---
title: "Iceland Glacier Projections — Delivery Overview"
subtitle: "OGGM hindcast and CMIP5/CMIP6 projections for Landsvirkjun"
author: "Fabien Maussion & Patrick Schmitt"
date: 2026-07-07
format:
  html:
    output-file: delivery_overview.html
    toc: true
    embed-resources: true
---

## What this is

This delivery contains state-of-the-art OGGM hindcast and future projections for all
572 Icelandic glaciers, run to 2100 and 2300 under the CMIP5 and CMIP6 climate model
ensembles, together with the notebooks used to select, validate, and analyse them.
The projections are intended to support your team's work on how projected changes in
the Atlantic Meridional Overturning Circulation (AMOC) may influence Icelandic glacier
evolution — see `Landsvirkjun consultancy` (google doc) for the original scope of
this work.

## Configuration used

Two climate forcings were calibrated and validated: **CARRA** and **ERA5** (1991-2026).
**CARRA (trapezoidal bed shape, lambda=14) is the delivered configuration** used
throughout the main projections. **ERA5 (lambda=8) was selected as the best-performing
configuration for this climate forcing** and is kept
alongside it for comparison — the two configurations differ only modestly in their
projected volume loss. The full reasoning and validation evidence behind this choice is
in notebook `00`, below.

## Contents & how to read this delivery

Each notebook below is linked two ways: an **nbviewer** link (read directly in your
browser, no setup needed) and the underlying **.py script** (a plain, `# %%`-commented
Python file — the notebook `.ipynb` next to it was generated from this script and is
the exact same content, just executed). Either can be opened directly in Jupyter if you
want to re-run or adapt the analysis.

1. **[00 — Experiment selection & validation](https://nbviewer.org/urls/cluster.klima.uni-bremen.de/~fmaussion/share/iceland_projections/00_experiment_selection_and_validation.ipynb)**
   ([.py script](https://cluster.klima.uni-bremen.de/~fmaussion/share/iceland_projections/00_experiment_selection_and_validation.py)) —
   the calibration sweep (climate forcing × bed shape × mass-balance model) validated
   against glacier area, Hugonnet mass change, DEM-differenced volume change, and SMB
   maps, ending in the decision to ship CARRA, lambda=14.

2. **[01 — Comparison with reference models](https://nbviewer.org/urls/cluster.klima.uni-bremen.de/~fmaussion/share/iceland_projections/01_model_comparison.ipynb)**
   ([.py script](https://cluster.klima.uni-bremen.de/~fmaussion/share/iceland_projections/01_model_comparison.py)) —
   how our Iceland-specific calibration compares to three independent published
   projections (OGGM standard, GloGEM, PyGEM-OGGM) for the same glaciers.

3. **[02 — Projections analysis](https://nbviewer.org/urls/cluster.klima.uni-bremen.de/~fmaussion/share/iceland_projections/02_projections_analysis.ipynb)**
   ([.py script](https://cluster.klima.uni-bremen.de/~fmaussion/share/iceland_projections/02_projections_analysis.py)) —
   **the main deliverable.** Total Iceland glacier volume to 2100 and 2300, the same
   projections re-grouped by global temperature level and by AMOC index, and total
   glacier runoff by AMOC index (following the same method as the
   [OGGM-EDU tutorial on glacier water resources](https://edu-notebooks.oggm.org/oggm-edu/glacier_water_resources_projections.html)).
   This is the notebook to start from if you want an initial analysis of the
   projections themselves, or a template to build your own.

4. **[03 — AMOC index](https://cluster.klima.uni-bremen.de/~fmaussion/share/iceland_projections/03_amoc_index/)**
   — two standalone CLI scripts (`amoc_index_timeseries.py`, `amoc_index_classify.py`,
   not notebooks) that build the AMOC-strength classification used in notebook `02`,
   plus `amoc_index_table_README.txt` documenting the full methodology and the
   already-computed output tables. See *Data* below for what is and isn't shipped here.

## Downloading this delivery

Everything in this README — notebooks, scripts, figures, and data — is hosted at:

<https://cluster.klima.uni-bremen.de/~fmaussion/share/iceland_projections/>

You can browse it directly in a browser, or download the whole delivery as a single
archive:

<https://cluster.klima.uni-bremen.de/~fmaussion/share/iceland_projections.tar.gz>

```bash
wget https://cluster.klima.uni-bremen.de/~fmaussion/share/iceland_projections.tar.gz
tar -xzf iceland_projections.tar.gz
```

The archive is about 4.1 GB (compressed).

## Key results

![Total Iceland glacier volume, 2000-2100, by scenario (notebook 02)](figures/volume_projections_2100.png)

![Total Iceland glacier volume, 2000-2100, grouped by AMOC index (notebook 02)](figures/volume_projections_amoc_index.png)

![Total Iceland glacier runoff, grouped by AMOC index — note the "peak water" divergence between groups (notebook 02)](figures/runoff_projections_amoc_index.png)

![Comparison with published reference models, CMIP6 (notebook 01)](figures/volume_model_comparison_cmip6.png)

![Historical mass change vs Hugonnet et al. observations, shortlisted configurations (notebook 00)](figures/validation_mass_change.png)

More figures are in the `figures/` folder, and each notebook produces the ones
relevant to its own analysis.

## Data

All data referenced by these notebooks ships alongside them, organised under `data/`:

```
data/
  historical/     — CARRA and ERA5 historical OGGM runs (1991-2026)
  projections/    — merged CMIP5/CMIP6 projection NetCDFs (2100 and 2300), CARRA only
  supporting/     — observations (Hugonnet, SMB maps), reference-model CSVs,
                    global-temperature-level tables, and the AMOC index's own
                    supporting files (subpolar-gyre mask, Weijer et al. streamfunction)
```

Two things are **not** shipped, to keep this delivery a manageable size:

- **The full calibration sweep** behind notebook `00` (~15 configurations across bed
  shape and mass-balance model choices) — only the shortlisted configurations' data is
  included. The full sweep's data can be made available on request.
- **The raw CMIP6/CMIP5 GCM `tas` files** used by `amoc_index_timeseries.py` to build
  the AMOC index from scratch (73+ files, too large for this delivery). The
  already-computed output (`i_tas_timeseries.csv`, `amoc_index_table.csv`) is included,
  so `amoc_index_classify.py` and notebook `02` run standalone. To regenerate the index
  from scratch, the GCM files are publicly available at:
  - CMIP6: <https://cluster.klima.uni-bremen.de/~oggm/cmip6/>
  - CMIP5: <https://cluster.klima.uni-bremen.de/~oggm/cmip5-ng/>

## Running this delivery

The notebooks use only relative paths (`data/`, `figures/`, `../03_amoc_index/`), so
they must be run from within this folder. A standard scientific Python environment is
enough: `xarray`, `pandas`, `numpy`, `matplotlib`, `pyyaml`, and `jupytext` if you want
to convert the `.py` scripts back to notebooks yourself
(`jupytext --to notebook 02_projections_analysis.py`). The AMOC index scripts
additionally need `regionmask`, `scipy`, and `cf_xarray`/`xesmf`-adjacent packages only
if re-run from raw GCM data.

## About this delivery

These notebooks and scripts were built with the assistance of Claude (Anthropic's AI
coding assistant), under our direction and review. If your team wants to extend this
analysis — different scenario groupings, per-ice-cap breakdowns, other hydro variables
(melt vs. precipitation split, peak-water timing per ice cap), or anything else the
underlying NetCDF data supports — Claude Code can be pointed at this project directory
to pick up the analysis directly; the notebooks and this README are written to give it
(and any future collaborator, human or otherwise) enough context to continue from here.
