A Firn Densification Process in the High Accumulation Dome of Southeastern Greenland

• Published in: Arctic, antarctic, and alpine research Vol. 49; no. 1; pp. 13 - 27
• Main Authors: Iizuka, Yoshinori, Miyamoto, Atsushi, Hori, Akira, Matoba, Sumito, Furukawa, Ryoto, Saito, Takeshi, Fujita, Shuji, Hirabayashi, Motohiro, Yamaguchi, Satoru, Fujita, Koji, Takeuchi, Nozomu
• Format: Journal Article
• Language: English
• Published: Boulder Institute of Arctic and Alpine Research (INSTAAR), University of Colorado 01.02.2017; Taylor & Francis; Institute of Arctic and Alpine Research; Taylor & Francis Ltd
• Subjects: Accumulation; Firn; Viscosity coefficient; PN, Arctic
• ISSN: 1523-0430; 1938-4246
• DOI: 10.1657/AAAR0016-034

We examine a firn core from a dome in southeast Greenland that exhibits distinct firn densification. The ice was -20.9 °C at 20 m depth, and the core gives an average accumulation rate of 1.0 m w.e. yr-1 in water equivalent. However, the close-off density of 830 kg m-3 occurs at 83.4–86.8 m depth, which is about 20-m shallower than that obtained from two empirical models. Where the density ρ > 750 kg m-3, the densification appears faster than that from the empirical models. As a result, compared to the empirical coefficient, the actual compactive viscosity coefficient is nonlinear and decreases at ρ > 750 kg m-3, indicating that the firn with a higher density is softer than that from the empirical result. We argue here that the high accumulation rate creates a high overburden pressure in a short time. Thus, the relative softness of the firn may arise from (1) there being not enough time to form bonds between grains as strong as those in a lower accumulation-rate area, and similarly, (2) the dislocation density in the firn being relatively high.