山岳氷河の質量・水収支の経年変動

• Main Authors: 知北, 和久, 和田, 知之, 工藤, 勲, キム, ヨンオン
• Format: Article in Journal/Newspaper
• Language: Japanese
• Published: 北海道大学大学院理学研究院自然史科学部門（地球物理学）
• Subjects: 450; Cascade Glacier; glacier; glaciers; Alaska
• Online Access: http://hdl.handle.net/2115/49051; https://doi.org/10.14943/gbhu.75.1

Meteorological and hydrological data for a drainage basin of a mountain glacier, the Gulkana Glacier, Alaska, monitored by U. S. Geological Survey (USGS) for more than 40 yrs, are corrected and retrieved. Interannual variations of daily mean air temperature and daily precipitation near the glacier and daily runoff rate at a proglacial stream averaged over the ablation period (June to September) indicate that the increasing rates of 1968－2010 and 1985－2010 are 0.012 ℃/yr and 0.014 ℃/yr, 0.024 mm/yr and 0.041 mm/yr, and 0.092 mm/yr and 0.25 mm/yr, respectively. Thus, the runoff rate and precipitation tend to increase greatly in the recent years. The daily glacier-melt runoff rate averaged over the ablation period was obtained on the assumption of zero englacial water storage change over the period. As a result, the glacier-melt runoff rate exhibits the linear relationship with the daily mean air temperature near the glacier. The summer ablation of the glacier was larger than the winter accumulation in many years, consequently indicating that the net mass balance is negative in almost all the years. Especially since 1988, the net mass balance is negative in any years. The tendency of greatly negative cumulative net mass balance since 1988 suggests that the glacier thickness become zero in ca. 2160. Meanwhile, the glacier area tends to decrease greatly and linearly since 1993 at the rate of -0.18 km2/yr. This indicates that the glacier area would be zero in ca. 2096. The large decrease of cumulative net mass balance since 1980’s is common to the three glaciers, Gulkana, Wolverine and South Cascade, monitored by USGS since 1960’s. The decreasing rate of glacier thickness in 1980’s to 2004 is -0.74 m/yr for Gulkana Glacier, -0.78 m/yr for Wolverine Glacier, and -0.71 m/yr for South Cascade Glacier, thus showing the similar tendency in thinning.