SNOSP: Ion deposition and concentration in high alpine snow packs

Abstract

The present paper summarizes the results of SNOSP, a snow sampling program carried out in the Alps in the years from 1991 to 1993 in order to study the chemical composition of the high alpine snow pack. The paper briefly describes the sampling sites and the procedures used, focussing then on the geographical, seasonal and year to year variation of the mean concentration and total deposition of eight major ions, viz., chloride, nitrate, sulfate, ammonium, sodium, potassium, magnesium and calcium. NH4+, NO3− and SO4= concentrations in spring snow are higher by a factor of two to three than in winter snow since the lower tropospheric convection is confined to the valleys in winter and extends beyond glacier altitudes in spring. This underlines the importance of local and regional versus long range transport of contamination to the high elevated sites. The Ca++ deposition occurs in single events (e.g., dust input from the Sahara) with a slightly higher incidence in spring that is consistent with the annual course of atmospheric circulation patterns. Most ionic species display a west to east increase of concentration by about one third. The prevailing precipitation patterns have opposite gradients so that total ionic load of the respective snowpack has no regional preference. The seasonal contrast as expressed by ratios of spring to winter concentrations of NH4+, NO3− and SO42− is stronger in the west than in the east, and the east to west contrast is greater in winter than in spring.

Nutrients and organic matter in a glacial river—floodplain system (Val Roseg, Switzerland)

“…High concentrations of total nitrogen (primarily DON) together with silica and POC in snow samples collected in April are likely to originate from dry deposition, especially during the end of the snow accumulation period when the lower tropospheric convection extends upward to glacier altitudes (Nickus et al 1997). The importance of aeolian particulates for both ionic and particulate content of the snowpack has been emphasized by several studies (Williams and Melack 1989;Nickus et al 1997; references herein). According to the maps of atmospheric deposition for Switzerland, the deposition of nitrogen in the Val Roseg catchment is 10-15 kg N ha Ϫ1 yr Ϫ1 (Rihm 1996).…”

The impact of Saharan dust and black carbon on albedo and long-term mass balance of an Alpine glacier

“…The same also applies to variations with altitude: at higher elevation, ion concentrations are lower compared to valleys, but the general increase in precipitation with elevation compensates for this effect, so that ionic loads are expected to be in the same order of magnitude independent of absolute elevation. A more detailed investigation of selected sampling locations in the vicinity of Colle Gnifetti/Fiescherhorn (Breithorn, Gorner-/Theodulgletscher, Colle Vincent, Jungfraujoch) revealed that there is no distinct altitudinal trend in ionic loads (Nickus et al, 1997). A recent study about atmospheric deposition in alpine and subalpine areas confirms these results and concludes that there are no clear regional gradients, but a significant spatial variability of atmospheric ion deposition over the Alps (Rogora et al, 2006).…”

“…In addition, a unique data set of monthly means of global solar radiation for Davos, covering the period 1936-2014, is provided by the Global Energy Balance Archive (GEBA; Ohmura et al, 1989), and was employed to improve the performance of the cloud factor parameterization. A firn/ice core from the cold glacier saddle of Colle Gnifetti (4455 m a.s.l., Monte Rosa, Switzerland), retrieved in 2003, provides a continuous record of annual iron (Fe) concentrations over 1914-1997(Sigl, 2009, which was used to infer the mineral dust concentration in precipitation (Fig. 2a).…”

“…Several studies performed detailed investigations of the regional and altitudinal distribution of major ions in the high Alpine region (e.g., Nickus et al, 1997;Rogora et al, 2006). They found a marked regional variability but no clear trends, neither in distance nor in altitude.…”

“…For this reason, we relied on time series at locations other than Claridenfirn and had to transpose the measurements to the study site for which long-term mass balance measurements were available. In the 1990s a large-scale study about the chemical composition of high-alpine winter snow packs was carried out in the Alps with the aim of detecting the regional and altitudinal distribution of major ions (SNOSP; Nickus et al, 1997). It was found that the concentration of most ionic species in winter snow increases by about one-third from west to east and that ionic loads show no regional preference due to opposite gradients in the prevailing precipitation patterns.…”