Progress and Challenges in Coupled Ice-Sheet/Climate Modeling with CESM
Abstract:Bidirectional coupling of ice sheet models and climate models opens the door to research of ice-sheet/climate interaction at a global scale. However, difficulties encountered in achieving this coupling have proven non-trivial and include both:
1) Technical challenges. Ocean and atmosphere model components cannot easily handle dynamic boundaries; land surface model components cannot easily simulate exposed glacial ice, firn evolution, or evolving land surfaces; coupling infrastructure cannot easily accept new earth system components; and ice sheet models typically operate at an order of magnitude higher spatial resolution than climate models and on regional domains, and require very long integrations to reach an equilibrium state.
2) Scientific challenges. The glaciological modeling and climate modeling communities often work on topics that cover very different spatiotemporal scales; carry out research using very different models and with very different modeling paradigms; and do not consider coupled ice-sheet/climate behavior across the various ice-sheet/climate physical interfaces.
These technical and scientific challenges are being tackled within the Community Earth System Model. The resulting coupled architecture (“CESM-CISM”) is now capable of simulating the Greenland ice sheet (GrIS) in the climate system. The model includes a relatively sophisticated representation of surface mass balance (SMB), explicit resolution of important ice-sheet climate communication pathways, and prognostic ice dynamics. First results, underpinned by modelled SMB validation, have explored changes in GrIS mean SMB and its variability, partially-coupled GrIS evolution, and emergence of an anthropogenic signal in SMB under RCP8.5 climate forcing. Ongoing work with the evolving CESM-CISM will set the stage for fully-coupled simulations of Greenland in past and future climates, and also for potential integration of the Antarctic ice sheet into a true coupled modeling framework.