Water isotopes in the GISS ModelE land surface scheme

We describe the isotope-capable Land Surface Model (LSM) developed at NASA Goddard Institute for Space Studies (GISS). This model is a part of the GISS ModelE General Circulation Model (GCM), which includes the water isotopes H218O and HDO as tracers in every aspect of the modelʹs hydrological cycle. We discuss results for the soil isotopes from a number of full GCM simulations. In particular, we focus upon the spin up and equilibrium behavior of the isotope fields in a present day (ca. 1980) control simulation and the response of the isotopes to forcings over transient AMIP-style 20th century simulations. In addition, we investigate whether the isotope fields are affected by a change in the runoff algorithm, and so examine whether the isotope fields have the potential to constrain model land surface physics.