Identifying weathering sources and processes in an outlet glacier of the Greenland Ice Sheet using Ca and Sr isotope ratios

Hindshaw, Ruth S.; Rickli, Jörg; Leuthold, Julien; Wadham, Jemma L.; Bourdon, Bernard

doi:10.1016/j.gca.2014.09.016

Cited by 54 publications

(101 citation statements)

References 108 publications

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“…On the south side of Leverett Glacier's snout, the bedrock is a late Achaean (2.5 Ga) granite (Escher, 1971;Nutman et al, 2010) while the Ikertoq complex (1.85 Ga), composed of basement gneisses and granites, borders the north side (Henriksen et al, 2009). The proglacial valley is filled with quaternary sediments composed of weathered materials from afore mentioned rock units (Hindshaw et al, 2014). This suggests that the subglacial lithology is similar to the bedrock adjacent to the glacier's snout.…”

Section: Study Areamentioning

confidence: 99%

Utility of 222Rn as a passive tracer of subglacial distributed system drainage

Linhoff

Charette

Nienow

et al. 2017

Earth and Planetary Science Letters

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Keywords: radon Greenland glacier proglacial river meltwater Water flow beneath the Greenland Ice Sheet (GrIS) has been shown to include slow-inefficient (distributed) and fast-efficient (channelized) drainage systems, in response to meltwater delivery to the bed via both moulins and surface lake drainage. This partitioning between channelized and distributed drainage systems is difficult to quantify yet it plays an important role in bulk meltwater chemistry and glacial velocity, and thus subglacial erosion. Radon-222, which is continuously produced via the decay of 226 Ra, accumulates in meltwater that has interacted with rock and sediment. Hence, elevated concentrations of 222 Rn should be indicative of meltwater that has flowed through a distributed drainage system network. In the spring and summer of 2011 and 2012, we made hourly 222 Rn measurements in the proglacial river of a large outlet glacier of the GrIS (Leverett Glacier, SW Greenland). Radon-222 activities were highest in the early melt season (10-15 dpm L −1 ), decreasing by a factor of 2-5 (3-5 dpm L −1 ) following the onset of widespread surface melt. Using a 222 Rn mass balance model, we estimate that, on average, greater than 90% of the river 222 Rn was sourced from distributed system meltwater. The distributed system 222 Rn flux varied on diurnal, weekly, and seasonal time scales with highest fluxes generally occurring on the falling limb of the hydrograph and during expansion of the channelized drainage system. Using laboratory based estimates of distributed system 222 Rn, the distributed system water flux generally ranged between 1-5% of the total proglacial river discharge for both seasons. This study provides a promising new method for hydrograph separation in glacial watersheds and for estimating the timing and magnitude of distributed system fluxes expelled at ice sheet margins. Published by Elsevier B.V.

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Section: Study Areamentioning

confidence: 99%

Utility of 222Rn as a passive tracer of subglacial distributed system drainage

Linhoff

Charette

Nienow

et al. 2017

Earth and Planetary Science Letters

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“…627 6a). Titanite enrichments in catchment sediments relative to Ro4 are 628 supported by elevated Ti concentrations (Hindshaw et al, 2014). Smaller 629 effects in Nd isotope compositions are also modelled for garnet (~ 0.4 εNd for 4 630 wt.%) and apatite (~ 1 εNd for 0.2 wt.%) addition.…”

Section: Hafnium and Neodymium In Sediments 619mentioning

confidence: 96%

“…Major 312 elements -Si, Al, Fe, Ti, Ca, Mg, K, Na, P, Mn -and Sr concentrations for these 313 fused samples were presented in Hindshaw et al (2014). Fusion will 314 completely dissolve highly resistant minerals like zircon, whereas they can 315 remain largely unaffected during hotplate digestion.…”

Section: Elemental Concentrations Of Hf Sm and Nd 304mentioning

confidence: 99%

“…1b) were also analysed for trace elements by LA-ICP-MS 318 using a Thermo Element XR connected to a 193 nm Resonetics ArF Excimer 319 laser (ETH Zurich). Some of these sediments were collected from the same 320 sites as in Hindshaw et al (2014), although they represent separate sample 321 aliquots. Coordinates of sampling locations and further details are given in 322 Appendix S1.…”

Section: Elemental Concentrations Of Hf Sm and Nd 304mentioning

confidence: 99%

“…The major element composition of catchment sediments and their plagioclase 620 grains suggests large contributions from grey relative to pink orthogneisses 621 and amphibolites (Hindshaw et al, 2014). The catchment sediments can, 622 hence, be modelled as Ro4 complemented with additional minerals like garnet 623 and hornblende at their observed abundance in sediments (Table 3).…”

Section: Hafnium and Neodymium In Sediments 619mentioning

confidence: 99%

See 2 more Smart Citations

Impact of glacial activity on the weathering of Hf isotopes – Observations from Southwest Greenland

Rickli

Hindshaw

Leuthold

et al. 2017

Geochimica et Cosmochimica Acta

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Carbon dating reveals a seasonal progression in the source of particulate organic carbon exported from the Greenland Ice Sheet

Kohler

Žárský

Yde

et al. 2017

Geophysical Research Letters

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Surface melt from the Greenland Ice Sheet (GrIS) collects particulate organic carbon (POC) as it drains into subglacial environments and transports it downstream where it serves as a microbial substrate. We hypothesized that older POC is entrained by meltwaters as the subglacial drainage network expands upglacier over the summer. To test this, POC samples were collected from a meltwater river exiting the GrIS over an ablation season and 14C dated. Resulting values were compared with meltwater hydrochemistry and satellite observations of the catchment area. We found that POC ages increased from ~5000 to ~9000 years B.P. until peak discharge and catchment size. Afterward, significant fluctuations in POC age were observed, interpreted to result from periods of high and low subglacial hydrological pressure and sediment supply and subsequent exhaustion. These observations suggest a seasonal progression in the source of POC exported from the GrIS and provide evidence for a seasonally evolving subglacial drainage system.

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Identifying weathering sources and processes in an outlet glacier of the Greenland Ice Sheet using Ca and Sr isotope ratios

Cited by 54 publications

References 108 publications

Utility of 222Rn as a passive tracer of subglacial distributed system drainage

Utility of 222Rn as a passive tracer of subglacial distributed system drainage

Impact of glacial activity on the weathering of Hf isotopes – Observations from Southwest Greenland

Carbon dating reveals a seasonal progression in the source of particulate organic carbon exported from the Greenland Ice Sheet

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