Mineral Precipitation in North Slope River Icings


  • Dorothy K. Hall




Calcium carbonate, Composition, Groundwater, Icings, Rivers, Water, Alaska, Northern


Powdered calcium carbonate (CaCO3) patches averaging 4 cm in thickness were found on icings (aufeis fields) in the Canning and Shaviovik Rivers in northeastern Alaska. The presence of this material on aufeis suggests that much of the water which feeds the aufeis is coming from depth and has flowed through calcareous bedrock. Aufeis forms during the winter at or below the point where groundwater discharges, or when river water is forced upwards through cracks in river ice. Calcium carbonate in solution in the groundwater is excluded as the water freezes during ice growth. The CaCO3 slush then accumulates on top of the ice as the aufeis ablates during the melt season. Four patches of CaCO3, covering approximately 0.1% of the total area of the Canning River aufeis were observed during the July 1978 field study. It is estimated that approximately 540 m³ of CaCO3 precipitate were present in the Canning River aufeis in July of 1978. If similar percentages of CaCO3 precipitate were present on other major aufeis fields on the eastern North Slope, approximately 18000 m³ of CaCO3 may be present during a given year in the major North Slope aufeis fields. Most of this precipitate is deposited into the Arctic Ocean via river flow.