Sentences with phrase «of oxygen isotope ratios»
The team used records of oxygen isotope ratios (which provide a record of ancient water temperature) from microscopic plankton fossils recovered from the Mediterranean Sea, spanning the last 5.3 million years.
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But the team's measurements of the oxygen isotope ratios in the creatures» teeth, a sensitive paleo - thermometer, suggest that the climate where these dinosaurs lived probably averaged about 10 ° Celsius over the course of a year — substantially colder than most of the dinosaur era, and in fact close to that seen in northeastern China today, Xu notes.
The principal dataset we use is the temporal variation of the oxygen isotope ratio (δ18O relative to δ16O; figure 1a right - hand scale) in the shells of deep - ocean - dwelling microscopic shelled animals (foraminifera) in a near - global compilation of ocean sediment cores [4].
Not exact matches
The ratio of oxygen isotopes in seawater depends on the water temperature; the value of this ratio at any point in evolutionary time is «frozen» into the chemical composition of certain marine fossils.
The ratio of strontium to calcium in a given layer of coral reef — as well as the amount of a heavier isotope of oxygen in the carbonate itself — reflect the temperature in this historical record, but the isotopic information also reveals rainfall.
When the jet stream got loopy In order to track the jet stream's behavior thousands of years ago, Bowen and his fellow researchers looked at oxygen isotope ratios from lake cores and cave formations in the eastern and western United States.
They then compared the oxygen isotope ratio in Yonderup dripwater with that predicted by a model (which simulated the dripwater δ18O based on measurements of rainwater δ18O), as well as that measured at a different cave in the region.
The researchers determined from the isotope ratio that the Taylor Glacier samples were 120,000 years old, and validated the estimate by comparing the results to well - dated ice core measurements of atmospheric methane and oxygen from that same period.
It is measurable in terms of oxygen and carbon isotope ratios and was compared to «environmental archive» data from other parts of the earth.
The ratio of two oxygen isotopes in the larch's cellulose would give Ballantyne a temperature range.
Barrick and Showers measured the relative ratios of the isotopes oxygen - 16 and oxygen - 18 in the phosphate from 54 samples of a near - complete T. rex skeleton.
Nevertheless, some scientists claim that ratios of oxygen isotopes in marine fossils from the east coast of the US indicate that the Antarctic ice sheet melted at least partially during the Pliocene.
As the 2 - to -5-inch-long bivalves grew, their shells incorporated atoms of the elements oxygen and carbon of slightly different masses, or isotopes, in ratios that reveal the temperature of the surrounding seawater.
David Hodell, Jason Curtis and Mark Brenner from the University of Florida obtained their evidence from the ratio of calcium carbonate to calcium sulphate in sediments from Lake Chichancanab, in Yucátan, Mexico, and from the proportion of heavy to light isotopes of oxygen in buried shells.
The team based its analysis on ratios of oxygen and hydrogen isotopes in ice cores drilled in East Antarctica.
To better understand the cycle of magma production, the researchers analyzed oxygen isotope ratios in quartz and zircon, water - and heat - resistant minerals, from volcanic rocks in the Yellowstone caldera.
The ratio of oxygen - 18, a rare isotope, to ordinary oxygen - 16, was considerably higher in the stone than the ratio found in Earth's mantle.
These spectra also indicated the ratio of oxygen isotopes in Vesta's rocks.
By applying uranium - thorium dating to the corals and measuring ratios of oxygen isotopes in their skeletons, her lab reconstructed ocean temperatures for much of the last 7000 years.
The Earth's water must have come from its interior, according to a scientist who has studied the ratios of oxygen isotopes in rocks.
Karlos Muehlenbachs of the University of Alberta measured the ratio of oxygen isotopes in the oldest rocks known on Earth, which formed 3.96 billion years ago.
Environmental scientist Suzanna Richter and plant physiological ecologist Brent Helliker, both at the University of Pennsylvania, measured the ratio of two isotopes of oxygen — rarer oxygen - 18 and more common oxygen - 16 — in samples of wood.
The new findings on Arctic Ocean salinity conditions in the Eocene were calculated in part by comparing ratios of oxygen isotopes locked in ancient shark teeth found in sediments on Banks Island in the Arctic Circle and incorporating the data into a salinity model.
Back at their Georgia Tech lab, they analyzed the stalagmites for the ratio of oxygen isotopes contained in samples of calcium carbonate, the material from which the stalagmites were formed.
The researchers could tell that seeds had been deposited higher up the mountain than they had been harvested by the ratio of their oxygen isotopes, which changes with altitude.
In addition, Valley and his group measured oxygen isotope ratios, which give evidence of early homogenization and later cooling of the Earth.
The most convincing evidence for this, says Jouzel, comes from isotope ratios; ice that has frozen in site has a higher proportion of water molecules containing the heavy form of oxygen, oxygen - 18, than that of ice that has been transported over long distances by weather systems.
Oxygen isotope ratios in carbonate sediments are correlated with the ratio of precipitation to evaporation and thus indicate aridity.
Dust from our own solar system has a characteristic ratio of heavy to light oxygen isotopes.
The information about oxygen concentration comes from the isotopic composition of carbon or rather from the ratio between the stable carbon isotopes 12C and 13C.
The heavier oxygen isotope ratio varies dependent upon the difference in vapour pressure due to the different atomic weights of normal and heavy oxygen based water.
To date, we have a full complement of analyses for about three years of growth for one tusk from the Taimir Peninsula of Siberia (the Jarkov mammoth; ca. 20,300 rybp) and growth increment and tusk apatite carbon and oxygen isotope ratios for two to three years of growth from two tusks from Wrangel Island (4,400 and 4,120 year bp).
u «The moon rocks, however, showed [oxygen isotope] ratios markedly similar to those of rocks from Earth.
«Scientists use the ratio of the various sulfur isotopes as their strongest evidence for atmospheric oxygen.»
Because of the rapid growth rate of the snails, which are a widespread invasive species in India, moisture - sensitive oxygen isotope ratios in growth bands in the animals» shells preserve week - to - week rainfall rates, the researchers found.
They limited data sources to locations around the world in which paleoceanographic data also exist, using seven variables: salinity; potential temperature; oxygen isotope ratios in water; carbon isotope ratios in dissolved inorganic carbon; and concentrations of phosphate, nitrate, and dissolved oxygen.
The glaciation was favored by an interval when the Earth's orbit favored cool summers but Oxygen isotope ratio cycle marker changes were too large to be explained by Antarctic ice - sheet growth alone indicating an ice age of some size.
One group of students has been drilling modern and fossil teeth to obtain samples that will be analyzed to examine stable carbon and oxygen isotope ratios.
Oxygen isotope ratios (δ18O) in polar snow are well known to be correlated with temperature, and the underlying physics of the relationship is very well understood.
To date, we have a full complement of analyses for about three years of growth for one tusk from the Taimir Peninsula of Siberia (the Jarkov mammoth; ca. 20,300 rybp) and growth increment and tusk apatite carbon and oxygen isotope ratios for two to three years of growth from two tusks from Wrangel Island (4,400 and 4,120 year bp).
In particular, the oxygen isotope ratios can reveal that a hurricane has occurred, but as far as I can see give little indication of strength.
That seems a way more satisfactory approach than the crude estimate in Hansen et al (2013) that I've been using, which relies on an interpretive leap from a deep water temperature proxy (oxygen isotope ratios from the microscopic shells of bottom - dwelling marine critters).
Like the data used right through 0.02 to 66 My, the Freidrich et al collection comprises stable oxygen isotope ratios from the shells of tiny bottom - dwelling, deep - water marine organisms (benthic foraminifera).
The scientists examined surveys of the ratio of strontium to calcium content and heavy oxygen isotopes, both are sensitive recorders of sea surface temperatures past and present.
The scientists analyzed the ratio of the oxygen isotopes in the hydration water and in the calcium carbonate.
For decades, scientists studying climate change have measured the oxygen isotope ratio in tree - ring cellulose to determine the ambient temperature and relative humidity of past climates.
The group highlighted the added value of measuring paired coral strontium / calcium ratios (Sr / Ca) and oxygen isotope ratios (δ18O), two key proxies for sea surface temperature that are often referred to as paleothermometers (δ18O also reflects sea surface salinity).
The temperature is measured by the the oxygen isotope ratio, which we recently learned is the temperature of the leaves, and the leaves tend to keep a constant temperature.
Rainfall from cyclones contains relatively little heavy oxygen so analysing the oxygen isotope ratio of calcite in stalagmites can reveal the extent of cyclone activity.
The team then compared the oxygen isotope ratio for each year's wet season from 1990 to 2010 with a cyclone activity index of the average accumulated energy expended, based on factors such as number of cyclones, cyclone strength, size and time on storm track.