Quantifying Meltwater Sources and Contaminant Fluxes from the Athabasca Glacier, Canada

Abstract

Glaciers are retreating across the Canadian Rocky Mountains. As this ice volume is lost, trace elements, nutrients, and other contaminants, accumulated from millennia of atmospheric deposition, are subject to release in glacier meltwater with uncertain consequences for downstream water quality. We monitored and modeled meltwater chemistry at a high temporal resolution using a combination of grab sampling and sondes at the mouth of proglacial Sunwapta River, which drains the Athabasca Glacier in the Canadian Rocky Mountains. Two chemically and temporally distinct sources to melt were distinguished by principal component analysis: a component with a long subglacial residence time characterized by dissolved carbonate-associated elements, and a supra- and englacial component with short subglacial residence time, which contained potential legacy trace elements at low total concentrations and predominantly in a particulate form (total mercury, <3.2 ng/L; total lead, arsenic, and chromium, <2.0 μg/L) and legacy nutrients at moderate concentrations (nitrogen, <0.22 mg/L; phosphorus, <0.03 mg/L). Trace element fluxes and yields were modeled by pairing grab sampling results with correlated high-frequency conductivity or turbidity. Mercury yield (3.2 g/year/km2) was comparable to or lower than yields from other glacial meltwater streams globally. Long-term discharge data suggests that future contaminant yields will increase until peak water is reached, but at present, glacial meltwater does not significantly augment downstream nutrient and trace element contaminant budgets.

A preliminary investigation of microbial communities on the Athabasca Glacier within deposited organic matter

“…77 Glacier samples from this study all had relatively similar total dissolved phosphorus (TDP), with ice having the greatest (85.7 ± 94.9 µg L −1 ), surface sediment having the lowest (54.7 µg L −1 ), and cryoconite holes having a value of 67.5 µg L −1 . Previously analyzed grab samples of meltwater from the Athabasca Glacier contained lesser concentrations of total phosphorus of 16 ± 10 µg L −1 , 32 suggesting dilution by precipitation and early-season snowmelt. TDP concentrations detected in collected samples were exceptionally high when compared to total phosphorus (TP) in ice samples from the two Svalbard glaciers (0.11–0.14 mg L −1 ).…”

Anthropogenic contaminants in glacial environments I: Inputs and accumulation

“…These microorganisms can also accelerate the decomposition of metal ions into toxic and more bioavailable forms, such as mercury into methylmercury by sulphur-reducing microbes (St. Pierre et al, 2019; Staniszewska et al, 2021). This makes cryoconite very efficient at storing potentially toxic contaminants, which may result in negative downstream effects on glacier-fed ecosystems under climate warming scenarios (Hodson et al, 2010).…”

“…These mechanisms can create concentrated pockets of contaminant-rich sediment in the lower parts of glaciers, which could be environmentally harmful if released in a short period of time. This may also decrease downstream water quality through the amplification of sedimentary budgets and the increase of sediment and contaminant loads under future melt (Staniszewska et al, 2021).…”

“…Similarly, the filamentous morphology and sticky nature of microorganisms that live on cryoconite, such as extremophiles, cyanobacteria and microbes, helps cryoconite to entangle debris and contaminants within the sediment (Cook et al, 2016;Huang et al, 2019;Pittino et al, 2018). These microorganisms can also accelerate the decomposition of metal ions into toxic and more bioavailable forms, such as mercury into methylmercury by sulphur-reducing microbes (St. Pierre et al, 2019;Staniszewska et al, 2021). This makes cryoconite very efficient at storing potentially toxic contaminants, which may result in negative downstream effects on glacier-fed ecosystems under climate warming scenarios (Hodson et al, 2010).…”

Size-Resolved Fluorescence Underscores Negligible Interaction of Dissolved Organic Matter During Conservative Mixing in a Large Boreal River

“…From there, its waters move into the Mackenzie River and ultimately into the Arctic Ocean. Along the river, the concentration of dissolved organic carbon (DOC) increases over nine-fold from 1.0 mg C L −1 in the Athabasca Glacial meltwater (flow rate: ≤ 14 m 3 /s) to 9.4 mg C L −1 in waters collected from the lower reach of the AR (i.e., LAR; flow rate: ~450-700 m 3 /s) (Staniszewska et al, 2021;Xue et al, 2022). Under base-flow conditions, such a longitudinal increase of DOC is largely contributed by major tributaries (Cuss et al, 2019).…”