Isotopic Curve (IMAGE) University of Copenhagen - Niels Bohr Institute Caption The curve at the isotopic composition of the water vapour between the snow surface and a height of 40 m shows that at a height of 2-4 meters there is a minimum of 18O. So there is a boundary layer that separates the lower layer and the upper layer in the atmosphere. Credit (Credit: Berkelhammer et al.) Usage Restrictions (Credit: Berkelhammer et al.) License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.