Transformations of Snow Chemistry in the Boreal Forest:
Accumulation and Volatilization
J. Pomeroy1, T.D. Davies2, H.G. Jones3, P. Marsh1,
N.E. Peters4, and M. Tranter5
This paper examines the processes and dynamics of inorganic chemical accumulation and loss in
boreal forest snow during the cold winter period. Field observations from Inuvik, NWT, and
Waskesiu, Saskatchewan, and process-based modeling are used to link chemical transformations
and physical processes in boreal forest snow. Through dry deposition and episodic wet deposi-
tion, inorganic N and S are incorporated in intercepted snow and surface snow over the winter
season. Dry deposition rates of N increase by an order of magnitude when the snow surface tem-
perature approaches the melting point. However, N is not well conserved by snow over the win-
ter. N is lost from snow that has been physically transformed through sublimation (intercepted
snow) and kinetic metamorphism (surface snow). The loss of N during these processes is roughly
proportional to the loss of SWE from surface or intercepted snow. Measured and modeled esti-
mates of snow loss from intercepted snow sublimation and strong kinetic metamorphism suggest
a subsequent enrichment of S but not N, a result matched by field data.
Climate, canopy, and snow structure therefore strongly affect most of the factors important to
over-winter snow chemical fluxes. In warmer zones of the southern boreal forest, N losses due to
intercepted snow sublimation and N + S gains due to dry deposition to wet snow are important,
but N losses due to metamorphism are not, a situation reversed in the northern zones near the
subarctic. Besides a marked climate sensitivity, the sensitivity to structure of the forest canopy
means that alteration of the native forest through burning, harvesting, and replanting will have
strong consequences for winter chemical fluxes.
1
National Hydrology Research Institute, Environment Canada, 11 Innovation Boulevard, Saskatoon,
Saskatchewan S7N3H5, Canada
2 Climate Research Unit, University of East Anglia, Norwich, NR4 7TJ United Kingdom
3 Institut National de la Recherche Scientifique, Universit du Qubec, CP 7500, 2700 Einstein Ste-Foy,
Qubec G1V 4C7, Canada
4 USGS, 3039 Amwiler Road, Atlanta, Georgia 30360-2824, USA
5 University of Geographical Sciences, University of Bristol, Bristol, BS8 1SS, United Kingdom
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