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Melting glaciers: Hidden hazards

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Science  05 May 2017:
Vol. 356, Issue 6337, pp. 495
DOI: 10.1126/science.aan4118

Chemicals released from melting glaciers can pollute local habitats.

PHOTO: DIEGOGRANDI/ISTOCK PHOTO

In her In Depth News story “Chile's glacial lakes pose newly recognized flood threat” (10 March, p. 1004), J. Palmer did not mention that melting glaciers pose risks beyond flooding. The water itself contains hidden hazards.

Melting glaciers can release nutrients and pollutants into glacial rivers, which further erode watersheds and contaminate downstream environments. Polar ice sheets may export substantial quantities of iron (1, 2), which affects coastal ecosystems (3, 4). European alpine glaciers have been shown to contain chemicals introduced in the past by humans, which drain into lakes when the ice melts (5). Melting Himalayan glaciers contribute persistent organic pollutants to the surface waters in the nearby Gangetic Plain during the dry season (6). Glaciers in the inland Tibetan Plateau discharge toxic mercury (7). Increased meltwater due to warming temperatures and extreme rainfall could lead to greater glacial river discharge, which would be able to detach and transport higher levels of these chemicals. The timing of such glacial runoff often coincides with biomass blooms (8), magnifying the cumulative risk to the environment.

Glacial lake flooding could cause acute damage to local habitats and inhabitants, but the contaminated water of glacial rivers could have lasting and latent effects on distant environments. These risks should be included in the assessment and mitigation of glacial disasters.

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