Fractionation mechanism of stable isotope in evaporating water body
China ; Evaporation ; Isotope analysis ; Lake ; Moisture ; Simulation ; Temperature ; Tibet ; Water cycle
This study quantificationally analyses the interaction between evaporating water body and atmosphere, and the influences of different factors on the evaporation by probing into the fractionation mechanism of stable isotope as water body is vaporized
A review of various factors influencing the stable carbon isotope ratio of organic lake sediments by the change from glacial to post-glacial environmental conditions
The AA. present the preliminary results of measurements of diurnal changes in the isotopic composition of atmospheric CO2 in Kraków. They present four experiments done in different seasons of the year. Results show that the isotope composition
This paper assesses the preservation of biogenic isotopic composition of the collagen fraction of mammal bone and tooth from the uppermost well-defined layer of the cave (numbered 1A) and determines the ecological basis for interspecific differences
in the carbon and nitrogen isotopic compositions of mammals from other late Pleistocene sites in Eurasia.
Chronology and paleohydrology of Late Quaternary high lake levels in the Manyara Basin (Tanzania) from isotopic data (18O, 13C, 14C, Th/U) on fossil stromatolites
Dating ; Isotope ; Lake level ; Palaeogeography ; Palaeohydrology ; Quaternary ; Tanzania
In this article, new isotopic data on the hydrology and paleohydrology of the Lake Manyara basin are presented. They complement previous studies on lakes Natron and Magadi, to the north, and provide additional information on late Pleistocene
The AA. examine evidence for climatic change at the Aubrey Clovis site, north-central Texas, over the past 14,000 yr. The primary emphasis of this paper will be on stable isotopic evidence from pedogenic and lacustrine carbonates from the study site
. An indepedently derived alluvial history from the same locality corroborate the isotopic data.
Structure and timing of the last deglaciation : oxygen-isotope evidence
Foraminiferal oxygen-isotope data from 24 Tropical Atlantic sediment cores, constrained by 77 14 C dates, are stacked to form a composite record of isotopic Termination 1. This record indicates that most of the isotopic transition at the end
Carbon isotopic changes in benthic foraminifera from the western South Atlantic: reconstruction of glacial abyssal circulation patterns
Analyse isotopique ; Atlantique ; Atlantique Sud ; Circulation abyssale ; Foraminifère benthique ; Géographie physique ; Isotope O18-O16 ; Isotopes du carbone ; Océan ; Paléohydrologie ; Pléistocène supérieur ; Quaternaire marin ; Rio Grande ; Vema
Oxygen-and carbon-isotopic analyses have been performed on the benthic foraminifer Planulina wuellerstorfi in seven Late Quaternary cores from the Vema ChannelRio Grande Rise region.
An isotopic study of paleosol carbonates from Olduvai gorge
The isotopic composition (oxygen and carbon isotopes) of paleosol carbonates is used to give estimates of the paleoclimatic history of East Africa during the Plio-Pleistocene. Three major periods of climatic change in this terrestrial setting
occurred at about 1.67, 1.3 and 0.6 myr. These involved major changes in flora as well as major changes in the isotopic composition of meteoric water. Overall, the climate has become warmer and more arid over the part 2.2 myr.
Environmental isotopes, such as oxygen-18 and deuterium, have been used increasingly to separate stormflow into its event and pre-event components in order to elucidate the sources, pathways and residence times of water in drainage basins
. The hydrological processes that have been invoked to explain the observed isotopic response of streamflow to rainfall and snowmelt inputs in various environments are reviewed. This paper summarizes the environmental isotope hydrograph separation technique
and provides a broad review of the results of isotope hydrograph separations conducted around the world.
Messungen des Gehalts an stabilen Isotopen in einer temperierten randalpinen Schneedecke Measurements of the content of stabil isotopes in a temperated cover on border areas of the Alpes
During the ablation period of 1974, the content of deuterium and oxygen-18 in snow was measured, sampled at the layers of an open area lysimeter snow cover at 1030 m a.s.l. Changes in isotope concentrations are subject to the influence of melt
-and rainwater percolation through the snow cover, but also to evaporation and condensation processes. Abrupt, short-termed alterations of isotopic contents are discussed as well as the isotopic balance and deuterium-oxygen-18 relations. (HSC).
A detailed 31,000-year record of climate and vegetation change, from the isotope geochemistry of two New Zealand speleothems
Carbon ; Cave ; Glaciation ; Isotope analysis ; New Zealand ; Oxygen 18 ; Palaeo-environment ; Palaeobotany ; Palaeoclimate ; Pleistocene ; Quaternary ; South Island
This paper presents continuous high-resolution stable isotope records of environmental change in New Zealand from speleothems that grew over the last 31,000 yr. Oxygen isotope variation in these speleothems primarily represents changes
in the meteoric waters falling above the caves, possibly responding to latitudinal changes in the position of the Subtropical Front in the Tasman sea. Carbone isotope variations in the speleothems record changes in forest productivity, closely matching existing
Holocene paleohydrology and paleoclimate at treeline, North-Central Russia, inferred from oxygen isotope records in lake sediment cellulose
The AA. use lake-water oxygen-isotope histories, inferred from stratigraphic analysis of cellulose in the fine-grained fraction of lake-sediment cores, to reconstruct Holocene paleohydrology at the boreal treeline near the lower Yenisey and Lena
Rivers of northern Russia. These studies are supplemented by isotopic analysis of samples of modern meteoric water, including precipitation, groundwater, and ground-ice, which provide insight into the modern isotope hydrology. The isotopic records
Late Quaternary climate and hydrology of tropical South America inferred from an isotopic and chemical model of Lake Titicaca, Bolivia and Peru
Bolivia ; Climatic variation ; Geochemistry ; Isotope analysis ; Lake ; Lake level ; Model ; Oxygen 18 ; Palaeoclimate ; Palaeohydrology ; Peru ; Quaternary ; Salinity ; South America ; Tropical zone
A simple mass balance model provides insight into the hydrologic, isotopic, and chemical responses of Lake Titicaca to past climatic changes. Latest Pleistocene climate of the Altiplano is assumed to have been 20% wetter and 5°C colder than today
, based on previous modelling. The simulation of lacustrine change since 15,000 cal yr B.P. is forced by these modeled climate changes. Here the AA. employ an isotopic and chemical model in order to assess the magnitude of hydrologic changes required
to produce the observed lake-level changes and to investigate the expected isotopic and chemical response of the lake to water balance changes.
Oxygen-isotope analyses and Pleistocene ice volumes
The oxygen-isotope record from fossil foraminifera in deep-sea sediments is commonly used as a proxy for global ice volume. The linkage between O and ice volume, however, is probably nonlinear. The AA. have developed a simple numerical model
of the isotopic response of the oceans to ice-volume change. They illustrate the response of their model to simple hypothetical ice-volume transitions of ice growth and ice decay. Sensitivity tests are illustrated for all model parameters. The results suggest
that oxygen-isotope records reproduce the general patterns on ice-volume change fairly accurately. The foraminiferal isotope record, however, may misrepresent the true amplitude of the ice-volume signal and lag true ice volume by 1000 to 3000 yr.