[A-CG39] 北極域の科学

[ACG39-P14] 北西グリーンランド氷床上SIGMA-Aサイトで観測された雪面熱収支の特徴

*廣瀬 聡¹、青木 輝夫^2,3、庭野 匡思³、的場 澄人⁴、谷川 朋範³、山口 悟⁵、山崎 哲秀⁶ (1.気象庁新千歳航空測候所、2.国立極地研究所、3.気象庁気象研究所、4.北海道大学低温科学研究所、5.防災科学技術研究所雪氷防災研究センター、6.アバンナット北極プロジェクト)

キーワード：熱収支、クオリティーコントロール、自動気象観測装置、グリーンランド氷床、アルベド

The Greenland ice sheet (GrIS) has been losing snow and ice mass at an accelerating rate since the late 1990s due to surface melting and ice discharge into the surrounding ocean (Rignot et al., 2011), and there are concerns about the impact on sea level rise. In July 2012, a record surface melting event occurred across the Greenland ice sheet (Nghiem et al., 2012). In this study, we investigated the surface energy balance by using the data obtained with an automated weather station (AWS) which was installed through the SIGMA project (Aoki et al., 2014) to clarify the contributing factors to surface melting. The AWS is located at the SIGMA-A site (78°03’N, 67°38’W, 1,490 m a.s.l.) on the northwest GrIS and the study period is from 30 June 2012 to 31 December 2019. We performed quality control prior to data analysis. Our analysis showed that the amount of surface melting increased in years with warm summers, when downward sensible heat transport and net shortwave radiation increased. Positive feedback between snow grain growth and near-infrared albedo reduction played an important role in the melting process. The relationship between the North Atlantic Oscillation index and surface melt flux revealed that July 2012 was an extraordinary year, characterised by an increase in melting caused partly by increased downward longwave radiation from low-level clouds, which suppressed net longwave cooling, and partly by the increases in sensible heat flux and net shortwave radiation that are generally associated with warm summers.