The mechanistic understanding of isotope fractionation processes is increasing but we still lack detailed knowledge of the processes that determine the isotopic composition of the tree-ring archive over the long term. Especially with regard to the path from leaf photosynthate production to wood formation, post-assimilation fractionations/processes might cause at least a partial decoupling betwe...

A one-dimensional chemistry model is applied to study the stable hydrogen (D) and stable oxygen isotope (17O, 18O) composition of water vapour in stratosphere and mesosphere. In the troposphere, this isotope composition is determined by “physical” fractionation effects, that are phase changes (e.g. during cloud formation), diffusion processes (e.g. during evaporation from the ocean), and mixing...

drich, P Jenniskens, and M. H. Shaddad, Geophysical Laboratory, Carnegie Institution, Washington, DC 20015 ([email protected]), NASA Johnson Space Flight Center, 2101 NASA Parkway, Houston, TX 77058, Department of Chemistry, Fordham University, 441 East Fordham Road, Bronx, NY 10458, Carl Sagan Center, SETI Institute, 515 North Whisman Road, Mountain View, CA 94043, Department of Physics, Unive...

Introduction: Primitive achondrites are meteorites with near-chondritic bulk compositions and nonchondritic textures [1]. They are thought to be either highly metamorphosed chondrites, or residues formed by low degrees of partial melting [1]. They thus record the conditions at the onset of asteroidal melting and form an important link between chondrites and the extensively melted achondrites (i...

Introduction Conclusions References

Stable isotope patterns in lichens are known to vary largely, but effects of substrate on carbon and nitrogen stable isotope signatures of lichens were previously not investigated systematically. N and C contents and stable isotope (δ(15)N, δ(13)C) patterns have been measured in 92 lichen specimens of Xanthoria parietina from southern Bavaria growing on different substrates (bark and stone). Ph...

Methane concentrations in the pore waters of Eckernförde Bay in the German Baltic Sea generally reach gas bubble saturation values within the upper meter of the sediment column. The depth at which saturation occurs is controlled by a balance between rates of methane production, consumption (oxidation), and transport. The relative importance of anaerobic methane oxidation (AMO) in controlling di...

Isotopic composition of snow cover and streamflow was determined in a snowdominated, forested watershed to quantify the spatial variability and processes that alter stable isotope (oxygen-18, 18O and deuterium, 2H) composition under different forest canopy conditions (clear-cut, partial-cut (thinned), and unimpacted forest). Snow sampling was carried out on 4 days in late winter and early sprin...

Noble gas analysis can be performed on two types of ice core samples. First, atmospheric air, trapped in bubbles in polar ice, can be extracted and analyzed for its noble gas composition. Variations in the isotopic and elemental composition of noble gases reveal changes in the composition of the paleoatmosphere or the impact of climate-related physical processes acting when the air was enclosed...