Geochemical denudation rates and solute transport mechanisms in a maritime temperate glacier basin

Abstract

Dissolved cation loss from the basin of Berendon Glacier, northwestern British Columbia is calculated at 947 mequiv m−2 year−1 with calcium accounting for nearly all of this loss. This geochemical denudation rate is substantially greater than the world average of 390 mE m−2 year−1 but agrees well with similar studies from the Cascade Range in the northwestern United States. Abundant precipitation is likely responsible for the significant geochemical denudation despite reduced chemical activity at low annual temperatures. When absorption is considered in the removal process, the major cation denudation rate increases by about 10% and doubles the loss of certain cations such as sodium. This finding complements previously published sedimentological evidence (SEM of quartz grains) of high rates of chemical activity in the basin.Debris–water contact time appears to exert a significant control on the cation and silica concentrations exhibited by the various water types moving through the basin. Firn, glacier ice, and supraglacial streams generally possess the lowest ionic concentrations, and subglacial streams, valleyside streams, and ponds generally contain the highest. The geochemical signature of meltwaters is established rapidly and field-filtering of water samples is critical to the prevention of desorption and mineral dissolution.Anthropogenic chemical input to the Berendon basin is measurable and consists of trace metal rich dust originating at a mining and milling operation close to the glacier terminus. Aeolian transport is responsible for distributing Cu, Cr, Ni, and Pb throughout the watershed; trace metal rich dust could be utilized as a stratigraphic marker for future studies of snow accumulation above the firn line.