TITLE:
Surface Snow, Firn and Ice Core Composition in Polar Areas in Relation to Atmospheric Aerosol and Gas Concentrations: Critical Aspects
AUTHORS:
Gianni Santachiara, Franco Belosi, Alessia Nicosia, Franco Prodi
KEYWORDS:
Homogeneous Nucleation, Heterogeneous Nucleation, Transfer Function, Scavenging, Riming
JOURNAL NAME:
Atmospheric and Climate Sciences,
Vol.6 No.1,
January
14,
2016
ABSTRACT: The paper
addresses some of the problems surrounding the relation between ice core
chemical signals and atmospheric chemical composition in polar areas. The topic
is important as the reconstruction of past climate and past atmospheric
chemical composition is based on the assumption that chemical concentrations in
the air, snow, firn and ice core are correlated. Ice core interpretation of
aerosol is more straightforward than that of reactive gases. The transfer
functions of gaseous species strongly interacting with ice are complex and
additional field and laboratory experiments are required. Ice core chemical
signals depend on the chemical composition of precipitations, which are related
to the physics of precipitation formation, the chemical composition of the
atmosphere, and post-depositional processes. Published papers reporting data on
the chemical composition of snow seldom consider the fact that crystal
formation and growth in cloud (rimed or unrimed) or near the ground (clear-sky
precipitations), hoar-frost formation and surface riming determine different
chemical concentrations, even assuming constant background concentration in the
atmosphere. This paper discusses the physical and chemical processes affecting
the formation of precipitations in polar areas, and the process of scavenging
gases from non-growing and growing crystals. Attention is mainly focused on the
processes involving nitrate anion in snow, hoar frost and firn. Knowledge of
the chemical relationship between surface snow and atmospheric chemical
concentration could be enhanced by considering specific events, such as snow
falling from cloud, clear sky precipitation, and surface hoar or riming
surface, with simultaneous air sampling. In conclusion, field and laboratory
experiments are still required to study the scavenging processes during
crystal formation.