Paleoclimatic implication of buried peat layers in a subalpine snowpatch grassland on Mt. Zarumori, northern Japan

We reconstruct the paleoclimatic background of buried peat layers formed around the 10th century, which occur in a snowpatch grassland in a snowy mountain in northern Japan. In the snowpatch grassland, peat accumulation is presently restricted by the presence of a summer snowpatch. Thus, the buried peat layers imply that the summer snowpatch around the 10th century was smaller than it has been in recent times. Climatic control of the year-to-year variation of the present snowpatch was examined based on a snowpatch survey and analysis of meteorological data. The observed snowpatch profiles suggested that winter wind speed played an important role in controlling summer snowpatch size. The buried peat layers indicate not only warming in the melt season, but also a possible weakened winter monsoon in the Medieval Warm Period.