v3.2.0

IGM 3.2.0 — Full list of changes

Release: 3.2.0 -> 3.1.2

Breaking changes (require action — see migration guide)

• Environment: TF ≥ 2.16 / Keras ≥ 3.12 required; Keras-2 env fails at first ice-flow solve.
• Default stack: the iceflow emulator used to run pretrained under the emulated mode;
  it now runs under the unified mode, trained from scratch with the dahunet
  architecture by default, as this proved to be a much more robust choice. The default
  number of vertical layers numerics.Nz also dropped 10 → 4.
• Friction rename: slidingco → tau_ref on the unified mode
  (legacy stack keeps slidingco); hard-fail at startup naming each key.
• Physics parameters renamed and regrouped: the iceflow.physics parameters were
  reorganised under two blocks — sliding: (per-law sub-blocks flattened one level up)
  and viscosity: (Glen-flow parameters) — with init_ prefixes dropped and a few keys
  renamed for consistency. Old keys hard-fail at startup naming their replacement. (Full
  translation table in the migration guide.)
• data_assimilation moved processes → assimilations: the data_assimilation
  module now lives in the new assimilations module category (alongside the new, fully
  rewritten field_inversion), no longer under processes.
• smb / climate umbrella modules: the individual smb_simple / clim_* modules
  are replaced by umbrella smb / climate modules with a method: selector.
• enthalpy decoupling: pieces formerly bundled in enthalpy are now standalone —
  arrhenius split into its own process, and subglacial hydrology / effective pressure
  moved to subglacial_hydrology. The former vert_flow module was folded into
  iceflow, which now optionally computes the vertical velocity (e.g. required to run
  enthalpy or particles).

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Changes by module

• subglacial_hydrology (new):

  • Decoupled from enthalpy; computes state.effective_pressure for Budd and Coulomb sliding
  • Modes: constant_one, percentage, ocean_connected, from_input, till_storage

• arrhenius (new):

  • Decoupled from enthalpy into a standalone process module

• iceflow:

  • New: unified stack — trains a from-scratch dahunet emulator online,
    now the default ice-flow method
  • New: Several sliding laws, including budd, regu_coulomb, mohr_coulomb.
  • New: pretrained dahunet emulators (full, mini, micro) shipped with IGM;
    referenceable by name (e.g. pretrained_path: dahunet)
  • Renaming: slidingco → tau_ref (legacy alias kept for backward compatibility)
  • Defaults: sliding.u_ref 1 → 100 m/yr (unified only; legacy emulated/solved/diagnostic
    require u_ref=1.0, enforced at startup), with sliding.tau_ref rescaled 0.0464 → 0.215
    so the physics is unchanged
  • Config: viscosity parameters regrouped under viscosity: block; sliding sub-blocks
    flattened; init_ prefix dropped on friction keys
  • Numerics: choice of bx/by discretisation; extra 2nd-derivative regularisation term
  • Floating: updated to use 2D water_level for calving-front basal pressure
  • New: iceflow.vertical_velocity folds in the former vert_flow process

• enthalpy:

  • Simplified diagnostics; T and omega no longer saved by default
  • New: temppasurf and temppabase published on state
  • arrhenius and subglacial hydrology split out into standalone modules

• data_assimilation (moved to assimilations):

  • Moved from processes to the new assimilations category
  • Updated to accept either slidingco or tau_ref as friction control
  • Regularization: additional second-order term in regu_thk; configurable
    discretization for bx/by (PR #45)
  • Default params changed: retrain_iceflow_model false, fix_opti_normalization_issue
    true, obstacle_constraint: [reproject], smooth_anisotropy_factor 1.0,
    convexity_weight 0.0
  • (Superseded by field_inversion — see below)

• smb / climate (new):

  • Umbrella modules introduced with method: dispatch to smb_* / clim_* submodules
    (simple/oggm/accpdd; simple/oggm/glacialindex/station)

• field_inversion (in assimilations):

  • Overhauled data assimilation — alternates inversion with light retraining

• pretraining (in assimilations):

  • Moved from processes to new assimilations category
  • Model artifacts migrated to .keras format (manifest removed)
  • Pretrained network validated against config on load (horizontal + vertical basis checks)
  • New SIADecompNet architecture

• time_relaxation (in assimilations):

  • New module (alternative to field_inversion) that permit data assimilation
    but using time relaxation.

• time:

  • New: cfl_percentile option for adaptive time-stepping

• state:

  • New: variable aliases
  • New: diagnostic variables are now optional (opt-in)

• core:

  • New: check_module_needs flag to validate module dependencies at init (off by default)

Code maintenance

• Black formatting enforced in CI
• Hewitt & Schoof (2017) subglacial hydrology benchmark test added

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Contributors: @shrrosier, @jouvetg, @tgregov, @gillian-smith.