Ubiquitous and expanding glacier algal blooms modelled around the Greenland Ice Sheet

Abstract Glacier algal blooms occupying the melting surface of the Greenland Ice Sheet (GrIS) support diverse microbial communities and amplify ice melt through positive albedo feedback. Knowledge about the distribution and magnitude of these blooms has been limited to isolated field surveys or regional remote sensing and modelling studies to-date. Here, we present Greenland-wide simulations of glacier algal blooms over the past two decades (2000–2022) using a Quasi Monte Carlo (QMC) ensemble approach informed through sensitivity analysis of key model parameters. We show how conditions conducive for glacier algal growth are present around the entirety of the GrIS margins each year of our study regardless of the magnitude and duration of the melt season. Spatiotemporal heterogeneity in accumulated biomass is modelled across the ablation zone, between ice sheet sectors and relative to inter-annual variability in melt. Bloom magnitude maps to the availability of ablation zone area in each year and we identify northern sectors as potential harbingers of expansive blooms that remain to be sampled. A small increasing trend in total bloom extent (3724 km −2 yr −1 ) between 2000 and 2022 supports the likelihood of future bloom expansion as more of the ice sheet is unlocked by warming.