A high resolution glacier model with debris effects in Bhutan Himalaya. Orie SASAKI Kanae Laboratory 2018/02/08 (Thu)

Transcription

1 A high resolution glacier model with debris effects in Bhutan Himalaya Orie SASAKI Kanae Laboratory 2018/02/08 (Thu)

2 Research flow Multiple climate data at high elevations Precipitation, air temperature and etc. 2 Initial glacier data Case1 Temperature index glacier model Case2 Energy balance glacier model with debris effect Runoff from glaciers (Case1,2) Hydrological model River discharge (Case1,2)

3 Research flow Multiple climate data at high elevations Precipitation, air temperature and etc. 3 Initial glacier data Case1 Temperature index glacier model Case2 Energy balance glacier model with debris effect Runoff from glaciers (Case1,2) Hydrological model River discharge (Case1,2)

4 Energy Balance Model 4 Shortwave Radiation Longwave Radiation Latent heat flux Sensible heat flux Debris Effects Energy Flux for Melting

5 Debris on Glaciers 5 No Debris Debris covered glacier Debris :sand gravel, rocks Supraglacial debris affects glacier melting rate significantly. (e.g. Mattson et al.,1993) Ex) Rocks inhibits ice melting (Photo: Florian Mair, 2010)

6 Debris on Glaciers Effects of debris on glacier melts 6 No Debris Albedo is high Thin Debris Albedo become low Thick Debris Heat insulation effect melt Glacier melt Glacier melt Glacier Accelerate Suppress Debris thickness is important! Clean ice Melting rate Accelerate Same as clean ice Suppress Thin intermediate Thick Debris thickness

7 Energy Balance Model 7 Shortwave Radiation Longwave Radiation Latent heat flux Sensible heat flux Debris Effects Energy Flux for Melting Objective Estimating glacier melts by a glacier model based on energy balance with debris effects 1.Development of debris information data 2.Model structure

8 8 1. Development of debris information data

9 Necessary parameters 9 Debris Glacier? To estimate debris effect, Thickness [m] Thermal conductivity [Wm -1 K -1 ] Ground observation is the only way (Zhang et al., 2011) It is unrealistic to measure these parameters on a large scale.

10 How to get necessary 10 parameters Debris Glacier? Thermal resistance (TR) of debris layer [m 2 K W -1 ] TR = debris thickness thermal conductivity (Nakawo and Young, 1981, 1982) TR can be estimated from Satellite Data. Photo: NASA Photo: NASA

11 Previous study 11 Some studies estimated thermal resistance of debris from satellite data. Target Region Number of satellite images Suzuki et al., 2007 Lunana region 11 Zhang et al., 2011 Hailugou glacier 2 Fujita et al., 2014 Trambau glacier 8 Distribution of thermal resistance on debris at Trambau glacier (Fujita et al., 2014) Estimate distribution of thermal resistance of debris on Bhutan Glaciers

12 Data for analysis 12 Details Data Data Spatial Res. Time Res. Period Landsat 8 ERA-Interim AW3D30 Band 2~7 30m 16 days Band 10 (TIR) 100m 16 days Reanalysis data (Radiation, Air temp, Humidity, Wind speed) Elevation data (ALOS PRISM) hourly m ーー RGI 6.0 Glacier Outline data Vector ーー

13 Data for analysis 13 Details Data Data Spatial Res. Time Res. Period Landsat 8 ERA-Interim AW3D30 Band 2~7 30m 16 days Band 10 (TIR) 100m 16 days Reanalysis data (Radiation, Air temp, Humidity, Wind speed) Earth Observation Satellite Landsat 8 Elevation data (ALOS PRISM) Multi-temporal 208 data set hourly m ー ー RGI 6.0 Glacier Outline data Vector ーー Photo: NASA (Landsat, 2013/11/13)

14 Data for analysis 14 Details Data Data Spatial Res. Time Res. Period Landsat 8 ERA-Interim AW3D30 Band 2~7 30m 16 days Band 10 (TIR) 100m 16 days Reanalysis data (Radiation, Air temp, Humidity, Wind speed) Elevation data (ALOS PRISM) ERA-Interim : hourly m ーー Reanalysis climate data by ECMWF RGI 6.0 Glacier Outline data Vector ーー Downward shortwave and longwave radiation Air temperature Relative humidity Wind speed (Fig. from ERA-Interim Web page)

15 Data for analysis 15 Details Data Data Spatial Res. Time Res. Period Landsat 8 ERA-Interim AW3D30 Band 2~7 30m 16 days Band 10 (TIR) 100m 16 days Reanalysis data (Radiation, Air temp, Humidity, Wind speed) AW3D30: ALOS World 3D - 30m Elevation Data (30m resolution) Elevation data (ALOS PRISM) hourly Multi-temporal 208 data sets 30m ーー RGI 6.0 Glacier Outline data Vector ーー 7500m 3500m Photo: JAXA ALOS PRISM (JAXA)

16 Data for analysis 16 Details Data Data Spatial Res. Time Res. Period Landsat 8 Band 2~7 30m 16 days Band 10 (TIR) 100m 16 days ERA-Interim AW3D30 Reanalysis data (Radiation, Air temp, Humidity, Wind speed) Elevation data (ALOS PRISM) hourly Multi-temporal 208 data sets 30m ーー RGI 6.0 Glacier Outline data Vector ーー

17 Calculation of TR 17 Thermal Resistance (TR) [m 2 K W -1 ] Surface temp. Assumption (2) Linear temperature profile in debris Melting temp. Assumption (1) Melting condition Remote sensing TR = T s T i Q g = T s T i R n + LE + H Q g :Heat flux into glacier [Wm -2 ] R n LE H :Net Radiation [Wm -2 ] :Latent heat flux [Wm -2 ] :Sensible heat flux [Wm -2 ] Remote sensing Remote Sensing + Reanalysis data

18 Flow of calculation Data Set 208 Data Set 3 Data Set 2 Data Set 1 Albedo Landsat 8 Band 2, 4~7, 10 Surface Temperature AW3D30 (Elevation Data) Climate data (Downward radiation, Air temp., Wind speed, Relative humidity) 18 Latent Heat/Sensible Heat Flux Net Radiation Thermal Resistance Wide-area Map of Thermal Resistance RGI 6.0 Outline of Glaciers 208 data Thermal Resistance on glaciers 90m-resolution

19 Flow of calculation 19 1 TR 2Large area map of TR No. 208 No. 3 No. 2 No. 1 Eliminate cloud/snow Glacier Outline Thermal Resistance [Km 2 /W] 3Extract glacier area 90m resolution distribution map of thermal resistance

20 20 How to eliminate cloud and snow 1 Cloud and snow makes TR lower select maximum value 2 Interannual variation can be neglected Thermal Resistance (m 2 K W -1 )

21 Results 21 Clean Thin Thermal Resistance ( 10-2 m 2 K W -1 ) > 7 Thick Google Map

22 Results 22 Clean Thin Thermal Resistance ( 10-2 m 2 K W -1 ) > 7 Thick Classification Clean ice Debris Glacial ponds Google Map Classification by Landsat 8 (Kraaijenbrink et al., 2017)

23 Results 23 Clean Thin Thermal Resistance ( 10-2 m 2 K W -1 ) > 7 Thick Classification Clean ice Debris Glacial ponds Several large glaciers has much debris. There are small patches which has erroneous high TR value. (should be corrected) Google Map

24 2. Model Structure 24

25 Base Model 25 Glacier Model by Fujita et al., 2014 (Fujita model) Developed for Trambau glacier (located in Nepal Himalaya) Energy Balance Model with Debris effect

26 Base Model 26 Glacier Model by Fujita et al., 2014 (Fujita model) Developed for Trambau glacier (located in Nepal Himalaya) Energy Balance Model with Debris effect Glacier area is divided into (i) Clean ice and (ii) Debris-covered ice. By using Landsat data (Kraaijenbrink et al., 2017) (i) Clean ice Thermal Resistance 90m res. (ii) Debris-covered ice

27 Model Structure Mass balance was calculated in clean ice part and debris-covered part separately. 27 (i) Clean ice (ii) Debris-covered ice 50m elevation band Each grid is sorted into 50m elevation band. Mass balance was calculated in each band. 90m 90m grid Mass balance was calculated in each 90m grid.

28 Model Structure 28 Thermal Resistance, Albedo (90 m resolution) Snow albedo Newly Developed Climate data (0.5 resolution) Snow fall Energy Balance Model Clean ice Debris-covered ice One year after snowfall Glacier ice 50m elevation band 90m 90m grid Melting Accumulation Mass Balance Runoff

29 Glacier area evolution 29 Area change is calculated from mass change. Step 1. Initial value Initial area A 0 : from RGI6.0 Initial volume V 0 : V 0 = c v A 0 γ (Volume-Area scaling, Bliss et al., 2013) Parameters Mountain glaciers: c v = m 3 2γ, γ = Ice caps: c v = m 3 2γ, γ = Step 2. Calculation of mass balance Mass balance B i : calculated for each grid(debris) or elevation band(clean ice) Repeat for N years Step 3. Set new area and volume V t = V t 1 + 1Τρ ice σ n i=1 B i A i A t = V t Τc 1Τγ v Parameters ρ ice : Density of ice = 900 kgm 3

30 Calibration method 30 Local Local model Calibration by using ground observation data of each glacier Large scale Global Glacier Models (~2015) Extrapolating limited direct observation data (Radic and Hock, 2011; Radic et al., 2013; Hirabayashi et al., 2010, 2013; Marzeion et al., 2012; Bliss et al., 2014) Global Glacier Model (Huss et al., 2015) Extrapolating is problematic. Direct observation data is restricted to rather small glaciers Each individual glacier s mass balance M g is assumed to be same as the average regional mass balance M reg M g = M reg

31 Calibration Flow 31 Calibration method: M g = M reg M reg : Average regional mass balance in whole Asia ( ) (Gardner et al., 2013) Observation data of Bhutan glacier will improve model performance. Calibration period: Model Simulation ( ) c prec Adjustment of precipitation T air Adjustment of temperature Repeat Calibration parameters: c prec : Precipitation ratio [%] (0.8<c prec <2.0) T air : Air temperature [ ] M g = M reg? Yes No M g = M reg? No Initial value: c prec = 1.0, T air = 0.0 Final parameter set Yes

32 Model Structure 32 Thermal Resistance, Albedo (90 m resolution) Snow albedo Newly Developed Climate data (0.5 resolution) Snow fall New Glacier Area Volume Energy Balance Model Clean ice Debris-covered ice One year after snowfall Glacier ice 50m elevation band 90m 90m grid Melting Accumulation Volume-Area scaling Mass Balance Runoff

33 Research flow Multiple climate data at high elevations Precipitation, air temperature and etc. 33 Initial glacier data Case1 Temperature index glacier model Case2 Energy balance glacier model with debris effect Runoff from glaciers (Case1,2) Hydrological model River discharge (Case1,2)

34 River Discharge (H08) 34 Runoff from Glaciers (Case1, Case2) Input Input Newly Developed Climate data Crop growth Water withdrawal Env. water Reservoir operation Virtual water Model H08 Output River discharge (Case1, Case2) Land surface River (Hanasaki et al., 2008) Consisted of 7 modules Use 2 modules River Land surface Two type of river discharge will be obtained. (from case1 & case2) Uncertainty range

35 Summary 35 The distribution of thermal resistance of debris on glaciers has been detected in Bhutan by using remote-sensing data. A glacier model with energy balance and debris effects was developed. Observation data of Bhutan glaciers will improve model performance. Next Steps Historical and future simulation of glacier runoff for all glaciers in Bhutan (Glacier model). Simulation of river discharge including the effects of glacier melts (H08). Thank you for your kind attention