4. Conclusions
We investigated the effects of snow cover on the vertical distribution of nutrient concentrations and the long-term remineralization process in multi-year, Antarctic fast sea ice. We analyzed thin sections to determine the ice structure, which confirmed the upward growth of fast ice by the year-by-year formation of snow-origin ice. Vertical profiles of biogeochemical components in the ice showed that the high nutrient concentrations of first-year ice are transported downward by the subsequent formation of new snow-origin ice, eventually forming multi-year ice. Because the atmospheric nutrient supply is limited by the purity of Antarctic snow, nutrient concentrations in snow-origin ice decreased as the snow fraction increased.
Nutrients incorporated into columnar ice of seawater origin were dominantly processed by biological uptake via primary production during the first year, but remineralization of degrading organic matter by heterotrophic organisms and bacteria resupplied nutrients to multi-year ice. By analyzing data on first-year and multi-year ice spanning several years in the same area, it was possible for the first time to determine the long-term cycling of nutrients in fast ice.