Glacier type drive Greenland fjord productivity: a Lipid seascape perspective

Arctic fjord ecosystems are undergoing rapid changes due to climate warming, glacier retreat, and shifts in oceanography, with significant implications for biogeochemical cycling and biological productivity. As glaciers retreat and discharge increases, fjords are becoming fresher, and fjord morphology is changing, altering circulation, vertical structure, and the light environment. Traditionally, fjords with marine-terminating glaciers have been considered more productive due to nutrient renewal from subglacial discharge plumes. However, this relationship is more complex, as productivity depends not only on mixing mechanisms but also on nutrient concentrations, phytoplankton presence, and light availability. This study examines lipid concentrations and isotopic compositions across different Greenlandic fjord systems. These systems encompass diverse conditions, from eutrophic waters in West Greenland, influenced by nutrient-rich Atlantic inflows, to oligotrophic waters in East Greenland, shaped by polar waters and glacial melt. Our data revealed distinct regional differences linked to external forcings. West Greenland exhibits higher lipid concentrations and isotopic values, driven by marine phytoplankton and influenced by Arctic and North Atlantic currents. In contrast, East Greenland’s lipid profiles are shaped by polar waters, and sea ice algae with lower isotopic values linked to terrestrial runoff. These findings highlight the interconnectedness between fjord ecosystems and broader climatic and oceanic drivers, underscoring the importance of external boundary conditions in predicting the future of fjord productivity. The impact of climate warming and sea ice melting will be therefore spatially different and strongly dependent on the distinct oceanographic processes within the different regions. By linking fjord morphology and regional oceanography to productivity, this work highlights the need to integrate internal fjord dynamics with external boundary conditions to predict future ecosystem productivity in Arctic fjords.