Publisher Correction: Seismic ground vibrations give advanced early-warning of subglacial floods.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Seismic ground vibrations give advanced early-warning of subglacial floods.

Glacier runoff and melt from volcanic and geothermal activity accumulates in glacier dammed lakes in glaciated areas around the world. These lakes eventually drain, creating hazardous subglacial floods that are usually only confirmed after they exit the glacier and reach local river systems, which can be many tens of kilometres from the flood source. Once in the river systems, they travel rapidly to populated areas. Such delayed detection represents a potentially lethal shortcoming in early-warning. Here we demonstrate how to advance early-warning potential through the analysis of four such floods in a glaciated region of Iceland. By comparing exceptional multidisciplinary hydrological, GPS and seismic ground vibration (tremor) data, we show that array analysis of seismic tremor can be used for early location and tracking of the subglacial flood front. Furthermore the timing and size of the impending flood can be estimated, prior to it entering the river system. Advanced warnings of between 20 to 34 hours are achieved for large (peak discharge of more than 3000 m3/s, accumulation time of ~ 5.25 years) to small floods (peak discharges from 210 to 380 m3/s, accumulation times of ~ 1.3 years) respectively.

Microbial communities in the subglacial waters of the Vatnajökull ice cap, Iceland.

Subglacial lakes beneath the Vatnajökull ice cap in Iceland host endemic communities of microorganisms adapted to cold, dark and nutrient-poor waters, but the mechanisms by which these microbes disseminate under the ice and colonize these lakes are unknown. We present new data on this subglacial microbiome generated from samples of two subglacial lakes, a subglacial flood and a lake that was formerly subglacial but now partly exposed to the atmosphere. These data include parallel 16S rRNA gene amplicon libraries constructed using novel primers that span the v3-v5 and v4-v6 hypervariable regions. Archaea were not detected in either subglacial lake, and the communities are dominated by only five bacterial taxa. Our paired libraries are highly concordant for the most abundant taxa, but estimates of diversity (abundance-based coverage estimator) in the v4-v6 libraries are 3-8 times higher than in corresponding v3-v5 libraries. The dominant taxa are closely related to cultivated anaerobes and microaerobes, and may occupy unique metabolic niches in a chemoautolithotrophic ecosystem. The populations of the major taxa in the subglacial lakes are indistinguishable (>99% sequence identity), despite separation by 6 km and an ice divide; one taxon is ubiquitous in our Vatnajökull samples. We propose that the glacial bed is connected through an aquifer in the underlying permeable basalt, and these subglacial lakes are colonized from a deeper, subterranean microbiome.