Spatial variability of the major chemistry of the Antarctic ice sheet

A compilation of reliable data for sodium, nitrate, chloride and sulphate has been made. NO3 concentrations arc remarkably consistent across Antarctica, though there appears to be some correlation with altitude and accumulation rate. Post-depositional loss of N03- is important at low-accumulation sites. CI concentration (either measured directly or calculated from Na + via the seasalt ratio) decreases with distance from the coast, though the decline is less rapid if the coastal topography is not steep or mountainous. Excess sulphate (xs SO42-) concentration (here calculated from normal sea-salt ratios with Na+ or Cl ) also declines with distance from the coast, though less quickly than CI-. Fractionation of sea-salt ions makes the calculation of xs SO42- uncertain.