthic response could be related to the absence of threshold‐related circulation changes or better pre‐adaptation to elevated deep‐sea temperatures, as the LDE was superimposed on a cooling trend, in contrast to early Eocene warming.  相似文献   

Zircon fission‐track ages from Newfoundland—A proxy for high geothermal gradients and exhumation before opening of the Central Atlantic Ocean     

Arne P. Willner  Stuart N. Thomson  Johannes Glodny  Hans‐Joachim Massonne  Rolf L. Romer  Cees R. van Staal  Alexandre Zagorevski 《地学学报》2019,31(1):1-10

Following Appalachian orogenesis, metamorphic rocks in central Newfoundland were exhumed and reburied under Tournaisian strata. New zircon fission‐track (ZFT) ages of metamorphic rocks below the Tournaisian unconformity yield post‐depositionally reset ages of 212–235 Ma indicating regional fluid‐absent reheating to at least ≥220°C. Post‐Tournaisian sedimentary thicknesses in surrounding basins show that burial alone cannot explain such temperatures, thus requiring that palaeo‐geothermal gradients increased to ≥30–40°C/km before final late Triassic accelerated cooling. We attribute these elevated palaeo‐geothermal gradients to localized thermal blanketing by insulating sediments overlying radiogenic high‐heat‐producing granitoids. Late Triassic rifting and magmatism before break up of Pangaea likely also contributed to elevated heat flow, as well as uplift, triggering late Triassic accelerated cooling and exhumation. Thermochronological ages of 240–200 Ma are seen throughout Atlantic Canada, and record rifting and basaltic magmatism on the conjugate margins of the Central Atlantic Ocean preceding the onset of oceanic spreading at ~190 Ma.  相似文献   

Modern modes of provenance and dispersal of terrigenous sediments in the North Pacific and Bering Sea: implications and perspectives for palaeoenvironmental reconstructions   总被引：1，自引：0，他引：1  

Rong Wang  Boris K. Biskaborn  Arne Ramisch  Jian Ren  Yongzhan Zhang  Rainer Gersonde  Bernhard Diekmann 《Geo-Marine Letters》2016,36(4):259-270

During expedition 202 aboard the RV Sonne in 2009, 39 seafloor surface sediment sites were sampled over a wide sector of the North Pacific and adjoining Bering Sea. The data served to infer land–ocean linkages of terrigenous sediment supply in terms of major sources and modes of sediment transport within an over-regional context. This is based on an integrated approach dealing with grain-size analysis, bulk mineralogy and clay mineralogy in combination with statistical data evaluation (end-member modelling of grain-size data, fuzzy cluster analysis of mineralogical data). The findings on clay mineralogy served to update those of earlier work extracted from the literature. Today, two processes of terrigenous sediment supply prevail in the study area: far-distance aeolian sediment supply to the pelagic North Pacific, and hemipelagic sediment dispersal from nearby land sources via ocean currents along the continental margins and island arcs. Aeolian particles show the finest grain sizes (clay and fine silt), whereas hemipelagic sediments have high abundances of coarse silt. Exposed sites on seamounts and the continental slope are partly swept by strong currents, leading to residual enrichment of fine sand. Four sediment sources can be distinguished on the basis of distinct index minerals revealed by statistical data analysis: dust plumes from central Asia (quartz, illite), altered materials from the volcanic regions of Kamchatka and the Aleutian Arc (smectite), detritus from the Alaskan Cordillera (chlorite, hornblende), and fluvial detritus from far-eastern Siberia and the Alaska mainland (quartz, feldspar, illite). These findings confirm those of former studies but considerably expand the geographic range of this suite of proxies as far south as 39°N in the open North Pacific. The present integrated methodological approach proved useful in identifying the major modern processes of terrigenous sediment supply to the study region. This aspect deserves attention in the selection of sediment core sites for future palaeoenvironmental reconstructions related to aeolian and glacial dynamics, as well as the recognition of palaeo-ocean circulation patterns in general.  相似文献   

The significance of “diagenetic crystallization rhythmites” at the Nanisivik Pb-Zn-Ag deposit,Baffin Island,Canada     

D. C. Arne  S. A. Kissin 《Mineralium Deposita》1989,24(3):230-232

Conclusions Rhythmically banded ore textures at the Nanisivik Pb-Zn-Ag deposit are identical to those commonly referred to as diagenetic crystallization rhythmites or DCRs. The presence of such textures in a demonstrably epigenetic orebody indicates that their formation is not necessarily indicative of early diagenetic sulfide mineralization. Although the development of such textures may occur in near-surface and/or early diagenetic environments, their presence alone is not a compelling constraint on the timing of ore formation.  相似文献   

Interpretation of Mauna Loa atmospheric transmission relative to aerosols,using photometric precipitable water amouts     

Ellsworth G. Dutton  John J. Deluisi  P. Arne 《Journal of Atmospheric Chemistry》1985,3(1):53-68

Precipitable water measurements made coincident in time and space with direct broadband solar irradiance measurements are used in conjunction with an atmospheric transmission model to derive a parameter whose major dependence is on total aerosol extinction. Irradiance measurements are used to calculate an atmospheric transmission factor (ATF) that is independent of the instrument calibration and the extraterrestrial solar constant. The dependency of the ATF on precipitable water is determined using LOWTRAN5, an atmospheric transmission model with high spectral resolution. Precipitable water measurements are then used to adjust the measured ATF to correspond to an ATF value obtained for a constant precipitable water amount. The remaining variability in the adjusted ATF is due mostly to aerosol extinction. The technique is applied to a 6-year period (1978–1983) for clear-sky mornings at Mauna Loa, Hawaii (MLO). MLO ATF aerosol residuals are compared with independently measured monochromatic aerosol optical depth. Results show that the ATF aerosol residual is nearly equal to the 500 nm aerosol optical depth prior to the eruption of E1 Chichon, at which time a nonlinear time-dependent relationship between the two quantities is evident. ATF aerosol residuals reflect the spectrally integrated aerosol influence on transmission and, therefore, could indicate better than monochromatic optical depth the radiation balance perturbations due to aerosols. The 6-year precipitable water record for MLO, determined from a dual-channel sunphotometer, has a mean value of 0.3 cm. An annual cycle in precipitable water is evident, as is a 4-month 5-standard-deviation drought from December 1982 through March 1983.  相似文献   

利用多波段分光仪观测生物有效UV辐射、臭氧总量和云的影响     

Arne Dahlback  除多 《气象科技》2001,29(3):58-62

该文介绍了一种利用紫外分光仪进行辐照度观测获取生物有效UV辐射、臭氧总量和云的光学厚度的方法。这些量是观测的辐照度与辐射传输计算相结合后测定的。该方法被用于具有 4个中心波长为 30 5、32 0、340和 380nm ,宽度为 10nm的 4波段分光仪。将这种仪器与高精度分光光度计在美国圣迭戈不同天气条件下进行了为期 1周的对比观测。当太阳天顶角 (SZA) <80°时 ,CIE 权重UV辐射剂量率的相对误差为 1.4± 3.2 %。晴天条件下 ,当SZA <80°时 ,相对误差为 0 .6± 1.5%。该仪器观测的辐照度推算的臭氧总量对云并不敏感。这种仪器还与Dobson和Brewer仪器在挪威奥斯陆进行了一年多的对比观测。整个观测期间 (包括有云的情况 )获得的臭氧总量相对误差为 0 .3± 2 .9%。当晴天和SZA <6 0°时 ,标准差减小到 1.9%。将仪器观测中所获得的臭氧总量和云的光学厚度输入到辐射传输模式 ,可以计算从 2 90～ 4 0 0nm分辨率为 1nm的整个光谱。这样计算的光谱与同时用高精度分光光度计观测的光谱在晴天及有云的条件下非常一致 ,所以 ,这种光谱可以用于测定任何作用光谱的辐射剂量率。而计算这种光谱只需要一个UV B通道和一个UV A通道  相似文献   

Future ocean uptake of CO2: interaction between ocean circulation and biology   总被引：1，自引：0，他引：1  

Ernst Maier-Reimer  Uwe Mikolajewicz  Arne Winguth 《Climate Dynamics》1996,12(10):711-722

We discuss the potential variations of the biological pump that can be expected from a change in the oceanic circulation in the ongoing global warming. The biogeochemical model is based on the assumption of a perfect stoichiometric composition (Redfield ratios) of organic material. Upwelling nutrients are transformed into organic particles that sink to the deep ocean according to observed profiles. The physical circulation model is driven by the warming pattern as derived from scenario computations of a fully coupled ocean-atmosphere model. The amplitude of the warming is determined from the varying concentration of atmospheric CO₂. The model predicts a pronounced weakening of the thermohaline overturning. This is connected with a reduction of the transient uptake capacity of the ocean. It yields also a more effective removal of organic material from the surface which partly compensates the physical effects of solubility. Both effects are rather marginal for the evolution of atmospheric pCO₂. Running climate models and carbon cycle models separately seems to be justified. Received: 9 August 1995 / Accepted: 22 April 1996  相似文献   

Boundary-layer ozone depletion as seen in the Norwegian Arctic in spring     

Sverre Solberg  Norbert Schmidbauer  Arne Semb  Frode Stordal  Øystein Hov 《Journal of Atmospheric Chemistry》1996,23(3):301-332

Several years of measurements of ozone, hydrocarbons, sulphate and meteorological parameters from Spitsbergen in the Norwegian Arctic are presented. Most of the measurements were taken on the Zeppelin Mountain at an altitude of 474 m a.s.l. The focus is the episodes of ozone depletion in the lower troposphere in spring, which are studied in a climatological way. Episodes of very low ozone concentrations are a common feature on the Zeppelin Mountain in spring. The low ozone episodes were observed from late March to the beginning of June. When the effect of transport direction was subtracted, the frequenty of the low ozone episodes was found to peak in the beginning of May, possibly reflecting the seasonal cycle in the actual depletion process. Analyses based on trajectory calculations show that most of the episodes occurred when the air masses were transported from W-N. Ozone soundings show that the ozone depletion may extend from the surface and up to 3–4 km altitude. The episodes were associated with a cold boundary layer beneath a thermally stable layer, suppressing mixing with the free troposphere. The concentration of several individual hydrocarbons was much lower during episodes of low ozone than for the average conditions. The change in concentration ratio between the hydrocarbons was in qualitative agreement with oxidation of hydrocarbons by Br and Cl atoms rather than by OH radicals.  相似文献   

‘Trapped sea-water’ in Rørholtfjorden     

Arne Lande 《Aquatic Sciences - Research Across Boundaries》1972,34(1):34-40

Summary Trapped sea-water in R?rholtfjorden, Telemark, Norway, was discovered in 1951 by?smund Ystad who was a student at the Department of Limnology, University of Oslo. The lake was investigated continuously from August 1951 to July 1952, and the results are found inYstad [12] andStr?m [8, 9, 10, 11]. On 25 February 1971 some water samples were taken from R?rholtfjorden to supply the information from the lake, and if possible record changes in the water for the last 20 years. The tables contain chemical data, pH, temperature and oxygen content. The trapped sea-water is also compared with original sea-water with the same chloride content. It is difficult to say anything about changes in the salt-water because of uncertainty regarding the depth measurements. But a so-called semi-stagnation (Str?m [8]) was not observed (Fig. 3). It is possible that about one meter of the trapped sea-water has been lost during the last 20 years because of the removed semi-stagnation.

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Zusammenfassung Im R?rholtfjord, Telemark, Norwegen, wurde 1951 von?smund Ystad, Universit?t Oslo, ?gefangenes? Meerwasser entdeckt, welches dann von August 1951 bis Juli 1952 kontinuierlich untersucht wurde. Die Resultate sind beiYstad [12] undStr?m [8, 9, 10, 11] publiziert. Im February 1971 wurden erneut Proben aus dem Fjord genommen, um eventuelle Ver?nderungen w?hrend der vergangenen 20 Jahre festzustellen. Es wurden chemische Daten sowie pH, Temperatur und O₂-Gehalt aufgenommen. Das ?gefangene? Wasser wurde auch mit Originalmeerwasser derselben Salinit?t verglichen. Wegen der Ungenauigkeit der Tiefenmessungen ist es schwierig, etwas über Ver?nderungen auszusagen. Indessen wurde eine sog. Semi-Stagnation, wie sieStr?m [8] beschreibt, nicht beobachtet (Fig. 3). M?glicherweise ging etwa 1 m des ?gefangenen? Wassers zufolge des Verschwindens jener Semi-Stagnation verloren.

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Résumé De l’eau de mer ?captivée? dans le R?rholtfjord, Telemark, Norvège, fut découverte en 1951 par?smund Ystad, étudiant en Limnologie à l’Université d’Oslo. Des expériences avec l’eau de ce lac ont été poursuivies continuellement d’ao?t 1951 à juillet 1952 et les résultats ont été publiés parYstad [12] etStr?m [8, 9, 10, 11]. Le 25 février 1971, de nouveaux échantillons d’eau ont été prélevés dans le fjord pour étudier si, dans les 20 dernières années, d’éventuels changements étaient survenus. Les tableaux présentés contiennent les données chimiques, ainsi que le pH, la température et le taux d’oxygène. En plus, l’eau ?captivée? est comparée avec l’eau de mer originale, au même taux de salinité. Il est difficile de s’exprimer sur les changements survenus dans l’eau, à cause de l’incertitude concernant les mesures de profondeur. Cependant, on n’a pas observé une dite semi-stagnation comme l’a décriteStróm [8] (fig. 3). Il est possible qu’environ un mètre de cette eau ?captivée? se soit perdue, durant les 20 dernières années, par la disparition de la semi-stagnation.

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Long-term effects of anthropogenic CO<Subscript>2</Subscript> emissions simulated with a complex earth system model     

Uwe Mikolajewicz  Matthias Gröger  Ernst Maier-Reimer  Guy Schurgers  Miren Vizcaíno  Arne M. E. Winguth 《Climate Dynamics》2007,28(6):599-633

A new complex earth system model consisting of an atmospheric general circulation model, an ocean general circulation model, a three-dimensional ice sheet model, a marine biogeochemistry model, and a dynamic vegetation model was used to study the long-term response to anthropogenic carbon emissions. The prescribed emissions follow estimates of past emissions for the period 1751–2000 and standard IPCC emission scenarios up to the year 2100. After 2100, an exponential decrease of the emissions was assumed. For each of the scenarios, a small ensemble of simulations was carried out. The North Atlantic overturning collapsed in the high emission scenario (A2) simulations. In the low emission scenario (B1), only a temporary weakening of the deep water formation in the North Atlantic is predicted. The moderate emission scenario (A1B) brings the system close to its bifurcation point, with three out of five runs leading to a collapsed North Atlantic overturning circulation. The atmospheric moisture transport predominantly contributes to the collapse of the deep water formation. In the simulations with collapsed deep water formation in the North Atlantic a substantial cooling over parts of the North Atlantic is simulated. Anthropogenic climate change substantially reduces the ability of land and ocean to sequester anthropogenic carbon. The simulated effect of a collapse of the deep water formation in the North Atlantic on the atmospheric CO₂ concentration turned out to be relatively small. The volume of the Greenland ice sheet is reduced, but its contribution to global mean sea level is almost counterbalanced by the growth of the Antarctic ice sheet due to enhanced snowfall. The modifications of the high latitude freshwater input due to the simulated changes in mass balance of the ice sheet are one order of magnitude smaller than the changes due to atmospheric moisture transport. After the year 3000, the global mean surface temperature is predicted to be almost constant due to the compensating effects of decreasing atmospheric CO₂ concentrations due to oceanic uptake and delayed response to increasing atmospheric CO₂ concentrations before.  相似文献