Year-to-year variability of solute flux in meltwaters draining from a highly-glacierised basin

Abstract

Electrical conductivity was monitored continuously in the Gornera, which drains the 83% glacierised basin of area 82 km2 containing Gornergletscher, Pennine Alps, Switzerland, during the summer months, in order to provide an indication of meltwater solute content during each of the four years 1979, 1983, 1987 and 1998. Discharge was also recorded between 1970 and 1999. Solute flux, calculated as the product of electrical conductivity and discharge, was used to assess how the year-to-year variability of discharge influences solute transport. Total May through September discharge of the Gornera was in the range −39.1% (1978) to +38.9% (1994) of the 1970–1999 period mean of 118.75×106 m3. The range of variability of July through September electrical conductivity was between −25.0% and +29.1% of the mean of 19.6 μS cm−1 for the four study years. The intra-annual range of total July through September solute flux in the Gornera extended from −22.4% (in 1987, during which, of the four years, discharge for the three months was greatest) to +12.4% (in 1979, when discharge was the lowest) of the four study year means, which represents an average cationic load of ∼25×106 eq. Variability of total solute flux (cv=0.142) was greater than that of total discharge (cv=0.127) in the three month period over the four years. Considerable intra-annual variability of total discharge over the three decades suggests that the total annual solute flux also fluctuated significantly from year to year.