10:45 AM - 12:15 PM
[ACC26-P06] Evolution of firn density and microstructure near the surface at multiple sites around Dome Fuji, Antarctica
Keywords:firn, density, microstructure, Dome Fuji, surface process, Antarctica
We find large variation in density and the absence of overall density increase within ~0–2 m around Dome Fuji. According to semi-empirical densification models, small densification rate is expected from the small overburden pressure near the surface, but the modeled densification rate is still clearly larger than the data. We also find the developments of vertical elongation of ice and pores, and decrease of SSA within ~0–2 m where seasonal and diurnal temperature variations create large temperature gradients. From these ovservations, we suggest that temperature-gradient metamorphism is an important factor for the formation and development of firn microstructure and layering near the surface, and that part of sublimated water vapor in the firn may escape to the atmosphere to lose the firn mass (density decrease) near the surface. Furthermore, we find more developed vertical elongation and SSA decrease at low accumulation sites than at high accumulation sites, suggesting that the exposure time of a firn layer to the temperature gradients near the surface may determine the magnitude of near-surface metamorphism.
Reference:
Calonne, N. et al.: The layered evolution of fabric and microstructure of snow at Point Barnola, Central East Antarctica, Earth and Planetary Science Letters, 460, 293–301, 2017.
Moser, D. E. et al.: Microstructure of Snow and Its Link to Trace Elements and Isotopic Composition at Kohnen Station, Dronning Maud Land, Antarctica, Front. Earth Sci., 8, 23, 2020.
Oyabu, I. et al.: Temporal variations of surface mass balance over the last 5000 years around Dome Fuji, Dronning Maud Land, East Antarctica, Climate of the Past, 19, 293–321, 2023.