Sentences with phrase «isotope ratios over»
When the researchers analyzed the oxygen isotope ratios over the past 8,000 years, they found that the jet stream became wavier — with colder Eastern winter weather and warmer Western winter weather — on about a 4,000 - year cycle.
https://www.scientificamerican.com/ Not exact matches
The calorie reductions were calculated individually through the ratio of isotopes absorbed by the participants» molecules and tissues over 2 weeks, a technique that accurately pinpoints a weight - maintenance calorie level.
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.
Nitrogen isotope ratios can be used to estimate the change in the amount of bioavailable nitrogen over time.
Then they measured those two isotopes in the apes» urine to see how the ratio changed over time.
As photosynthesis favours the lighter isotope, carbon 12, over the heavier carbon 13, this «light» ratio finding suggests that organic material from biological sources may have been more abundant in diamond - forming zones early in the Earth's history than we find today,» explained Suzette Timmerman, lead author on the study.
In 1995 U.S. researchers found that carbon isotope ratios in elephants at Amboseli National Park in Kenya had shifted over decades, reflecting changes in the elephants» diet as they crowded into the park to escape poaching, ate up the park's trees, and switched to grass.
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.
The prevalences and isotope ratios of the noble, or inert, gases, such as neon, argon, krypton and xenon, provide a valuable tracer of ancient processes, because they are chemically nonreactive and so do not change much over time.
Extrapolating from their isotope ratios, the authors conclude that, over the 9 month period, the lions probably consumed around 10.5 and 24.2 humans, respectively, or around 35 humans total.
Analyzing the ratios between two Strontium isotopes, 87Sr and 86Sr, researchers can determine differences from place to place on the landscape so uptake of Strontium over a wide area can be distinguished from uptake over a small area.
About 10 years ago the certainly over the anthropogenic carbon dioxide was firmly fixed by isotope ratios.
As such, assigning anthropogenic causation to C13 / C12 Isotope ratios is highly suspect, and furthermore Wei et al. only found increasing trends «over the past 60 years».
The ratios of input and atmospheric isotopes converge over time.
While there are alternative explanations for the ratios over shorter periods, I remain very doubtful on the possibility of fitting the history of the isotope ratios to any alternative theory that includes the large changes in natural fluxes that are required to make human influence less than dominant factor.
Discussions of isotope ratios and uptake and emission of CO2 by all the various and sundry physical and biological processes are distractions to the simplest and most compelling line of evidence that the increase in atmospheric CO2 concentrations is primarily anthropogenic — to wit, comparing the expected concentration increase based on anthropogenic emission rates with the actual increase over a given period of time.
Scientists also found the ratio of carbon isotopes in the atmosphere to be changing over time due to our use of fossil fuels.
No need to get sidetracked by isotope ratios, natural sinks and sources, paleoclimatic conditions, etc. — Heck, you don't even have to worry about what the actual pre-industrial average was since we are only looking at the change over a given period of time.
Distributions of biota in soil at various altitudes and latitudes over time, isotope ratios, and so forth might with a global effort create an effective grid that could reconstruct a fraction of what has been lost.
Global, cyclic, decadal, climate patterns can be traced over the past millennium in glacier fluctuations, oxygen isotope ratios in ice cores, sea surface temperatures, and historic observations.