README
======

PolarLakes

This dataset provides bi-weekly supraglacial lake extents for 22 Antarctic ice shelves.

For a detailed description of the dataset, please refer to: 
Baumhoer, C. A., Koehler, J., Wouters, B., Lhermitte, S., Dietz, A. J., and Kuenzer, C.: PolarLakes: A Bi-Weekly Dataset of Supraglacial Lakes on Antarctic Ice Shelves from Multi-Sensor Satellite Observations (2015-2024), Earth System Science Data Discussions, 1–24, https://doi.org/10.5194/essd-2025-569, 2026.


Dataset description
--------------------

This dataset contains bi-weekly and annual mosaics of supraglacial lake
extent, derived per ice shelf ("shelfname"). All raster files are provided
in coordinate reference system EPSG:3031 (Antarctic Polar Stereographic)
with a pixel size of 10 m.

Folder and file structure
--------------------------

<shelfname>/
    Top-level folder named after the ice shelf. Contains the three
    subfolders described below.

    <shelfname>_biweekly_mosaics/
        Binary rasters of bi-weekly maximum lake extent.

        File naming: yyyy-mm-01_max_extent.tif / yyyy-mm-02_max_extent.tif
            yyyy  - year
            mm    - month
            01    - first half of the month (days 1-15)
            02    - second half of the month (day 16 to end of month)

        Pixel values:
            0 = no lake / not classified as ponded water
            1 = maximum lake extent detected in this bi-weekly period

    <shelfname>_biweekly_contribution_mosaics/
        Same spatial and temporal structure as
        <shelfname>_biweekly_mosaics, but pixel values indicate which
        satellite sensor(s) contributed to the classification, rather
        than a binary lake/no-lake mask.

        File naming: yyyy-mm-01_max_extent.tif / yyyy-mm-02_max_extent.tif
            (same convention as above)

        Pixel values:
            1 = classified using Sentinel-1 only
            2 = classified using Sentinel-2 only
            3 = classified using Sentinel-1 and Sentinel-2 

    <shelfname>_annual_mosaics/
        Annual rasters summarizing the bi-weekly frequency of surface
        ponding during the melt season (November-March).

        Each melt season contains at most 12 bi-weekly periods
        (12 x ~2 weeks spans November 1 to March 31), so one bi-weekly
        detection of ponding equals a count of 1.

        Two file types are provided per melt season:

        sum_<startyear>-11-01_<endyear>-03-31_<shelfname>.tif
            Per-pixel sum of bi-weekly ponding detections over the melt
            season indicated by the dates in the file name (November 1
            of <startyear> through March 31 of <endyear>). Values range
            from 0 (never ponded) up to a maximum of 12.

        total_<startyear>-11-01_<endyear>-03-31_<shelfname>.tif
            Per-pixel bi-weekly frequency of ponding, i.e. the number of
            bi-weekly observation periods available/used for that pixel
            over the same melt season. Because the observation time
            frame differs between shelves (see dates in file name), the
            maximum possible value varies from shelf to shelf.

For questions contact: celia.baumhoer@dlr.de