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.