Sentences with phrase «lighter isotopic»

Methane produced by these microbial communities tends to have a lighter isotopic signature than that produced by other means, such as fossil fuel burning.

The results, published online today in Science, reveal that the inclusions have a much lighter isotopic signature than does the ocean, suggesting that the composition of seawater has indeed evolved over time.

And Hallis suspects that the deepest, most primitive material in the mantle should have an even lighter isotopic composition than the inclusions her team measured.

Not exact matches

Because life prefers lighter carbon, the isotopes suggest to some scientists that the atmospheric rise must be due to extra microbial production, and not a boost due to leaked gas from fracking operations, which has a heavier isotopic signature.

Based on measurements of Jupiter and the solar wind, which are thought to preserve the hydrogen isotopic ratio of the protosolar nebula, scientists think nebular water had an extremely light hydrogen isotopic signature — much closer to what the Baffin Island lavas suggest about the deep mantle's water.

And then, if the ocean surface water was «diluted» with isotopic light melt water, would this not be reflected with a similar drop in the Greenland ice cores, just by a changing isotope signature of the source, instead of a temperature drop?

Because carbon cycle processes such as photosynthesis fractionate the heavy isotope 13C from the lighter 12C, isotopic analysis can usually be used to «trace» sources and sinks of carbon.

And then, if the ocean surface water was «diluted» with isotopic light melt water, would this not be reflected with a similar drop in the Greenland ice cores, just by a changing isotope signature of the source, instead of a temperature drop?

[Response: If the rise in atmospheric CO2 at the end of the last glacial time had come from organic carbon (trees, peat, dissolved organic matter in the ocean) or especially methane (which is even more isotopically «light» than CO2) it would have left an isotopic signature.

point out that isotopic composition of airborne methane has become lighter since 2008, indicating greater wetland / ruminant emission.

[Response: My recollection is that Zachos had the same observation from ODP cores, that surface - dwelling forams were either isotopically heavy or light, never transitional, but bottom - dwellers could be found with transitional isotopic composition.

«THE stable carbon isotopic (13C / 12C) record of twentieth - century tree rings has been examined1 - 3 for evidence of the effects of the input of isotopically lighter fossil fuel CO2 (δ 13C ~ -25 ‰ relative to the primary PDB standard4), since the onset of major fossil fuel combustion during the mid-nineteenth century, on the 13C / 12C ratio of atmospheric CO2 (δ 13C ~ -7 ‰), which is assimilated by trees by photosynthesis.

Empirically and theoretically, isotopic composition of precipitation and site temperature are strongly correlated in time and space (10, 11); colder places and colder times have isotopically lighter precipitation.»

The methane produced by the burning of biomass, like wood, contains more of the heavier isotope (carbon - 13) relative to the lighter isotope (carbon - 12), than methane which is produced in wetlands,» explains Professor Thomas Blunier, Centre for Ice and Climate at the Niels Bohr Institute at the University of Copenhagen.The researchers have measured the isotopic composition of the methane in ice cores that are drilled up from the Greenland ice cap at the NEEM project in northwestern Greenland.