Dataset includes 2 sets of data on Streptophyte glacier algal photophysiology as assessed through Pulse Amplitude Modulation (PAM) fluorometry of communities sampled from the surface of the Greenland Ice Sheet during summer 2024. The first set of responses are of communities sampled from fully exposed versus shaded regions of ice measured through rapid light curve techniques after 5 minutes of dark adaptation. The other set of responses are the same surface ice samples measured after 24 hours of dark-adaptation and melt. Analysis of rapid light curve datasets to highlight fine-scale heterogeneity in glacier algal in-situ photophysiology are published in Williamson et al. (2024). This marks the first time an in-situ method has been developed to map glacier algal photophysiology relative to dominant abiotic stressors. Funding provided by the following: Leverhulme Trust "iDAPT" project RPG2020-199 National Environmental Research Council "CASP-ICE" project NE/Y002636/1 ERC Synergy "Deep Purple" project 856416

The abundance, photophysiology, pigmentation, bio-optical properties, cellular energy balance and instantaneous radiative forcing of glacier algal assemblages from the surface of the Greenland Ice Sheet (GrIS) are quantified throughout the 2016 ablation season. The effects of assemblages on ice surface albedo are further derived using a newly developed model of glacier algal blooms for the GrIS, radiative transfer modelling using BioSNICAR-GO, and comparisons to MODIS broadband albedo observations over the same season. Data represent a composite of in-situ observations, in-situ incubations studies, laboratory analyses, modelling and remote sensing. All in -situ work was performed at site S6 of the K-Transect in the southwestern GrIS ablation zone as part of the Black and Bloom project. Funding was provided by the NERC ''Black and Bloom'' grant NE/M021025/1 and the Marie Sklodowska-Curie grant agreement No 675546.