11:00 AM - 1:00 PM
[MIS20-P07] On-site observation of snow grain size between the coast of the East Antarctic Ice Sheet and Dome Fuji, by the Handheld Integrating Sphere Snow Grain Sizer (HISSGraS)
Keywords:East Antarctic Ice Sheet, Snow grain size, Near-infrared reflectance
Albedo in snow areas mainly depends on the grain size and impurity concentration of the snow. In the Antarctic ice sheet, which occupies most of the cryosphere on the earth, snow grain size is the dominant factor for albedo due to the low impurity concentration, and it is essential to understand its wide-area distribution. On the other hand, in the ice core research, it is found that the densification of the firn with small grain size is slower than that with large grain size at Dome Fuji (e.g., Fujita et al., 2009; 2016). Thus, snow grain size and its layer structure are important in determining the densification rate and bubble cloth-off depth of the firn. Therefore, it is necessary to understand the wide-area distribution of snow grain size on the Antarctic ice sheet and the non-uniform distribution of snow grain size at a local area that makes the firn layering. However, wide-area field observations of snow grain size on the Antarctic ice sheet have only been observed by Gallet et al. (2011) and Ohno et al. (2019) at intervals of about 50-100 km from the coast to Dome C and Dome Fuji, respectively. In addition, satellite observation of snow grain size using near-infrared reflectance requires sufficient on-site data for verification. Also, its spatial resolution is too low (for example, 500 m for MODIS sensor λ = 1.64 μm) to observe the non-uniform grain size distribution in the local area than that resolution.
In this study, we observed the grain size of the surface snow and the snow cross-section at unprecedented multi-points in the two round trips from the coast(S16) to Dome Fuji at the 63rd Japanese Antarctic Research Expedition. We used Handheld Integrating Sphere Snow Grain Sizer (HISSGraS) (Aoki, 2018), which enables direct measurement of the snow surface and shortens the measurement time, compared to the previous methods that require sampling snow into a dedicated container for measurement. As a result, we obtained data for two round trips at distances of 20-30 km and 10 surface snow at intervals of about 2 m at each observation site. Furthermore, we observed snow grain size at 3 cm depth increment at 1m cross-section (5.4 m at Dome Fuji) at intervals of about 80-100 km. We find that the 10-point mean value of the surface snow grain size and its variation gradually decrease from the coast to the inland. In this presentation, we also report the depth distribution of snow grain size, changes of the average and horizontal variation of surface snow grain size in the range of about 20 m, and their coast to Dome Fuji distribution between two round trips.
Fujita, S. et al. Densification of layered firn in the ice sheet at Dome Fuji, Antarctica. J. Glaciol. 62, 103–123 (2016).
Fujita, S., Okuyama, J., Hori, A. & Hondoh, T. Metamorphism of stratified firn at Dome Fuji, Antarctica: A mechanism for local insolation modulation of gas transport conditions during bubble close off. J. Geophys. Res. 114, F03023 (2009).
Gallet, J.-C., Domine, F., Arnaud, L., Picard, G. & Savarino, J. Vertical profile of the specific surface area and density of the snow at Dome C and on a transect to Dumont D’Urville, Antarctica – albedo calculations and comparison to remote sensing products. The Cryosphere 5, 631–649 (2011).
Ohno, H. et al. Measurement of the Specific Surface Area of Surface Snow during JARE59 Inland Traverse. JSSI and JSSE Joint Conference on Snow and Ice Research. (2019).
Aoki, T. et al. Development of Handheld Integrating Sphere Snow Grain Sizer (HISSGraS). JSSI and JSSE Joint Conference on Snow and Ice Research. (2018).
In this study, we observed the grain size of the surface snow and the snow cross-section at unprecedented multi-points in the two round trips from the coast(S16) to Dome Fuji at the 63rd Japanese Antarctic Research Expedition. We used Handheld Integrating Sphere Snow Grain Sizer (HISSGraS) (Aoki, 2018), which enables direct measurement of the snow surface and shortens the measurement time, compared to the previous methods that require sampling snow into a dedicated container for measurement. As a result, we obtained data for two round trips at distances of 20-30 km and 10 surface snow at intervals of about 2 m at each observation site. Furthermore, we observed snow grain size at 3 cm depth increment at 1m cross-section (5.4 m at Dome Fuji) at intervals of about 80-100 km. We find that the 10-point mean value of the surface snow grain size and its variation gradually decrease from the coast to the inland. In this presentation, we also report the depth distribution of snow grain size, changes of the average and horizontal variation of surface snow grain size in the range of about 20 m, and their coast to Dome Fuji distribution between two round trips.
Fujita, S. et al. Densification of layered firn in the ice sheet at Dome Fuji, Antarctica. J. Glaciol. 62, 103–123 (2016).
Fujita, S., Okuyama, J., Hori, A. & Hondoh, T. Metamorphism of stratified firn at Dome Fuji, Antarctica: A mechanism for local insolation modulation of gas transport conditions during bubble close off. J. Geophys. Res. 114, F03023 (2009).
Gallet, J.-C., Domine, F., Arnaud, L., Picard, G. & Savarino, J. Vertical profile of the specific surface area and density of the snow at Dome C and on a transect to Dumont D’Urville, Antarctica – albedo calculations and comparison to remote sensing products. The Cryosphere 5, 631–649 (2011).
Ohno, H. et al. Measurement of the Specific Surface Area of Surface Snow during JARE59 Inland Traverse. JSSI and JSSE Joint Conference on Snow and Ice Research. (2019).
Aoki, T. et al. Development of Handheld Integrating Sphere Snow Grain Sizer (HISSGraS). JSSI and JSSE Joint Conference on Snow and Ice Research. (2018).