Water isotopic ratios from a continuously melted ice core sample

Gkinis, Vasileios; Popp, Trevor; Blunier, Thomas; Bigler, Matthias; Schüpbach, Simon; Kettner, Ernesto; Johnsen, S. J.

doi:10.5194/amt-4-2531-2011

Cited by 62 publications

(95 citation statements)

References 38 publications

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“…The CFA system converts ∼ 1 m ice sticks into a continuous liquid water stream, which is then vaporized and analyzed on a CRDS instrument. The full system builds from previous water isotope CFA studies (Gkinis et al, 2010(Gkinis et al, , 2011Maselli et al, 2013;Emanuelsson et al, 2015) and includes novel improvements to the ice delivery mechanism and the melt head. In terms of Allan deviation and response time, the CRDS-CFA system presented here performed similarly to previously published systems from the US, New Zealand, and Denmark (Gkinis et al, 2010(Gkinis et al, , 2011Maselli et al, 2013;Emanuelsson et al, 2015).…”

Section: Discussionmentioning

confidence: 99%

“…Gkinis et al (2011) cite combined measurement uncertainty values of 0.2, 0.06, and 0.5 ‰ for δD, δ 18 O, and dxs, respectively. Maselli et al (2013) and Emanuelsson et al (2015) report similar results.…”

Section: Discussionmentioning

confidence: 99%

“…The flow rate out of the nebulizer is 0.1 m min −1 . Previous CFA isotopic systems have accomplished this step by pumping liquid water through a ∼ 40 µm ID quartz capillary to an aluminium tee split where mixing with dry air and flash vaporization takes place at a temperature of 170 • C (Gkinis et al, 2010(Gkinis et al, , 2011). An advantage of the nebulizer is the wider ID, reducing the susceptibility to clogging from microparticles.…”

Section: Experimental Systemmentioning

confidence: 99%

“…In previous work by Gkinis et al (2010Gkinis et al ( , 2011, a transfer function is fit to an isotopic step change using a scaled version of the cumulative distribution function (CDF) of a normal distribution described by…”

Section: Mixing Length Calculationsmentioning

confidence: 99%

“…The technique, known as continuous-flow analysis (CFA), is accomplished by slowly melting a solid ice stick into a continuous liquid stream, which is then vaporized and injected into the LAS instrument. Gkinis et al (2010Gkinis et al ( , 2011 established the CFA framework for water isotope analysis using LAS. In particular, Gkinis reproduced traditional IRMS water isotope measurements in Greenland ice using a Picarro L1102-i CRDS instrument.…”

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confidence: 99%

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Improved methodologies for continuous-flow analysis of stable water isotopes in ice cores

et al. 2017

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Abstract. Water isotopes in ice cores are used as a climate proxy for local temperature and regional atmospheric circulation as well as evaporative conditions in moisture source regions. Traditional measurements of water isotopes have been achieved using magnetic sector isotope ratio mass spectrometry (IRMS). However, a number of recent studies have shown that laser absorption spectrometry (LAS) performs as well or better than IRMS. The new LAS technology has been combined with continuous-flow analysis (CFA) to improve data density and sample throughput in numerous prior ice coring projects. Here, we present a comparable semiautomated LAS-CFA system for measuring high-resolution water isotopes of ice cores. We outline new methods for partitioning both system precision and mixing length into liquid and vapor components -useful measures for defining and improving the overall performance of the system. Critically, these methods take into account the uncertainty of depth registration that is not present in IRMS nor fully accounted for in other CFA studies. These analyses are achieved using samples from a South Pole firn core, a Greenland ice core, and the West Antarctic Ice Sheet (WAIS) Divide ice core. The measurement system utilizes a 16-position carousel contained in a freezer to consecutively deliver ∼ 1 m × 1.3 cm 2 ice sticks to a temperature-controlled melt head, where the ice is converted to a continuous liquid stream and eventually vaporized using a concentric nebulizer for isotopic analysis. An integrated delivery system for water isotope standards is used for calibration to the Vienna Standard Mean Ocean Water (VSMOW) scale, and depth registration is achieved using a precise overhead laser distance device with an uncertainty of ±0.2 mm. As an added check on the system, we perform inter-lab LAS comparisons using WAIS Divide ice samples, a corroboratory step not taken in prior CFA studies. The overall results are important for substantiating data obtained from LAS-CFA systems, including optimizing liquid and vapor mixing lengths, determining melt rates for ice cores with different accumulation and thinning histories, and removing system-wide mixing effects that are convolved with the natural diffusional signal that results primarily from water molecule diffusion in the firn column.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Experimental Systemmentioning

confidence: 99%

Section: Mixing Length Calculationsmentioning

confidence: 99%

mentioning

confidence: 99%

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Improved methodologies for continuous-flow analysis of stable water isotopes in ice cores

et al. 2017

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Floodplain connection buffers seasonal changes in urban stream water quality

Ledford

Lautz

2014

Hydrological Processes

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Urban streams in the Northeastern United States have large road salt inputs during the winter, increased nonpoint sources of inorganic nitrogen and decreased short‐term and permanent storage of nutrients. Restoration activities that re‐establish connection between streams and riparian environments may be effective for improving urban stream water quality. Meadowbrook Creek, a first‐order stream in Syracuse, NY, provides a unique setting to explore impacts of stream–floodplain connection because it flows along a negative urbanization gradient, from channelized and armoured headwaters to a broad, vegetated floodplain with a riparian aquifer. In this study, we investigated how reconnection to groundwater and introduction of riparian vegetation impacted urban surface water chemistry by making biweekly longitudinal surveys of stream water chemistry in the creek from May 2012 until June 2013. We used multiple methods to measure groundwater discharge rates along the creek. Chloride concentrations in the upstream, disconnected reach were influenced by discharge of road salt during snow melt events and ranged from 161.2 to 1440 mg/l. Chloride concentrations in the downstream, connected reach had less temporal variation, ranging from 252.0 to 1049 mg/l, because of buffering by groundwater discharge, as groundwater chloride concentrations ranged from 84.0 to 655.4 mg/l. In the summer, there was little to no nitrate in the disconnected reach because of limited sources and high primary productivity, but concentrations reached over 1 mg N/l in the connected reach because of the presence of riparian vegetation. During the winter, when temperatures fell below freezing, nitrate concentrations in the disconnected reach increased to 0.58 mg N/l but were still lower than the connected reach, which averaged 0.88 mg N/l. Urban stream restoration projects that restore floodplain connection may impact water quality by storing high salinity road run‐off during winter overbank events and discharging that water year‐round, thereby attenuating seasonal fluctuations in chloride. Contrary to prior findings, we observed that floodplain connection and riparian vegetation may alter nitrate sources and sinks such that nitrate concentrations increase longitudinally in connected urban streams. Copyright © 2014 John Wiley & Sons, Ltd.

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