Date: 09.02.2026
Green ice on Lipno Reservoir visible from space, confirmed by Copernicus Satellite Imagery
At the beginning of January this year, the Biology Centre of the Czech Academy of Sciences reported the documentation of an unusual phenomenon at the Lipno Reservoir — the occurrence of so-called green ice, caused by a high concentration of cyanobacteria. This phenomenon has now been confirmed by satellite imagery from the European Copernicus programme.
Images acquired on 18 December 2025 by one of the Copernicus Sentinel-2 satellites show the frozen surface of the Lipno Reservoir with a distinct green coloration of the ice, particularly visible in the central part of the reservoir. While the north-western section displays ice in typical pale whitish tones without the presence of cyanobacteria, the central area clearly shows frozen water containing cyanobacterial biomass. In the south-eastern part of the reservoir, the water remained unfrozen, and the satellite imagery also captured an active algal bloom extending along the narrow basin of the reservoir.
The green ice formed as a result of the accumulation of cyanobacteria in the water column, which became “trapped” in the ice as the surface froze. This phenomenon is relatively rare during winter, and its extent at Lipno is exceptional even on a European scale. It demonstrates that the Lipno Reservoir is subject to long-term nutrient overload and is simultaneously influenced by climate warming, resulting in ecosystem changes occurring beyond the traditional summer season.
Data from the European Copernicus programme play a crucial role in monitoring the extent and persistence of algal and cyanobacterial blooms in water bodies. They enable long-term water-quality monitoring and provide key information for reservoir managers as well as public health authorities.
Credit: European Union, Copernicus Sentinel-2 imagery
Read also: Surprising Green Ice on Lake Lipno: Cyanobacteria Bloom in Mid-Winter
