# Antarctic Drainage Basin Delineation (ESRI Shapefile, GeoJSON, GeoPackage)

This repository contains two versions of Antarctic drainage basin delineations per geometry file format (ESRI Shapefile, GeoJson, GeoPackage)

The drainage divides of ice sheets separate the overall glaciated area into multiple sectors. These drainage basins are essential for partitioning mass changes of the ice sheet, as they specify the area over which basin specific measurements are integrated. In [(Krieger et al., 2020)](https://doi.org/10.1016/j.rse.2019.111483) we developed a modified watershed algorithm for delineating individual glaciers and applied it to the Northeast Greenland sector. Here we extended the processing to the entire Antarctic Ice Sheet.

Individual glacier catchments support a quantification of glacier changes for a specified region and are therefore an important tool in the field of glaciology and hydrology. The Antarctic drainage basins provide detailed information for partitioning mass changes of the ice sheet to the individual glacier or regional level.

In the modified watershed approach ice sheet wide velocity measurements by Sentinel-1 SAR [(Nagler et al., 2015)](https://doi.org/10.3390/rs70709371) and the 90 m TanDEM-X Polar DEM [(Wessel et al., 2021)](https://doi.org/10.5194/tc-15-5241-2021) are combined to derive individual glacier drainage basins for the entire Antarctic Ice Sheet. The algorithm is seeded at the grounding line [(Mouginot et al., 2017)](https://doi.org/10.5067/AXE4121732AD)


Originating from selected seed points at the grounding line we produced discrete stream lines based on the methodology of [(Cabral et al., 1993)](https://www.osti.gov/biblio/10185520) for all areas exceeding a threshold of 50 m/yr and followed these upstream. For slower areas a classical flood-filling watershed algorithm is adopted [(Beucher et al., 1992)](https://digitalcommons.usu.edu/microscopy/vol1992/iss6/28). A Monte Carlo simulation was performed, repeating the catchment delineation procedure 5000 times to account for uncertainties. The final catchment label was then determined by selecting the label that emerged as the majority outcome across all simulations. For processing details please consult [(Krieger et al., 2020)](https://doi.org/10.1016/j.rse.2019.111483).

The methodology has been validated in the Northeast Greenland sector by comparing the basin extent to existing delineations in the literature. Marginal discrepancies in catchment area arise for various reasons, including the choice of the DEM, the velocity dataset or the used methodology. As an independent, high accuracy data base for full validation of the results is lacking, quality assessment was supported by performing an intercomparsion with different input data combinations of DEMs and ice velocity products showing discrepancies of up to 16% in the extent of the catchment area. The quality of the presented results was further assessed by a probability measure from additional Monte-Carlo experiment.

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## Files Included

The geometries are provided in 3 different filetypes:
- **`shp`:** ESRI Shapefile (provided as tarball)
- **`geojson`:** GeoJSON
- **`gpkg`:** GeoPackage

### `antarctic_basins`

This shapefile provides polygon features representing each **major drainage basin** of Antarctica.

Although outlet glaciers of Greenland are typically located in narrow fjords, the **lateral separation** of Antarctic catchments is often **less clearly demarcated** and so we choose to keep the separation already performed for **past catchment delineation** by  [(Mouginot et al., 2017)](https://doi.org/10.5067/AXE4121732AD)

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### `antarctic_basins_10km`

This shapefile introduces a **finer spatial subdivision** of the major drainage basins defined above. Polygons in this dataset are derived by subdividing each major catchment at **regular 10 km intervals along the grounding line**.

> **Important note:**  
> We intentionally avoid referring to these subdivisions as independent *drainage basins* or *catchments*. They are **not** meant to be analyzed in isolation.

Instead, this dataset is best understood as a **collection of drainage units nested within each major basin**, which may be useful in analyses such as mass budget assessments by increasing the **spatial resolution** over which Antarctic-wide measurements can be aggregated. By working within the boundaries of a single major catchment, researchers can take advantage of this subdivision while preserving the overall hydrological integrity of the system.

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## Citation

If using these shapefiles in academic or research contexts, please cite:

> Krieger, L., Floricioiu, D., & Neckel, N. (2020).  
> *Drainage basin delineation for outlet glaciers of Northeast Greenland based on Sentinel-1 ice velocities and TanDEM-X elevations.*  
> Remote Sensing of Environment, 237, 111483.  
> https://doi.org/10.1016/j.rse.2019.111483

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## License

CC BY 4.0

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## Contact

For questions or feedback, please contact:  
Lukas Krieger 
lukas.krieger@dlr.de