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1.
The ratios of oxygen-18 to oxygen-16 and of carbon-13 to carbon-12 in the early shell and septa of two Nautilus specimens are interpreted for the early ontogeny of the animals. Changes in the carbon isotope content are tentatively correlated with the end of the embryonic period and with environmental changes. Variations in the oxygen isotope content are in part ascribed to migrations from warm to cooler water after a certain stage of development. The size of the body chamber of the young animals can be determined by comparison of the isotope contents in outer shell and septa. 相似文献
2.
Samples of marine shell from archeological context on the coast of Nayarit, Mexico, have given radiocarbon determinations of 1810 +/- 80 B.C., 2000 +/- 100 B.C., and 2100 +/- 100 B.C. Even with maximum correction for upwelling these are the earliest dates for coastal occupation in West Mexico north of Acapulco, Guerrero. Analysis of the midden contents has provided new insights regarding early coastal adaptation. 相似文献
3.
Three-dimensional, spherical models of mantle convection in the earth reveal that upwelling cylindrical plumes and downwelling planar sheets are the primary features of mantle circulation. Thus, subduction zones and descending sheetlike slabs in the mantle are fundamental characteristics of thermal convection in a spherical shell and are not merely the consequences of the rigidity of the slabs, which are cooler than the surrounding mantle. Cylindrical mantle plumes that cause hotspots such as Hawaii are probably the only form of active upwelling and are therefore not just secondary convective currents separate from the large-scale mantle circulation. Active sheetlike upwellings that could be associated with mid-ocean ridges did not develop in the model simulations, a result that is in agreement with evidence suggesting that ridges are passive phenomena resulting from the tearing of surface plates by the pull of descending slabs. 相似文献
4.
Andrus CF Crowe DE Sandweiss DH Reitz EJ Romanek CS 《Science (New York, N.Y.)》2002,295(5559):1508-1511
Peruvian sea catfish (Galeichthys peruvianus) sagittal otoliths preserve a record of modern and mid-Holocene sea surface temperatures (SSTs). Oxygen isotope profiles in otoliths excavated from Ostra [6010 +/- 90 years before the present (yr B.P.); 8 degrees 55'S] indicate that summer SSTs were approximately 3 degrees C warmer than those of the present. Siches otoliths (6450 +/- 110 yr B.P.; 4 degrees 40'S) recorded mean annual temperatures approximately 3 degrees to 4 degrees C warmer than were measured under modern conditions. Trophic level and population diversity and equitability data from these faunal assemblages and other Peruvian archaeological sites support the isotope interpretations and suggest that upwelling of the Peru-Chile current intensified after approximately 5000 yr B.P. 相似文献
5.
头足类硬组织的稳定同位素研究进展 总被引：2，自引：2，他引：0
头足类作为一种重要的海洋无脊椎动物,在世界海洋生态系统中扮演着非常重要的角色。而目前对其捕食活动和摄食情况的研究不多。稳定同位素作为新型应用技术,被广泛应用于生态系统的研究中。头足类作为捕食者,其体内有大量的碳(C)、氮(N)、氧(O)等稳定同位素,且其硬组织是稳定同位素积累的优良载体,因此通过稳定同位素示踪的方法,分析硬组织各部位稳定同位素含量及其分布,可为了解头足类在海洋生态系统中所处的地位提供手段和方法。根据国内外研究现状,重点分析了耳石、角质额和内壳等硬组织稳定同位素在头足类摄食生态中的应用,并进行了总结和归纳,同时对今后的研究提出了建议。 相似文献
6.
The oceans play a major role in defining atmospheric carbon dioxide (CO2) levels, and although the geographical distribution of CO2 uptake and release in the modern ocean is understood, little is known about past distributions. Boron isotope studies of planktonic foraminifera from the western equatorial Pacific show that this area was a strong source of CO2 to the atmosphere between approximately 13,800 and 15,600 years ago. This observation is most compatible with increased frequency of La Ni?a conditions during this interval. Hence, increased upwelling in the eastern equatorial Pacific may have played an important role in the rise in atmospheric CO2 during the last deglaciation. 相似文献
7.
The occurrence of carbon isotope minima at the beginning of glacial terminations is a common feature of planktic foraminifera carbon isotopic records from the Indo-Pacific, sub-Antarctic, and South Atlantic. We use the delta13C record of a thermocline-dwelling foraminifera, Neogloboquadrina dutertrei, and surface temperature estimates from the eastern equatorial Pacific to demonstrate that the onset of delta13C minimum events and the initiation of Southern Ocean warming occurred simultaneously. Timing agreement between the marine record and the delta13C minimum in an Antarctic atmospheric record suggests that the deglacial events were a response to the breakdown of surface water stratification, renewed Circumpolar Deep Water upwelling, and advection of low delta13C waters to the convergence zone at the sub-Antarctic front. On the basis of age agreement between the absolute delta13C minimum in surface records and the shift from low to high delta13C in the deep South Atlantic, we suggest that the delta13C rise that marks the end of the carbon isotope minima was due to the resumption of North Atlantic Deep Water influence in the Southern Ocean. 相似文献
8.
HP Bunge MA Richards C Lithgow-Bertelloni JR Baumgardner SP Grand BA Romanowicz 《Science (New York, N.Y.)》1998,280(5360):91-95
Computer models of mantle convection constrained by the history of Cenozoic and Mesozoic plate motions explain some deep-mantle structural heterogeneity imaged by seismic tomography, especially those related to subduction. They also reveal a 150-million-year time scale for generating thermal heterogeneity in the mantle, comparable to the record of plate motion reconstructions, so that the problem of unknown initial conditions can be overcome. The pattern of lowermost mantle structure at the core-mantle boundary is controlled by subduction history, although seismic tomography reveals intense large-scale hot (low-velocity) upwelling features not explicitly predicted by the models. 相似文献
9.
The shells of large benthic foraminifera contain a record of seasonal temperature ranges and life history stages. Marginopora vertebralis and Cyclorbiculina compressa show distinct differences in life history, growth rate history, and life-span, as reflected in stable isotope patterns within their shells. 相似文献
10.
LT Toth RB Aronson SV Vollmer JW Hobbs DH Urrego H Cheng IC Enochs DJ Combosch R van Woesik IG Macintyre 《Science (New York, N.Y.)》2012,337(6090):81-84
Cores of coral reef frameworks along an upwelling gradient in Panamá show that reef ecosystems in the tropical eastern Pacific collapsed for 2500 years, representing as much as 40% of their history, beginning about 4000 years ago. The principal cause of this millennial-scale hiatus in reef growth was increased variability of the El Ni?o-Southern Oscillation (ENSO) and its coupling with the Intertropical Convergence Zone. The hiatus was a Pacific-wide phenomenon with an underlying climatology similar to probable scenarios for the next century. Global climate change is probably driving eastern Pacific reefs toward another regional collapse. 相似文献
11.
Schmitt J Schneider R Elsig J Leuenberger D Lourantou A Chappellaz J Köhler P Joos F Stocker TF Leuenberger M Fischer H 《Science (New York, N.Y.)》2012,336(6082):711-714
The stable carbon isotope ratio of atmospheric CO(2) (δ(13)C(atm)) is a key parameter in deciphering past carbon cycle changes. Here we present δ(13)C(atm) data for the past 24,000 years derived from three independent records from two Antarctic ice cores. We conclude that a pronounced 0.3 per mil decrease in δ(13)C(atm) during the early deglaciation can be best explained by upwelling of old, carbon-enriched waters in the Southern Ocean. Later in the deglaciation, regrowth of the terrestrial biosphere, changes in sea surface temperature, and ocean circulation governed the δ(13)C(atm) evolution. During the Last Glacial Maximum, δ(13)C(atm) and atmospheric CO(2) concentration were essentially constant, which suggests that the carbon cycle was in dynamic equilibrium and that the net transfer of carbon to the deep ocean had occurred before then. 相似文献
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13.
利用2002-2013年期间的卫星遥感海表温度(SST)数据分析了舟山海域夏季上升流的时空特征,并结合同时期的海面风场数据探讨了风对该海域夏季上升流的影响。对多年夏季月平均的SST进行经验正交函数(EOF)分解结果表明,7月份前两个模态方差贡献率分别为71.66%、16.55%,8月份前两个模态方差贡献率分别为87.03%和7.30%,并均通过了显著性检验,舟山近海海域的上升流存在较为明显的年际变化。相关分析显示,经向风速和SST异常存在显著的负相关关系,即夏季盛行的西南风有利于上升流的发展。并且,艾克曼(Ekman)体积输运计算结果表明,舟山海域7、8月份风生上升流的量级分别为3.0×10~(-5)m/s和1.5×10~(-5)m/s,7月上升流显著强于8月,这与8月份观测到的海表显著低温异常相关。 相似文献
14.
Ward PD Haggart JW Carter ES Wilbur D Tipper HW Evans T 《Science (New York, N.Y.)》2001,292(5519):1148-1151
The end-Triassic mass extinction is one of the five most catastrophic in Phanerozoic Earth history. Here we report carbon isotope evidence of a pronounced productivity collapse at the boundary, coincident with a sudden extinction among marine plankton, from stratigraphic sections on the Queen Charlotte Islands, British Columbia, Canada. This signal is similar to (though smaller than) the carbon isotope excursions associated with the Permian-Triassic and Cretaceous-Tertiary events. 相似文献
15.
The isotope record of sedimentary sulfides can help resolve the history of oxygen accumulation into the atmosphere. We measured sulfur isotopic fractionation during microbial sulfate reduction up to 88 degrees C and show how sulfate reduction rate influences the preservation of biological fractionations in sediments. The sedimentary sulfur isotope record suggests low concentrations of seawater sulfate and atmospheric oxygen in the early Archean (3.4 to 2.8 billion years ago). The accumulation of oxygen and sulfate began later, in the early Proterozoic (2.5 to 0.54 billion years ago). 相似文献
16.
The size of the marine sulfate reservoir has grown through Earth's history, reflecting the accumulation of oxygen into the atmosphere. Sulfur isotope fractionation experiments on marine and freshwater sulfate reducers, together with the isotope record, imply that oceanic Archean sulfate concentrations were <200 microM, which is less than one-hundredth of present marine sulfate levels and one-fifth of what was previously thought. Such low sulfate concentrations were maintained by volcanic outgassing of SO2 gas, and severely suppressed sulfate reduction rates allowed for a carbon cycle dominated by methanogenesis. 相似文献
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18.
Kidwell SM 《Science (New York, N.Y.)》2005,307(5711):914-917
A major suspected bias in the fossil record of skeletonized groups is variation in preservability owing to differences in shell composition. However, despite extensive changes in shell composition over the 500-million-year history of marine bivalves, genus duration and shell composition show few significant relationships, and of those, virtually all are contrary to bias from preferential loss of highly reactive shell types. Distortion of large-scale temporal patterns in marine bivalves owing to preservability is thus apparently weak or randomly distributed, which increases the likelihood that observed patterns in this and other shelled groups carry a strong biological signal. 相似文献
19.
Bakun A 《Science (New York, N.Y.)》1990,247(4939):198-201
A mechanism exists whereby global greenhouse warning could, by intensifying the alongshore wind stress on the ocean surface, lead to acceleration of coastal upwelling. Evidence from several different regions suggests that the major coastal upwelling systems of the world have been growing in upwelling intensity as greenhouse gases have accumulated in the earth's atmosphere. Thus the cool foggy summer conditions that typify the coastlands of northern California and other similar upwelling regions might, under global warming, become even more pronounced. Effects of enhanced upwelling on the marine ecosystem are uncertain but potentially dramatic. 相似文献
20.
眼睛晶体作为鱼类的硬组织之一,具有结构稳定、耐腐蚀、易获取的特性,其含有大量的蛋白质,蕴含着丰富的化学信息,并在鱼类的年龄鉴定中得到了一定程度的应用。近年来,随着生物地球化学技术的不断创新与进步,鱼类眼睛晶体的微量元素、稳定同位素信息也越来越受到国内外学者的重视。本文将依据国内外学者的研究成果,从眼睛晶体的直径与重量、微结构、微量元素和稳定同位素等方面,对鱼类的年龄鉴定、栖息环境重建、摄食生态的追踪等方面的应用进行综述,并通过分析鱼类眼睛晶体的组成成分与生长模式,比较眼睛晶体与其他组织做稳定同位素分析的优势,着重归纳总结了眼睛晶体碳氮稳定同位素在鱼类生活史信息,尤其在摄食生态、栖息环境重建等方面的研究方法、应用现状及发展前景,为以后开展相关的研究提供参考。 相似文献