Introducing ELSA: An isochronal model for ice sheet layer-age tracing

We are presenting the ice-sheet layer-age tracer ELSA (Englacial Layer Simulation Architecture) — a model that uses a straightforward method to simulate the englacial stratification of large ice sheets — as an alternative to Eulerian or Lagrangian tracer schemes. ELSA’s vertical axis is time; individual layers of accumulation are modeled explicitly and are isochronal.  ELSA is not a stand-alone ice-sheet model, but requires uni-directional coupling to another model providing ice physics and dynamics (the “host model”). Via ELSA’s layer tracing, the host model’s output can be evaluated throughout the ice sheet interior using ice core or radiostratigraphy data.  We show results regarding the stability and resolution-dependence of this coupled modeling system using simulations of the last glacial cycle of the Greenland ice sheet with Yelmo as the host model. We present options for making ELSA computationally efficient enough for ensemble runs, as well as requirements for offline forcing of ELSA with output from a range of existing ice-sheet models.  ELSA is an open source project and available on git (https://git.app.uib.no/melt-team-bergen/elsa) for the ice sheet modeling community.