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FRINATEK-Fri mat.,naturv.,tek

Isotopic Transfer Rates During Water Phase Changes

Alternative title: Isotopiske overføringsforhold ved vannfaseendringer

Awarded: NOK 12.0 mill.

What if we could look directly into the processes governing the atmospheric water vapor, what would we see? The iTRANSFER project will allow us to do this accurately. Water is not just water. Water consists of different types of water molecules where some of the molecules are heavier than others due to the number neutrons. We can with the help of advanced laser instruments measure the relative composition of heavy and light water molecules in liquid, ice, and vapor. As the heavy and light water molecules are behaving slightly differently when going from one phase to another, for example when the water evaporate, or when the vapor forms snow crystals, we can use measurements directly in the atmosphere of the different types of water to understand the processes of the hydrological cycle. However, to be able to interpret our observations from nature we need to know the governing laws under ideal conditions when just one parameter is varied at a time. iTRANSFER will with extreme precision describe how the temperature and humidity gradients influence the phase change transfer rate of the different types of water molecules. What makes iTRANSFER special is the planned use of ultra-precise laser instruments. With state-of-the-art measurement capabilities at hand, iTRANSFER will now be able to carry out experiments using setups allowing measurements to be conducted on extremely small samples at unprecedented high temporal resolution. The research carried out as part of iTRANSFER will not only support our understanding of the water cycle on Earth, but will also form the basis for understanding the water cycle on Mars and on the Moon. Future measurements of water samples found on Mars and the Moon can potentially with the research from iTRANSFER inform us about the past evolution of the surface of these extraterrestrial objects and lead to a better understanding of how the Earth was formed.

Water stable isotopologues in an air mass carry an integrative fingerprint of the ambient conditions due to the different molecular structures causing fractionation during phase change. This makes the water isotopic composition an important and useful proxy for quantifying the physical processes of the hydrological cycle on the Earth. The basis for research using water isotopologues is the equilibrium and kinetic fractionation factors during phase changes. Mounting experimental results and environmental observations have raised questions to the validity of our nearly half a centennial old description of isotopic equilibrium and kinetic fractionation factors describing the water isotopologue transfer rates during phase changes between solid, liquid, and vapor. This uncertainty in the formulations creates an ambiguous foundation on which the geoscientific community relies upon for providing understanding of the climate and environmental systems. This proposal consists of an experimental and modeling component that will establish an accurate basis for use of water isotopologues in studies of the terrestrial hydrological cycle by making accurate measurements of the equilibrium and kinetic fractionation factor. The project will operate based on the following three hypotheses addressed in separate work packages (WP): Hypothesis 1: Equilibrium fractionation factors for water isotopologues are not accurately determined for phase changes below 0°C (WP 1). Hypothesis 2: Kinetic fractionation factors for water isotopologues during evaporation are not accurate determined (WP 2). Hypothesis 3: More accurate fractionation factors will lead to better simulation in climate models of the water isotopologues in the atmosphere (WP 3).

Funding scheme:

FRINATEK-Fri mat.,naturv.,tek