Extreme seasonal changes in light conditions are among the key characteristics of high Arctic ecosystems with far-reaching implications for their potential to generate biomass via photosynthetic primary production. As a result, Arctic ecosystems are usually characterized by a very short productive period during spring/summer that provides the entire annual biomass production available for higher trophic levels. Of particular ecological importance is the bottom ice algae bloom, which provides a pulse of primary production when no other significant food source exists in the marine ecosystem. Solar angle, sea ice cover and snow thickness are the main factors that determine timing and progression of the bottom ice algae bloom, while nutrient availability often affects the peak magnitude (and nutritional quality) of algal blooms. In this work, we summarize a pan-Arctic dataset of bottom ice algae biomass time series to describe latitudinal gradients in bloom development and the processes that control these gradients. We conclude with a discussion of potential implications for ecosystem structure and trophic fate of the produced biomass. The ongoing changes due to climate warming lead to alterations of environmental conditions, and their consequences for Arctic productivity are still heavily debated. By comparing pan-Arctic data on the seasonal development of vernal bloom processes and different bloom scenarios, we try to identify the most important factors determining the phenology of bottom ice algae during this important transitional phase in the Arctic.