Under-Ice Algae Bloom: Arctic Sea-Ice Primary Production

Long before open water appears, the Arctic spring bloom starts in near-darkness on the underside of the sea ice, where a thin film of ice algae photosynthesizes on whatever sunlight survives passing through snow and ice. This simulator models that light-limited production step directly: a Beer–Lambert extinction stack turns snow depth, ice thickness and sun elevation into an under-ice PAR value, a Steele-curve growth law turns that irradiance into algae biomass, and a grazing term routes the resulting energy into a copepod population that stores it as lipid reserves — the same lipid pool that fuels Arctic cod, seals and, ultimately, polar bears further up the food chain. Thin the snow, thin the ice, or push the sun higher and watch the bloom ignite earlier and harder; pile on grazing pressure and watch copepods crop it back down.