Mass balance of two perennial snowfields: Niwot Ridge, Colorado, and the Ulaan Taiga, Mongolia

Figures & data

Figure 1. Arapaho Glacier, taken 27 August 1960. Site map of the Arapaho Glacier in Colorado, indicated by the red X, coordinates 40°01′24″ N 105°38′53″ W, elevation 3,680 m. The distance across the snowfield is about 600 m. The D1 site is also located at the red X, being less than 1 km from the glacier, and is therefore not shown at this scale. Neighboring states of Utah (UT), Wyoming (WY), Nebraska (NE), Arizona (AZ), New Mexico (NM), Oklahoma (OK), and Kansas (KS) are indicated. Image credit: Henry Waldrop, 1960. Arapaho Glacier: From the Glacier Photograph Collection. Boulder, Colorado: National Snow and Ice Data Center. Digital media. Source: http://nsidc.org/data/glacier_photo/search/image_info/arapaho_waldrop_084.

Figure 2. (a) Hourly measurements of air temperature (°C) and relative humidity (RH, %) for the Niwot Ridge data set, used to drive the Arapaho Glacier perennial snowfield model. T_air is the air temperature. (b) Wind speed and precipitation rate.

Figure 3. Site map of the perennial snowfields in Mongolia, coordinates 51°10′45″ N 98°58′06″ E, elevation 2,243 m. The red X marks the general location of the snowfields from Taylor et al. (2019). Insert A shows a snowfield that appears to be a river icing and a smaller snowfield (B) that appears to be on the shore of the stream. These snowfields are close to, perhaps identical to, Site 3 from Taylor et al. (2019). North is upward in the insert. Digital Globe Image was taken on 15 July 2015 and provided to the National Aeronautics and Space Admininstration with no restrictions on use or copying.

Figure 4. (a) Hourly measurements of air temperature (°C) and relative humidity (%) used to drive the Ulaan Taiga perennial snowfield model. T_air is the air temperature. (b) Wind speed and precipitation rate.

Table 1. Base case model parameters for Ulaan Taiga, Mongolia, and Arapaho Glacier, Colorado. These parameters are later varied in order to determine model sensitivities.

Parameter	Mongolia	Arapaho Glacier
Slope angle	0°	30°
Aspect	N/A	90 (clockwise from north)
Initial dust content of snow	1,000 ppm	1,000 ppm
Snow density	500 kg/m^3	500 kg/m^3
Snow grain diameter	120 microns	120 microns
Ground (substrate) density	1400 kg/m^3	1400 kg/m^3
Ground thermal conductivity	0.25 W m^−1 K^−1	0.25 W m^−1 K^−1

Figure 5. Sensitivity of the snow column mass balance to experiments for the Arapaho Glacier case where the initial modeled snow depth is 4.5 m. “C. Warming” and “N. Warming” refer to constant warming and nighttime warming scenarios, respectively.

Figure 6. Sensitivity of the snow column mass balance to experiments for the Ulaan Taiga, Mongolia, case where the initial modeled snow depth is 4.5 m. “C. Warming” and “N. Warming” refer to constant warming and nighttime warming scenarios, respectively.

Figure 7. Change in modeled snowpack lifetime for the 1.0-m Arapaho Glacier cases. The base case lifetime for 1-m snowpack was 247 days. As explained in the text, the wind case survived for an entire year and is therefore plotted as 48 percent longer than the base case lifetime. “C. Warming” and “N. Warming” refer to constant warming and nighttime warming scenarios, respectively.

Figure 8. Change in modeled snowpack lifetime for the 1.0-m cases for Ulaan Taiga, Mongolia, experiments. The base case lifetime for a 1-m snowpack was 221 days. “C. Warming” and “N. Warming” refer to constant warming and nighttime warming scenarios, respectively.

Figure 9. Model sensitivity test analysis for the Arapaho Glacier 4.5-m case. Note change of scale relative to Figures 5 to 8.

Figure 10. Total snowpack ablation amounts due to sublimation and melting for both snowfields in both locations. The amounts are shown for the base case. The Arapaho Glacier and Mongolia experiments were conducted with a 4.5-m snowpack.

Table

Experiments—Arapaho Glacier	Start mass (kg)	End mass (kg)	Change (%)
Base case	2,347.6	2,345.7	−0.08
Constant warming (2°C)	2,347.6	1,277.0	−45.60
Nighttime warming (0.25°C)	2,347.6	2,274.1	−3.13
Precipitation increase (1.22 times)	2,347.6	2,762.4	17.67
Wind decrease (0.82)	2,347.6	3,499.8	49.08
Dust increase (2 times)	2,347.6	2,295.5	−2.22

Table

Experiments—Mongolia	Start mass (kg)	End mass (kg)	Change (%)
Base case	2,347.6	2,348.7	0.05
Constant warming (2°C)	2,347.6	1,452.8	−38.12
Nighttime warming (0.25°C)	2,347.6	2,307.5	−1.71
Precipitation increase (1.22 times)	2,347.6	2,430.1	3.51
Wind decrease (0.74)	2,347.6	3,161.3	34.66
Dust increase (2 times)	2,347.6	2,339.9	−0.33

Table

Experiments—Arapaho Glacier	Start mass (kg) or base case lifetime	End mass (kg) or lifetime	Change (%)
Base case	247 days	247 days	0.00
Constant warming (2°C)	247 days	224 days	−0.09
Nighttime warming (0.25°C)	247 days	244 days	−0.01
Precipitation increase (1.22 times)	247 days	270 days	0.09
Wind decrease (0.82)	504.5 kg	1,574.8 kg	212.12
Dust increase (2 times)	247 days	245 days	−0.01

Table

Experiments—Mongolia	Start mass (kg) or base case lifetime	End mass (kg) or lifetime	Change (%)
Base case	221 days	221 days	0.00
Constant warming (2°C)	221 days	207 days	−0.06
Nighttime warming (0.25°C)	221 days	220 days	0.00
Precipitation increase (1.22 times)	221 days	223 days	0.01
Wind decrease (0.74)	221 days	239 days	0.08
Dust increase (2 times)	221 days	221 days	0.00

Table

Sensitivity tests—Arapaho Glacier	Start mass (kg)	End mass (kg)	Change (%)
Slope 30° to >20°	2,347.6	2,366.7	0.82
Aspect 90° to >100°	2,347.6	2,285.5	−2.65
Aspect 90° to >80°	2,347.6	2,407.3	2.54
Snow density 500 to >400 kg/m^3	1,922.0	1,970.1	2.50
Initial dust 1000 to >100 ppm	2,349.7	2,523.9	7.42
Ground density 1400 to >1600 kg/m^3	2,347.6	2,345.6	−0.08
Snow grain diameter 120 to >180 μm	2,347.6	2,239.3	−4.61
k_prime_ground 0.25 to >0.35 w/mK	2,347.6	2,345.5	−0.09

Taylor, W., J. K. Clark, B. Reichhardt, G. W. L. Hodgins, J. Bayarsaikhan, O. Batchuluun, J. Whitworth, M. Nansalmaa, C. M. Lee, E. J. Dixon, et al. 2019. Investigating reindeer pastoralism and exploitation of high mountain zones in northern Mongolia through ice patch archaeology. PLoS ONE 14 (11):e0224741. doi:10.1371/journal.pone.0224741.

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