10:15 AM - 10:30 AM
[MIS15-06] Recent Glacier Shrinkage on Tropical High Mountains in Africa
-Impacts on the surrounding water environment and the lives of local residents-
★Invited Papers
Keywords:Tropical high mountain, Glacier reduction, Water environment, Local community, Stable isotope
In this study, we investigated the impact of glacier reduction on the water environment and water resources in the surrounding area of Mt. In the foothill area of the study area (about 2,000 m), there is little precipitation and people are dependent on river water and spring water from Mt. Kenya. However, the relationship between these water resources and the diminishing glaciers has not been clarified.
We attempted to estimate the recharge elevation of river water and spring water used by the residents at the foot of the mountain using the isotope altitude effect line calculated from precipitation samples of Mt. Kenya. As a result, the recharge elevations of river water and spring water at the foot of the mountain were estimated to be about 4,650 m and 4,700 m, respectively, indicating that snowmelt and glacier meltwater at high elevations are likely to contribute to the water resources at the foot of the mountain. In addition, the water level of the Naromol River in the western foothills of Mt. Kenya has been decreasing from 1985 to 2015, and during the field survey, it was found that the crop species that can be cultivated due to the decrease in water resources are limited to those that are resistant to drought (potatoes, wheat, corn, etc.).
The measurement of tritium and CFCs in the spring water at the foot of Mt. Kenya revealed that the water has been gushing into the foot of the mountain for 40 to 60 years since the time of recharge at the mountain body. These results suggest that snowmelt and glacier melt water from the past high altitude zone penetrated the ground, flowed down for 40 to 60 years, and gushed out to the present foot of the mountain.
The glacier of Kilimanjaro (5,895 m) is decreasing rapidly due mainly to global climate change. In addition, Kilimanjaro plays an important role as a regional water catchment, also called "Water Tower." Hence, in this study, based on the analysis of the glacier reduction area in recent years, we aim to elucidate the possibility that melting water from the shrinking glacier contributes to the hillside river water using the satellite image analysis and isotope analysis.
The results of previous research and satellite image analysis show that the glaciers of Kilimanjaro have been shrinking at a fast rate during the period 1912-2019. The mean annual reduction area of glaciers has been increasing at 0.066 km2 (1989-2000), 0.067 km2 (2000-2010), and 0.088 km2 (2010-2019), and if this rate continues, it is expected that glaciers will disappear from Kilimanjaro around 2030. As a result of oxygen and hydrogen isotope ratio analysis of river water and glacier meltwater, hillside river water in the dry season(δ18O =−6.48‰ to −5.87‰, δD=−42.44‰ to −37.36‰, 3,939m to 4,579m)is more similar to glacier meltwater near the summit (δ18O =−6.03‰ to −5.14‰, δD=−48.19‰ to −39.02‰) than to precipitation in the high altitude zone (δ18O=−2.41‰, δD=−3.6‰, 4,360 m), which indicates the contribution of glacier meltwater to hillside river water.
In Kilimanjaro, most of the climbers visit in the dry season. If the glaciers will disappear in the future and fill up the river water which is essential for running camps, the local tourism industry may be affected.
We attempted to estimate the recharge elevation of river water and spring water used by the residents at the foot of the mountain using the isotope altitude effect line calculated from precipitation samples of Mt. Kenya. As a result, the recharge elevations of river water and spring water at the foot of the mountain were estimated to be about 4,650 m and 4,700 m, respectively, indicating that snowmelt and glacier meltwater at high elevations are likely to contribute to the water resources at the foot of the mountain. In addition, the water level of the Naromol River in the western foothills of Mt. Kenya has been decreasing from 1985 to 2015, and during the field survey, it was found that the crop species that can be cultivated due to the decrease in water resources are limited to those that are resistant to drought (potatoes, wheat, corn, etc.).
The measurement of tritium and CFCs in the spring water at the foot of Mt. Kenya revealed that the water has been gushing into the foot of the mountain for 40 to 60 years since the time of recharge at the mountain body. These results suggest that snowmelt and glacier melt water from the past high altitude zone penetrated the ground, flowed down for 40 to 60 years, and gushed out to the present foot of the mountain.
The glacier of Kilimanjaro (5,895 m) is decreasing rapidly due mainly to global climate change. In addition, Kilimanjaro plays an important role as a regional water catchment, also called "Water Tower." Hence, in this study, based on the analysis of the glacier reduction area in recent years, we aim to elucidate the possibility that melting water from the shrinking glacier contributes to the hillside river water using the satellite image analysis and isotope analysis.
The results of previous research and satellite image analysis show that the glaciers of Kilimanjaro have been shrinking at a fast rate during the period 1912-2019. The mean annual reduction area of glaciers has been increasing at 0.066 km2 (1989-2000), 0.067 km2 (2000-2010), and 0.088 km2 (2010-2019), and if this rate continues, it is expected that glaciers will disappear from Kilimanjaro around 2030. As a result of oxygen and hydrogen isotope ratio analysis of river water and glacier meltwater, hillside river water in the dry season(δ18O =−6.48‰ to −5.87‰, δD=−42.44‰ to −37.36‰, 3,939m to 4,579m)is more similar to glacier meltwater near the summit (δ18O =−6.03‰ to −5.14‰, δD=−48.19‰ to −39.02‰) than to precipitation in the high altitude zone (δ18O=−2.41‰, δD=−3.6‰, 4,360 m), which indicates the contribution of glacier meltwater to hillside river water.
In Kilimanjaro, most of the climbers visit in the dry season. If the glaciers will disappear in the future and fill up the river water which is essential for running camps, the local tourism industry may be affected.