Saisonale Variation von Deuterium und Sauerstoff-18 in Luftfeuchte und Niederschlag über Antarktika

Abstract

D and (18)O distributions were investigated in Antarctic precipitation (falling snow) and in water vapour to study their dependance on season and sampling site. Long-term sampling at the former German Georg Forster Station during 1978-93 and at the Japanese Syowa Station during 1994-97 allow conclusions about the present seasonal isotopic variations in the water inflow to Antarctica. The δD and δ(18)O values of precipitation at these East Antarctic coastal stations were compared with corresponding data from the West Antarctic Georg von Neumayer and Halley stations. The monthly means of these long-term data sets show typical hysteresis-like seasonal patterns of isotopic composition. Significant time lags exist regarding station temperatures, while water vapour δD values do not show such hysteresis patterns. Here, half-yearly and even quarter-yearly time components were found by Fourier analysis. Attempts were made to describe the variation in δD and δ(18)O values of water vapour and precipitation as well as in the resulting deuterium excess by the mixed cloud isotopic model (MCIM) of Ciais and Jouzel.

Isotopic exchange on the diurnal scale between near-surface snow and lower atmospheric water vapor at Kohnen station, East Antarctica

“…It is generally assumed that no fractionation occurs during sublimation. Using Greenland data, Steen-Larsen et al (2011) and Landais et al (2012) showed that on average the snow surface isotopes and the water vapor isotopes are in equilibrium, and they estimated that the value of the equilibrium factor lies between the fractionation coefficient α ice with respect to ice (Merlivat and Nief, 1967;Ellehoj et al, 2013) and the fractionation coefficient α water with respect to water (Majoube, 1971). In this study, we test different hypotheses to obtain a range of prediction of the isotopic variation in the vapor and the snow surface.…”

“…These analyzers are able to perform continuous and in situ measurements of the humidity mixing ratio (defined as the mass of water vapor divided by the mass of dry air) and the stable water vapor isotope concentrations. Prior to this advance, water vapor could only be collected using tedious cold trapping methods (e.g., Jacob and Sonntag, 1991;Steen-Larsen et al, 2011;Angert et al, 2008), deployed until sufficient amounts were collected to allow subsequent transfer to vials and later mass spectrometer analyses. Such a task was almost impossible to perform routinely (e.g., Schwarz et al, 1998).…”