[A-CG39] 北極域の科学

[ACG39-16] 2019年にグリーンランド氷床で引き起こされた顕著な表面融解域拡大に対する雲放射の影響

*庭野 匡思^1,2、橋本 明弘¹、青木 輝夫^2,1、廣瀬　 聡³、島田 利元⁴、西村 基志²、堀 雅裕⁵ (1.気象研究所、2.国立極地研究所、3.新千歳航空測候所、4.宇宙航空研究開発機構 地球観測研究センター、5.富山大学 都市デザイン学部)

キーワード：グリーンランド氷床、表面融解、雲放射、極域気候モデル、NHM-SMAP

During the summer of 2019, exceptional surface melt occurred over the Greenland ice sheet (Tedesco and Fettweis, 2020; Sasgen et al., 2020). In the previously reported major surface melt event in 2012, clouds played an important role in enhancing surface melt area through the cloud radiative effect (CRE) (Niwano et al., 2015, 2019). In the present study, we utilize the state-of-the-art high resolution (5 km and 1 hour) polar regional climate model NHM-SMAP (Niwano et al., 2018) to investigate CRE on the 2019 summer ice sheet surface melt area expansion. Another previous major surface melt event occurred in 2002 is also investigated. Our NHM-SMAP clear-sky sensitivity simulations based on the method by Niwano et al. (2019) indicates that clouds were responsible for a 0.6%, 3.0%, and 0.4% increase in JJA (June, July, and August) surface melt area extent during 2002, 2012, and 2019, respectively. The smaller atmospheric humidity in 2019, relative to 2012, over the ice sheet despite higher July air temperature anomalies (Tedesco and Fettweis, 2020) affected the contrasting results between 2012 and 2019. However, on the days when the seasonally maximum surface melt areas are estimated (28 June 2002, 12 July 2012, and 30 July 2019, respectively), CRE enhanced surface melt areas by 24.7%, 14.0%, and 26.0%, respectively. These suggest that seasonal frequency and intensity of CRE-induced surface melt events differ considerably year by year.



References:

Niwano, M., Aoki, T., Matoba, S., Yamaguchi, S., Tanikawa, T., Kuchiki, K., and Motoyama, H. (2015): Numerical simulation of extreme snowmelt observed at the SIGMA-A site, northwest Greenland, during summer 2012, The Cryosphere, 9, 971-988. https://doi.org/10.5194/tc-9-971-2015

Niwano, M., Aoki, T., Hashimoto, A., Matoba, S., Yamaguchi, S., Tanikawa, T., Fujita, K., Tsushima, A., Iizuka, Y., Shimada, R., and Hori, M. (2018): NHM–SMAP: spatially and temporally high-resolution nonhydrostatic atmospheric model coupled with detailed snow process model for Greenland Ice Sheet. The Cryosphere, 12, 635-655. https://doi.org/10.5194/tc-12-635-2018

Niwano, M., Hashimoto, A., and Aoki, T. (2019): Cloud-driven modulations of Greenland ice sheet surface melt. Sci. Rep., 9, 10380. https://doi.org/10.1038/s41598-019-46152-5

Sasgen, I., Wouters, B., Gardner, A.S., King, M. D., Tedesco, M., Landerer, F. W., Dahle, C., Save, H., and Fettweis, X. (2020): Return to rapid ice loss in Greenland and record loss in 2019 detected by the GRACE-FO satellites. Communications Earth & Environment, 1, 8. https://doi.org/10.1038/s43247-020-0010-1

Tedesco, M., and Fettweis, X. (2020): Unprecedented atmospheric conditions (1948–2019) drive the 2019 exceptional melting season over the Greenland ice sheet. The Cryosphere, 14, 1209–1223. https://doi.org/10.5194/tc-14-1209-2020