To clarify the factors contributing to surface melting, we investigated the surface energy balance at the SIGMA-A site on the northwest Greenland ice sheet from 2012 to 2019 using meteorological data observed at an automated weather station. We performed quality control prior to data analysis. Our analysis showed that the amount of surface melting increased in years with warm summers, when 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 a significant increase in melting caused partly by increased downward longwave radiation from the lower clouds, which suppressed net longwave cooling, and partly by the increases in sensible heat and net shortwave radiation that are generally associated with warm summers.
Knowledge of the variability of sea ice thickness is insufficient because the existing methods have some weaknesses. We applied Unmanned Aerial Vehicle with Structure from Motion (UAV-SfM) to estimate sea ice freeboard on the coast of Qaanaaq, NW Greenland. Three aerial photography methods were attempted to find an efficient way for surveying various sea ice using multi-rotor and fixed-wing UAVs. The UAV-SfM surveys with ground control points (GCP) layout generate a distribution map of freeboard with poor reproducibility. The main causes are the difficulty of dense GCP layout on various sea ice and change of GCP positions by tidal change. The UAV-SfM surveys without GCP (i.e., using precise geotagged image data) improved the operating efficiency in the harsh cold environment and generated a highly reproducible distribution map of freeboard. A fixed-wing UAV mounting camera equipped with a large image sensor is suitable for detecting small changes in the flat sea ice surface over a wide range. Further validation and technical improvement are required for practical application to sea ice thickness estimation.
Currently occurring rapid warming in the Arctic could affect global environmental changes through sea level rise and remote atmospheric effect. The surface melting of the Greenland Ice Sheet (GrIS) involves various uncertainties, which are issues to be elucidated for accurate climate projections. To clarify how the atmosphere, snow/ice, and glacial microbes in the GrIS affect the ice sheet change under global warming, the SIGMA and SIGMA-II projects were conducted from FY2011 to FY2019. In parallel, big Arctic research projects such as GRENE and ArCS were also done, which accelerated the Japanese Greenland researches. This paper describes the research results of the SIGMA and SIGMA-II projects as well as the related research projects in the categories of (1) in-situ observations of the atmosphere, snow/ice, and glacial microbes, (2) ice core drilling, (3) satellite observation, and (4) numerical modeling. Furthermore, we discuss current issues in these studies, a linkage to the Cryosphere subject of recently launched ArCS II Project, and the importance of capacity building.