Brief communication: An active subglacial lake beneath the upper Institute Ice Stream, West Antarctica, missing from existing inventories

We report an active subglacial lake beneath the upper Institute Ice Stream, West Antarctica (82.21° S, 68.85° W) absent from published inventories; the nearest catalogued lake is 70 km away. ICESat-2 laser altimetry and stereo elevation models independently record surface uplift of up to 5.9 m between 2012 and 2021 (+0.13 ± 0.03 km3), a fall of 8.7 ± 0.5 m at the centre of a 45 km2 outline between late 2021 and mid-2023 (−0.17 ± 0.02 km3), and slow recharge since. Two bed compilations route overflow 54–64 km north-north-east to the grounding line. Radar confirmation is still needed.