In Greenland, where the island’s ice sheet is melting around six times faster than it was in the 1990s, billions of tons of ice are already disappearing each year. Two new studies published in January focus on the role of algal blooms and their exacerbating effect on glacier and ice sheet melt in the Arctic. The first, led by Jenine McCutcheon, a geomicrobiologist at the University of Waterloo in Canada, analyzed the biogeochemical characteristics of the dust that is deposited on ice surfaces and how it contributes to melting. In the second study, led by Beatriz Gill Olivas, a postdoctoral researcher in the Department of Environmental Science at Aarhus University in Denmark, the authors investigated whether algal growth is limited by the availability of nutrients trapped in surface ice.
Despite popular conceptions of the icy surfaces in Greenland as being white and sterile, these sites are thriving ecosystems, inhabited by a variety of algae, fungi and other microscopic organisms. Processes like aerosol deposition and deglaciation cause nutrients to accumulate on the icy surfaces, feeding algae and causing algal blooms. These algal blooms form dark, brownish-gray spots on ice sheets and glaciers that reduce albedo, the property of a surface to reflect solar radiation. Any surface with an albedo level less than 100%—essentially any surface that is not a highly reflective mirror—will absorb small amounts of heat. As a result, high albedo slows down warming and low albedo increases warming.
Raf Antwerpen, a former Ph.D. student at Lamont-Doherty Earth Observatory and current environmental data scientist, researched ice albedo modeling during his graduate studies. In an interview with GlacierHub, he explained that there are a variety of ways for excess nutrients and particulate matter to end up on glacial surfaces, causing algal blooms. Antwerpen, who did not take part in the studies, said that particles can be “deposited by wind from either distant or very local sources, such as local sediments in Greenland that are getting bigger because the ice sheet is shrinking, but also forest fires and deserts like the Sahara and the Gobi Desert. Other sources include worldwide volcanic eruptions and local infrastructure, such as transport or emissions from industrial sites.”
McCutcheon’s study samples revealed that mineral dust from local rock sources was the dominant aerosol present on the surface of the Greenland Ice Sheet. The dust comprises weathered grains containing phosphorus, a nutrient that contributes to algal blooms. Her team also estimated the potential increase in algal biomass due to nutrient delivery, theorizing that even a small amount of phosphorus can yield high levels of algal biomass. The team used the relationship between algal cell density and surface albedo to calculate an albedo value of about 0.3-0.4, which is enough to yield substantial surface melt. However, this value is likely an upper threshold for albedo reduction, as many external factors like the snowfall rate also affect aerosol deposition, and it is unlikely that algae are incorporating the full amount of the nutrient-rich dust in their growth.
Another cause of algal blooms is the transport of nutrients to the surface via ablation, the melting that removes surface ice to expose deeper ice. Through this process, the algal population is supplied with vital nutrients, particularly nitrogen and phosphorus. Gill Olivas’ team investigated whether these macronutrients are a limiting factor for algal growth and concluded that the ablation season—a summertime period of accelerated glacier melt—provides a continuous supply of nutrients to surface algae, making it unlikely that nitrogen and phosphorus are limiting. They estimated that about 212 centimeters of ablation is needed to provide sufficient phosphorus to support the algae’s growth, a smaller amount than recent ablation measurements in northern Greenland. Overall, both studies determine that rapid algal growth is darkening Greenland’s surface.
Decreased albedo leads to warmer temperatures, which will speed up the rate at which Greenland’s glaciers melt. According to Antwerpen, a major effect of glacial melt is sea level rise, which will have a “significant impact on coastal communities, ecosystems, infrastructure, anything that is in a flood plain close to a coast can just be flooded with all the consequences that you can imagine.”
Glacier melt can lead to changes to the Atlantic Meridional Overturning Circulation (AMOC), a massive system of ocean currents that circulate warm water north and cold water south, controlling climate zones and weather patterns on a global scale. Antwerpen told GlacierHub that “when ice on Greenland melts, there’s a big freshwater influx into the North Atlantic. There are more factors that play into this, but the freshwater influx could increase the likelihood of a slowdown or even a collapse of the AMOC, and this can affect worldwide weather systems, including the monsoon system.”
Despite the progress made by recent studies, researchers remain uncertain of how seasonal factors will affect algal blooms. For example, snowfall over southwest Greenland is projected to increase, potentially delivering more phosphorus to the ice surface as the snow picks up tiny mineral particles and dissolved phosphorus in water droplets, whereas the projected increase in rainfall and surface runoff could hasten the removal of nutrient-containing dust. However, both January 2026 studies suggest that algal blooms may be exacerbating glacier melt, with far-reaching consequences for coastal communities and global ocean systems, and emphasize the importance of conducting further research on processes that change glacier albedo.
To better understand the role of algal feedback loops in glacier melt and the larger threats of sea level rise and global climate change, Antwerpen believes that researchers must continue scaling up their data collection efforts. “We are missing a lot of data. We need more field work, more satellite data, more lab work on the metamorphism of ice and how that works.” Even with these limitations, both studies make important contributions to the field of glacier science and reveal the hidden vulnerabilities of Greenland’s glaciers and ice sheets.
