Biogeochemical properties of water in surface ponds on Antarctic fast ice and their relationship with underlying sea-ice properties

Abstract

Surface ponds on Antarctic fast ice were examined by measuring temperature, salinity and concentrations of chlorophyll a (Chl-a), dissolved inorganic carbon (DIC) and nutrients (NO3+ NO2, PO4 and SiO2) in the surface pond water and under-ice water. Sea-ice cores were also collected from the bottom of a surface pond (pond-ice core) and from a site away from the pond (bare-ice core). Timeseries measurements of surface pond water temperature showed that it varied with solar radiation rather than with air temperature. Comparison of water properties between surface pond water and under-ice water suggested that DIC and nutrients were consumed by biological productivity during pond formation. Depth profiles of nutrient concentrations in the pond-ice core suggested the remineralization of organic matter at the bottom of the surface pond. The Chl-a concentration was lower at the bottom of the pond-ice core than in the bare-ice core, suggesting that surface pond formation reduces ice algae abundance in sea ice because meltwater flushes algae from the porous sea ice into the under-ice water.