[A-CG43] Science in the Arctic Region

[ACG43-11] Recent albedo variation over the Greenland ice sheet

*Teruo Aoki^1,2, Rigen Shimada³, Masahiro Hori⁴, Tomonori Tanikawa⁵, Masashi Niwano⁵ (1.National Institute of Polar Research, 2.SOKENDAI (The Graduate University for Advanced Studies), 3.Earth Observation Research Center, Japan Aerospace Exploration Agency, 4.School of Sustainable Design, University of Toyama, 5.Meteorological Research Institute, Japan Meteorological Agency)

Keywords:albedo, MODIS, Greenland ice sheet, darkening

Satellite-derived surface albedo in the summer season over the Greenland ice sheet (GrIS) shows a decreasing trend from 2000 to 2012, which was termed so-called “surface darkening” of GrIS. However, the interannual variation increased since 2013, and the darkening trend seemingly weakened. In this study, we classified the surface type into snow-covered and bare ice areas from Moderate Resolution Imaging Spectroradiometer (MODIS) data and examined the monthly mean albedo variations in every 1 km elevation zones in each area from April to September using the MODIS albedo product. The results show a statistically significant decrease in surface albedo averaged over the entire GrIS in the summer season during 2000-2012, and a loss of significance during 2000-2020 due to a large interannual fluctuation since 2013. Analyzing the albedo for each elevation zone and each surface type (snow or ice), the change rate in albedo (slope of the regression line) for both surface types is negative for an elevation zone below 1 km in April-August and for all elevation zones in July-August, and positive for all elevations zones in September. However, except for the bare ice area in July below 1 km elevation, there is no statistically significant albedo change for all elevation zones and months. The albedo increase in September suggests a possible increase in snowfall amount and/or frequency. The albedo reduction in July in the bare ice area below 1 km elevation would be due to an expansion of the dark ice area included in that area. On the other hand, the interannual variability in albedo for both snow cover and bare ice areas was larger at lower elevations and seasonally larger in July and August when the air temperatures are higher.