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[MIS23-P01] Characteristics of mass balance of mounrain glaciers in the northern part of the northern Japanese Alps
Keywords:glacier, mass balance , SfM, northern Japanese Alps, perennial snow patch
1. Introduction
In recent years, seven glaciers were confirmed in the northern Japanese Alps (Arie et al., 2019). It is necessary to measure accumulation and ablation separately to understand the factors of glacier mass balance changes.
Fukui et al. (2018) measured the mass balance of the Gozenzawa glacier from 2012 to 2016 by the stake method. However, the summer and winter balance has not been measured due to the stakes were buried in winter.
In this study, we calculated the mass balance of five glaciers in the northern Japanese Alps from 2015 to 2019 by geodetic methods using Cessna aerial images and SfM-MVS technology. The annual mass balance, winter balance, and summer balance were calculated. In addition, the mass balance gradient and mass balance amplitude are obtained from the calculated annual mass balance, winter balance, and summer balance of glaciers. Moreover, we discussed the characteristics of the mass balance of glaciers in the northern Japanese Alps by comparing them with glaciers in the world.
2. Method
Digital surface models (DSMs) of glaciers at the end of snowmelt season and the maximum snowfall season were created using continuous aerial images of glaciers acquired by Cessna aerial photography and SfM-MVS technology. By comparing the DSM at the end of snowmelt season, at annual intervals, the relative altitude change of the glacier was calculated. In addition, the relative altitude changes of glaciers in winter and summer were calculated by comparing the DSM in the maximum snowfall season with in the end of snowmelt season. By integrating the snow density with these relative altitude changes, the annual mass balance, winter balance, and summer balance were calculated.
Regarding the mass balance gradient, each glacier region was divided at altitudes of 10 m, and the mass balance gradient was calculated from the average value of the mass balance in the divided regions.
Regarding the mass balance amplitude, the mass balance amplitude of glaciers in the northern Japanese Alps were calculated using the average value of the results of the winter balance and the summer balance in this study. We also calculated the mass balance amplitudes of glaciers around the world from the average of the winter and summer balances of 188 glaciers recorded in the WGMS.
3. Result
Figure 1 shows the results of the annual mass balance, winter balance, and summer balance of the five glaciers in the northern Japanese Alps. The amount of the annual, winter, and summer balances of the five glaciers were about 10 m (water equivalent). In addition, the winter balance fluctuated greatly from year to year. On the other hand, the summer balance fluctuated almost nothing.
Figure 2 shows the mass balance gradients of the Sannomado glacier and the Komado glacier during the light snow years (2015/2016) and heavy snow years (2016/2017). In 2015/2016, the annual mass was a positive gradient. On the other hand, in 2016/2017, there was a negative gradient. The winter balance gradient of each glacier had almost no gradient in 2015/2016. On the other hand, the winter balance gradient in 2016/2017 was a negative gradient. The summer balance gradient of each glacier was a positive gradient in 2015/2016 and 2016/2017.
Figure 3 shows the average mass balance amplitude of glaciers by region. The mass balance amplitude of glaciers in the northern Japanese Alps was considerably more extensive than that of glaciers worldwide.
4. Discussion
Since the annual fluctuation of the annual mass balance and the annual fluctuation of the winter balance fluctuate in the same tendency, it can be considered that the winter balance determines the annual mass balance of glaciers in the northern Japanese Alps.
The annual mass balance gradient of glaciers in the northern Japanese Alps changed from year to year and having a negative gradient in heavy snow years. In addition, the annual mass balance of all altitude was negative in light snow year and positive in heavy snowfall year. Therefore, it is considered difficult to define the glacier equilibrium line in the glaciers of the northern Japanese Alps.
Furthermore, due to the winter and summer balances of glaciers in the northern Japanese Alps were extremely large, it is considered that the glaciers in the northern Japanese Alps have the highest amount of snowfall and are located in a warm environment among the glaciers in the world.
In recent years, seven glaciers were confirmed in the northern Japanese Alps (Arie et al., 2019). It is necessary to measure accumulation and ablation separately to understand the factors of glacier mass balance changes.
Fukui et al. (2018) measured the mass balance of the Gozenzawa glacier from 2012 to 2016 by the stake method. However, the summer and winter balance has not been measured due to the stakes were buried in winter.
In this study, we calculated the mass balance of five glaciers in the northern Japanese Alps from 2015 to 2019 by geodetic methods using Cessna aerial images and SfM-MVS technology. The annual mass balance, winter balance, and summer balance were calculated. In addition, the mass balance gradient and mass balance amplitude are obtained from the calculated annual mass balance, winter balance, and summer balance of glaciers. Moreover, we discussed the characteristics of the mass balance of glaciers in the northern Japanese Alps by comparing them with glaciers in the world.
2. Method
Digital surface models (DSMs) of glaciers at the end of snowmelt season and the maximum snowfall season were created using continuous aerial images of glaciers acquired by Cessna aerial photography and SfM-MVS technology. By comparing the DSM at the end of snowmelt season, at annual intervals, the relative altitude change of the glacier was calculated. In addition, the relative altitude changes of glaciers in winter and summer were calculated by comparing the DSM in the maximum snowfall season with in the end of snowmelt season. By integrating the snow density with these relative altitude changes, the annual mass balance, winter balance, and summer balance were calculated.
Regarding the mass balance gradient, each glacier region was divided at altitudes of 10 m, and the mass balance gradient was calculated from the average value of the mass balance in the divided regions.
Regarding the mass balance amplitude, the mass balance amplitude of glaciers in the northern Japanese Alps were calculated using the average value of the results of the winter balance and the summer balance in this study. We also calculated the mass balance amplitudes of glaciers around the world from the average of the winter and summer balances of 188 glaciers recorded in the WGMS.
3. Result
Figure 1 shows the results of the annual mass balance, winter balance, and summer balance of the five glaciers in the northern Japanese Alps. The amount of the annual, winter, and summer balances of the five glaciers were about 10 m (water equivalent). In addition, the winter balance fluctuated greatly from year to year. On the other hand, the summer balance fluctuated almost nothing.
Figure 2 shows the mass balance gradients of the Sannomado glacier and the Komado glacier during the light snow years (2015/2016) and heavy snow years (2016/2017). In 2015/2016, the annual mass was a positive gradient. On the other hand, in 2016/2017, there was a negative gradient. The winter balance gradient of each glacier had almost no gradient in 2015/2016. On the other hand, the winter balance gradient in 2016/2017 was a negative gradient. The summer balance gradient of each glacier was a positive gradient in 2015/2016 and 2016/2017.
Figure 3 shows the average mass balance amplitude of glaciers by region. The mass balance amplitude of glaciers in the northern Japanese Alps was considerably more extensive than that of glaciers worldwide.
4. Discussion
Since the annual fluctuation of the annual mass balance and the annual fluctuation of the winter balance fluctuate in the same tendency, it can be considered that the winter balance determines the annual mass balance of glaciers in the northern Japanese Alps.
The annual mass balance gradient of glaciers in the northern Japanese Alps changed from year to year and having a negative gradient in heavy snow years. In addition, the annual mass balance of all altitude was negative in light snow year and positive in heavy snowfall year. Therefore, it is considered difficult to define the glacier equilibrium line in the glaciers of the northern Japanese Alps.
Furthermore, due to the winter and summer balances of glaciers in the northern Japanese Alps were extremely large, it is considered that the glaciers in the northern Japanese Alps have the highest amount of snowfall and are located in a warm environment among the glaciers in the world.