Preface（巻頭言）

抄録

    This Special Issue (Volume 32) comprises the research results and related studies from the first half of the period from 2011-2015 of the “Snow Impurity and Glacial Microbe effects on abrupt warming in the Arctic” (SIGMA) Project funded by the Japan Society for the Promotion of Science (JSPS) Grant-in-Aid for Scientific Research (S) number 23221004 (http://www.mri-jma.go.jp/Dep/cl/cl6/sigma/sigma-e.html). The scientific background of the SIGMA Project is that many climate models cannot sufficiently simulate recent abrupt snow/ice melting in the Arctic. One of the possible causes for this limitation is albedo reduction due to light-absorbing snow impurities (LASI) such as black carbon (BC) and glacial microbes. We are conducting field campaigns mainly in the Qaanaaq areas of northwest Greenland where abrupt melting is occurring in addition to meteorological and snow observations in Japanese snow areas to better understand the contribution of light-adsorbing snow impurities to snow/ice melting. Snow metamorphism and albedo process model and glacial microbe model are being developed and incorporated into earth system model (EMS) of the Meteorological Research Institute. In the second half of the project, we will simulate the recent and future climates and clarify the quantitative contributions of BC and glacial microbes on the recent abrupt melting in the Arctic. A shallow ice core drilling on the Greenland ice sheet will also be conducted in 2014, by which the atmospheric aerosols and snow impurities after the Industrial Revolution will be reproduced. Furthermore, the temporal-spatial variations of snow physical parameters such as snow grain size and concentrations of LASI and glacial microbes will be retrieved with satellite remote sensing.
    On the other hand, we consider snow grain size to be an important physical parameter in the SIGMA Project for the following two reasons. Snow grain size is (1) an optical control factor for albedo and (2) a parameter to express snow metamorphism. These two reasons are strongly related to the recent abrupt snow melting in the Arctic through snow- and ice-albedo feedback. The snow grain size is also an important target that assists in monitoring changing snow conditions through satellite remote sensing. We are developing techniques to objectively measure the snow grain size as part of the SIGMA Project. This Special Issue contains those results.
    During the same research period as the SIGMA Project, the “Arctic Climate Change Research Project” (http://www.nipr.ac.jp/grene/e/index.html) as part of “Green Network of Excellence” (GRENE) Program funded by the Ministry of Education, Culture, Sports, Science, and Technology in Japan (MEXT) is conducting. A glaciologist group from the GRENE Arctic Project also chose the Qaanaaq areas in Greenland as their research field. Thus, the SIGMA Project has a strong collaboration with the GRENE Arctic Project and a portion of the collaborative research results also appears in this Special Issue.
    As mentioned above, this Special Issue contains the results of field measurements conducted in Greenland and Japan, laboratory measurements, and satellite remote sensing and modeling studies on snow and ice science of the SIGMA Project and related studies. However, some results related to atmospheric science are not contained in this issue because they are beyond the scope of Bulletin Glaciological Research (BGR).
    As Chief editor of this Special Issue, I sincerely thank this issue’s Editorial board members: Kouichi Nishimura, Hideaki Motoyama, Masahiro Hori, Akihiro Hachikubo, Sumito Matoba, Satoru Yamaguchi, and Nozomu Takeuchi. I also thank the Chief editor of BGR Atsushi Sato for his great support. Finally, I thank the Japanese Society of Snow and Ice for providing an opportunity to publish this issue as a special issue of BGR.