Physical, chemical, and biological characteristics of supraglacial pools on a debris-covered glacier in Mt. Gongga, Tibetan Plateau

Figures & data

Table 1. Summary of the means (Mn), ranges (Rg), and single values (Sv) of the diameter, surface area, water depth, pH, electrical conductivity, and water temperature of cryoconite holes from glaciers and ice sheets in Svalbard, Greenland, Canada, Italy, Nepal, and Antarctica

Location	Diameter (cm)	Surface area (cm^2)	Water depth (cm)	pH	Electrical conductivity (µS/cm)	Water temperature (°C)
Svalbard^a	Rg: 8.0–12.0	—	—	Sv: 4.6	Sv: 38	Sv: 0.2
Svalbard^b	—	—	Rg: 0.1–49.0	—	—	—
Svalbard^c	—	—	—	Mn: 6.9 Rg: 6.5–7.5	Mn: 21 Rg: 5–53	—
Svalbard^d	—	Mn: 1,287 Rg: 56–31949	Mn: 10.8 Rg: 0.5–27.1	—	—	—
Svalbard^e	—	—	Mn: 5.6 Rg: 3.5–9.0	Mn: 7.9 Rg: 5.8–9.4	Mn: 40 Rg: 7–86	Rg: 0.05–0.22
Greenland^f	Mn: 5.0–7.0	—	Mn: 7.4 Rg: 1.0–16.0	Mn: 5.8 Rg: 4.9–8.2	—	—
Greenland^g	—	Rg: 3–1559	—	—	—	—
Canada^h	Mn: 2.3 Rg: 1.3–4.3	—	—	—	—	—
Canada^i	—	—	—	—	—	Rg: −1.0 to 2.0
Canada^j	Mn: 27.1	Mn: 639	—	Mn: 3.9	Mn: 11	—
Italy^k	Mn: 19.4	—	Mn: 8.4	Mn: 6.2	Mn: 7	—
Nepal^l	Mn: 7.0 Rg: 1.0–36.0	—	Mn: 1.9 Rg: 0.1–6.1	—	—	—
Antarctica^j	Mn: 38.7	Mn: 1,677	—	Mn: 7.9	Mn: 27	—
Antarctica^m	Mn: 22.0–38.0	—	—	Mn: 5.8–8.10	Mn: 60–125	—
Antarctica^n	—	Mn: 777 Rg: 154–4185	—	Mn: 7.0 Rg: 6–10	Mn: 34 Rg: 5–73	—
Antarctica^o	—	Rg: 257.0–729.0	—	—	—	—
Antarctica^p	Rg: 20.0–120.0	—	Rg: 30.0–40.0	Mn: 9.6	—	—
Antarctica^q	—	—	—	—	Rg: 5–21	Rg: −9 to 1.8
Antarctica^r	Mn: 25.8–47.3	—	Mn: 0.0–12.1	Mn: 8.9	—	—
King George Island^s	Mn: 10.0	—	Mn: 15.6	—	—	—

Sources. ^aDe Smet and Van Rompu (1994). ^bVonnahme et al. (2016). ^cZawierucha, Ostrowska et al. (2016). ^dZawierucha, Vonnahme et al. (2016). ^eZawierucha, Buda, and Nawrot (2019). ^fZawierucha et al. (2018). ^gCook et al. (2018). ^hAdams (1966). ⁱMcIntyre (1984). ^jMueller et al. (2001). ^kZawierucha, Buda, Azzoni et al. (2019). ^lTakeuchi et al. (2000). ^mPorazinska et al. (2004). ⁿSommers et al. (2018). ^oDarcy et al. (2018). ^pTranter et al. (2004). ^qBagshaw et al. (2011). ^rTelling et al. (2014). ^sBuda et al. (2020).

Figure 1. (a) Map showing location of Mount Gongga in Tibet, (b) Chinese Gaofen-2 aerial photograph (acquired on 14 May 2015) of Hailuogou Glacier depicting the location of the supraglacial pools sampled (green dots, pools sampled in 2018; yellow dots, pools sampled in 2019), (c) map of Hailuogou Glacier basin and the location of the Mt. Gongga station, (d) and glacier distribution in the Mt. Gongga range, with debris cover shown in gray

Table 2. Mean (SD) of selected environmental variables and macroinvertebrate families in forty-six supraglacial pools within the upper and lower ablation zones on the Hailuogou Glacier in Ganze Tibetan Autonomous Region, China, June 2018 and August 2019

	Upper ablation zone	Lower ablation zone
Environmental variables
Mean LW (cm)	52.92(31.96)a	43.66(21.20)a
Area (cm^2)	4200 (8000)a	2500 (2500)a
Mean water depth (m)	0.47 (0.66)a	0.31 (0.29)a
Mean surface ice to water surface depth (m)	0.20 (0.23)a	0.08 (0.08)a
Number of cryoconite holes within 5 m	0.61 (0.67)a	0.13 (0.35)b
Mean grain size (mm)	11.51 (6.99)a	14.63 (10.20)a
Substrate richness	10.06 (3.18)a	9.93 (3.33)a
Water temperature (°C)	0.80 (1.07)a	0.49 (0.76)a
Conductivity (µS/cm)	21.10 (14.91)a	20.13 (12.50)a
pH	7.86 (0.37)a	7.56 (1.11)a
Macroinvertebrate families
Isotomidae abundance	5.84 (14.97)a	1.53 (2.45)b
Chironomidae abundance	0.55 (0.93)a	1.40 (2.44)a

Note. Different letters within the rows indicate significant differences (p < .05) between the upper and lower ablation zones.

Table 3. Generalized linear model analysis results of the relationships of macroinvertebrate response variables with thirteen physical, chemical, and glacier landscape variables within supraglacial pools on the Hailuogou Glacier, Ganze Tibetan Autonomous Region, China, June 2018 and August 2019

Response variable	Independent variable(s)	Estimate	p
Chironomidae abundance	Water temperature, pH, conductivity, turbidity, mean water depth, surface area, mean ice to water surface depth, distance from north to south boundary, distance to closest pool, number of pools within 5 m, ablation zone, substrate richness, mean grain size	—	>.070
Isotomidae abundance	Water temperature	−1.359	.019
Isotomidae abundance	Conductivity	−120.566	<.001
Isotomidae abundance	Mean ice to water surface depth	3.899	.006
Isotomidae abundance	Number of holes within 5 m	1.122	.009
Isotomidae abundance	Ablation zone	−1.337	.042
Isotomidae abundance	pH, turbidity, mean water depth, surface area, distance from north to south boundary, distance of closest pool, substrate richness, mean grain size	—	>.120
Macroinvertebrate abundance	Conductivity	−99.195	<.001
Macroinvertebrate abundance	Mean ice to water surface depth	3.002	.005
Macroinvertebrate abundance	Number of holes within 5 m	1.041	<.001
Macroinvertebrate abundance	Water temperature, pH, turbidity, mean water depth, surface area, distance from north and south boundaries, distance of closest pool, ablation zone, substrate richness, mean grain size	—	>.110
Chironomidae occurrence	Water temperature, pH, conductivity, turbidity, mean water depth, surface area, mean ice to water surface depth, distance from north to south boundary, distance to closest pool, number of pools within 5 m, ablation zone, substrate richness, mean grain size	—	>.050
Isotomidae occurrence	Conductivity	−156.190	.002
Isotomidae occurrence	Mean water depth	2.042	.046
Isotomidae occurrence	Water temperature, pH, turbidity, surface area, mean ice to water surface depth, distance from north and south boundaries, distance of closest pool, number of pools within 5 m, ablation zone, substrate richness, mean grain size	—	>.090
Macroinvertebrate occurrence	Conductivity	−151.293	.002
Macroinvertebrate occurrence	Water temperature, pH, turbidity, mean water depth, surface area, mean ice to water surface depth, distance from north and south boundaries, distance of closest pool, number of pools within 5 m, ablation zone, substrate richness, mean grain size	—	>.280

Note. Environmental variables that had a significant effect (p < .05) were used within our multimodel inference analyses. Details from the results of environmental variables with nonsignificant results (p < .05) are provided in the Supplementary Material Table S1.

Table 4. Summary of the number of parameters (k), small sample Akaike information criterion (AICc), difference in AICc between each model and the model with the minimum AICc (ΔAICc), Akaike weight (Wi), and percentage deviance (%Dev) from the three best models of the generalized linear model analyses of Isotomidae abundance, macroinvertebrate abundance, Isotomidae occurrence selected environmental predictors within supraglacial pools on the Hailuogou Glacier, Ganze Tibetan Autonomous Region, China, June 2018 and August 2019

Response variable	Independent variable	k	AICc	ΔAICc	Wi	%Dev
Isotomidae abundance	C, IWSD	2	189.32	0.00	0.18	43.01
Isotomidae abundance	WT, C, IWSD	3	190.18	0.86	0.12	45.29
Isotomidae abundance	C, NP5M	2	190.56	1.25	0.10	41.07
Macroinvertebrate abundance	C, NP5M	2	216.70	0.00	0.62	50.70
Macroinvertebrate abundance	C, NP5M, IWSD	3	218.45	1.75	0.26	51.78
Macroinvertebrate abundance	C, IWSD	2	220.51	3.81	0.09	0.00
Isotomidae occurrence	C, MWD	2	48.08	0.00	0.53	34.91
Isotomidae occurrence	C	1	48.32	0.24	0.47	30.93
Isotomidae occurrence	MWD	1	61.61	13.53	0.00	10.09

Notes. Additional details from the results of twenty-four additional Isotomidae abundance models and four macroinvertebrate abundance models are available in the Supplementary Materials Table S2. C = conductivity; IWSD = mean ice to water surface depth; WT = water temperature; NH5M = number of pools within 5 m; MWD = mean water depth.

Figure 2. Predicted relationships between (a) Isotomidae occurrence and conductivity, (b) macroinvertebrate occurrence and conductivity, (c) Isotomidae abundance and conductivity, (d) Isotomidae abundance and mean ice to water surface depth, (e) macroinvertebrate abundance and conductivity, and (f) macroinvertebrate abundance and number of supraglacial pools within 5 m within supraglacial pools on the Hailuogou Glacier, Ganze Tibetan Autonomous Region, China, June 2018 and August 2019

Figure 3. Photographs of Hailuogou Glacier supraglacial pools that depict the various shapes and different ice surface–to–water depths observed. Some supraglacial pools had (a), (d) water located at the surface of the ice and others had (b), (e) water levels below the surface of the glacier ice. (c) The genesis of a pool was captured in the upper zone of the ablation tongue. (f) Typical sediment sampled in a supraglacial pool, (g) sediment precipitously positioned on ice above a pool, and (h) the formation of a pool at the base of a small crevasse. The velocity meter in the images is 1.14 m long

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