The effect of refreezing on the isotopic composition of melting snowpack

✍ Scribed by Shiqiao Zhou; Masayoshi Nakawo; Shigemasa Hashimoto; Akiko Sakai

• Publisher: John Wiley and Sons
• Year: 2008
• Tongue: English
• Weight: 208 KB
• Volume: 22
• Category: Article
• ISSN: 0885-6087
• DOI: 10.1002/hyp.6662

✦ Synopsis

Abstract

The isotopic composition of solid and liquid portions of natural melting snowpack is investigated in detail by the separating of liquid water from snow grains at different depths of the snowpack. The slope of the δD–δ^18^O line for the liquid phase is found to be lower than for the solid phase. This is proved to be due to the isotopic fractionation occurring in the melt–freeze mass exchange within the snowpack. Melting of the snowpack has no clear impact on the δD–δ^18^O line for the solid phase, but the slope of the δD–δ^18^O line for the liquid shows an overall slight decrease in the melting period. When the snowpack is refrozen, the refreezing process would inevitably cause the slope of the solid phase to decrease because of the discrepancy between the slopes of the two phases. Thus the slope of the solid would become lower and lower as the diurnal melt–freeze episodes cycle throughout the melting season. This effect is then demonstrated by looking into the isotopic composition changes of glacier firn. The extent of the effect depends on the snowpack properties and environmental conditions. The slope changes also result in a decreasing trend in deuterium excess. Copyright © 2007 John Wiley & Sons, Ltd.