Master 2 internship, Corentin Le Yhuelic, supervised by Mathieu Casado
The water isotopes have different behaviours during each transformation throughout the hydrological cycle, the water vapor that travels from the ocean to the Antarctic plateau is depleted in heavy isotopes at each phase transition. Therefore, we can understand different parameter on the climate as when the climate is warmer there is more precipitation which leads to a bigger depletion in heavy isotopes, while a colder climate leads to a dryer climate, with less precipitation and so more heavy isotopes in the ice-core. Thus, in order to understand the climate that led to the values measured in an ice-core, we need to better characterize fractionation.
The fractionation has already been conducted by Merlivat and Nief for αD [Merlivat-Nief1967], Majoube for α18 [Majoube1971], and more than 40 years later in 2013 by Ellehoj for both coefficient [Ellehoj2013]. However, the measurements diverge especially at low temperature.
Thus, it is necessary to better understand how the snow is forming on the surface. Currently there are 2 hypothesis that need to be investigated: either there is a different probability for each isotope to condensate on the surface (H1), or the water molecule is always condensing, but there is a different probability for each isotope to get detached by the surrounding gas molecules (H2). The aim of the internship is to use a brand-new spectroscopy device and a set-up well controlled in order to measure the fractionation coefficient, and understand better condensation.
