The nutrient cycle through snow and ice, a review

Abstract

This paper reviews the merging of the nutrient cycle with the water cycle in the seasonal alpine snow cover, emphasizing physical processes at the snowpack and snow grain scale. Nutrients are incorporated into snowflakes growing in the atmosphere, they are part of the dry deposition from the atmosphere to the snowpack and they reach the snow as plant litter. The physical processes of the accumulation of nutrients and their redistribution in and on the snow grains and in the pore space of the snow matrix are described.The first flush of meltwater that reaches the soil carries a solution of nutrients and acids in a concentration several times higher than bulk values, an effect that increases with the age of the snow and the number of melt/freeze cycles and is more pronounced for sulfate than for chloride. Species that are attached to insoluble particles will be concentrated near the snow surface and will display peak concentrations in the final fraction of meltwater.

Microbial Cell Retention in a Melting High Arctic Snowpack, Svalbard

“…5) is the major difference between cell abundance and solute concentration, such that as much as 70% of z SWE loss was needed to elute 50% of the accumulated cells. Similar patterns to these cell transfer dynamics have been described for hydrophobic substances and particles during snow melt, which aggregate and become trapped within the snow or at the snow surface and are thus released only at the very end of the melting period (Kuhn, 2001;Meyer et al, 2006;Meyer and Wania, 2008;Meyer et al, 2009aMeyer et al, , 2009b. Soluble species, on the other hand, will tend to have an elution sequence that is governed by the age of the snow and snow melt characteristics depending on the melt-freeze frequencies (Meyer et al, 2009a).…”

“…The elution of ions was assumed to follow the well-established sequences (e.g., Kuhn, 2001), while the behavior of microbial cells was assumed to depend on their relative location within the snow crystals (i.e., as ice nuclei or wind deposited) and/or ability to aggregate.…”

“…The process of snow formation within the atmosphere requires a nucleation surface to initiate freezing (Colbeck, 1981). This nucleation surface is usually composed of ice splinters, clay particles, or other water-insoluble substances (Kuhn, 2001). Indeed, cloud condensation and ice nucleation within the atmosphere can also be catalyzed by biological agents, such as bacteria or fungal spores (see Jayaweera and Flanagan, 1982;Morris et al, 2007;Christner et al, 2008;Delort et al, 2010), even though the significance of these processes might be of minor importance when other nuclei are abundant (Junge and Swanson, 2008;Diehl and Wurzler, 2010;Hoose et al, 2010).…”

“…When a snowflake grows in the atmosphere, or precipitates, it can absorb gases, aerosols, and supercooled droplets (Colbeck, 1981;Abbatt, 1997;Kuhn, 2001;Hoog et al, 2007). The large surface area of snowflakes leads to an efficient scavenging and removal of atmospheric pollutants (Chang, 1984;Barrie, 1991;Lei and Wania, 2004), which then end up in the snow cover.…”

“…When snow melt starts, elution of its solutes occurs, and the first meltwater will be enriched in ions compared to the snowpack (e.g., Lilbaek and Pomeroy, 2008); typically, the first 20-30% of the meltwater will contain 50-80% of the snowpack solutes (Johannessen et al, 1975;Bales et al, 1989 (Kuhn, 2001, and references therein), but depends on the characteristics of the snowpack, for instance on the amount of melt/freeze cycles before and during melt (Colbeck, 1981;Brimblecombe et al, 1986;Bales et al, 1989;Cragin et al, 1996). The elution of chemical solutes, including nutrients, then affects both the microbial habitats within the snow (Hodson, 2006;Larose et al, 2010a), and underlying soils and ice layers (Jones, 1991(Jones, , 1999Schmidt et al, 1999;Edwards et al, 2007), but also ecosystems downstream (e.g., Gagne et al, 2009).…”