siim — Sliding Ice Incision Model

Coupled glacial–fluvial landscape evolution. siim couples a sliding-ice incision law to fluvial stream-power erosion on a common grid, so one model grows mountains, carves glacial troughs, and relaxes them fluvially as the climate forcing moves the equilibrium-line altitude (ELA) up and down.

Three front ends share one set of physics and constants (siim.constants):

• 1D profile model (siim.siim1d) — a single glacial–fluvial long profile; fast and standalone.

• 2D landscape model (siim.siim2d) — a raster model (single-flow or D-infinity routing, sub-grid glacier-width carving), with a rifted-margin escarpment variant in siim.escarpment. Its default mode-C standard combines bed memory, width carving, and trunk-surface routing. Since 0.9.1 it runs standalone on a plain pip install (in-house time loop, routing, flexure, and diffusion).

• Analytical steady state (siim.analytical) — one closure engine behind three front ends (GeneralProfile, MarginalCoulombProfile, SteadyStateProfile), plus a nondimensional regime map (siim.analytical.regime) for the bistability boundary. Both numerical models embed it as their reference. numpy/scipy only.

siim’s glacial physics is also available as an optional fastscape adapter (siim.fastscape), for composing the physics into your own fastscape/xsimlab model — see Use siim’s glacial processes in your own fastscape model. It needs the fastscape stack (pip install siim-lem[fastscape], conda for the Fortran backend); the standalone 2D model above does not.

The governing equations are documented in a model description paper in preparation. The code uses the channel-floor convention zs = zb + 1.5*H (see Concepts).

To get started, install siim (Installation), then run the 1D walkthrough (Your first 1D run). Concepts describes the state conventions (modes, the channel-floor datum, sub-grid width); the parameters that set the regime are explained in Configuring a run, with every numerical-model key in Numerical-model parameter reference, and the glacial ones interpreted in Choosing glacial parameters.

Get started

• Installation
  • Standard install
  • Numba threading
  • Optional: the fastscape adapter (conda)
• Your first 1D run
• Your first 2D run

Guides

• Concepts
  • What the state is: mode A, B, and C
  • The channel-floor datum: where the bed sits
  • Sub-grid width: one glacier, many cells
• Configuring a run
  • Surface-evolution mode — mode
  • Sub-grid glacier-width carving — carve_width (2D)
  • The mode-C standard (carved runs)
  • Sliding law — sliding_law
  • Flow routing (2D) — flow_routing
  • Climate and uplift forcing
  • Base level and the coastline — bl
• Numerical-model parameter reference
  • Parameters accepted by both models
  • 1D-only parameters
  • 2D-only parameters
  • Initial-topography formats
  • Running the 2D model through the optional adapter
  • Escarpment-variant additions
• Choosing glacial parameters
  • The mass-balance gradient beta and the lapse rate
  • The erosion coefficient ce and slope exponent nu
  • The power-law sliding length lambda_p
  • The Coulomb sliding length lambda_c
• Outputs, plotting, and saved runs
  • Plotting
  • Smooth and raw landscape views
  • 1D arrays
  • 2D dataset and arrays
  • The true-state output convention
  • Files and output locations
  • Saving and loading a 2D run
• Use siim’s glacial processes in your own fastscape model
  • The quickest path
  • Composing into your own model
  • The processes

API reference

• API reference
  • Analytical steady state
  • 1D profile model
  • 2D landscape model
  • fastscape integration — siim.fastscape
  • Numerical core — siim._core
  • Constants and support modules

Bibliography

• References