The connected isotopic water cycle in the Community Earth System Model Version 1

In a transient Last Millennium simulation covering the 850–2005 period, iCESM1 correctly captures the late-twentieth-century structure of δ18O and δD over the global oceans, with more limited accuracy over land. The relationship between salinity and seawater δ18O is also well represented over the observational period, including interbasin variations. We illustrate the utility of coupled, isotope-enabled simulations using both Last Millennium simulations and freshwater hosing experiments with iCESM1.

Closing the isotopic mass balance between all components of the coupled model provides new confidence in the underlying depiction of the water cycle in CESM, while also highlighting areas where the underlying hydrologic balance can be improved. The iCESM1 is poised to be a vital community resource for ongoing model development with both modern and paleoclimate applications.