An open source <scp>B</scp>ayesian <scp>M</scp>onte <scp>C</scp>arlo isotope mixing model with applications in <scp>E</scp>arth surface processes

Arendt, Carli A.; Aciego, S.; Hetland, E. A.

doi:10.1002/2014gc005683

Cited by 36 publications

(42 citation statements)

References 72 publications

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“…The source of distributed system meltwater is largely surface ice and snowmelt and to a lesser extent basal ice melt (Bell, 2008). Hence, δ 2 H and δ 18 O in distributed system meltwater cannot be expected to have the isotopic composition of basal ice as was assumed in and Arendt et al (2015).…”

Section: Source Of Meltwater Runoff Inferred From δ 2 H and δ 18 O Ismentioning

confidence: 93%

Seasonal and interannual variability in the hydrology and geochemistry of an outlet glacier of the Greenland Ice Sheet

Linhoff¹

2016

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Thesis AbstractIn the spring and summer within the ablation zone of the Greenland Ice Sheet (GrIS), meltwater drains to the ice sheet bed through an evolving network of efficient channelized and inefficient distributed drainage systems. Distributed system drainage is a key component in stabilizing GrIS velocity on interannual time scales and controlling geochemical fluxes. During the spring and summer of 2011 and 2012, I conducted fieldwork at a large outlet glacier in southwest Greenland underlain by metamorphic silicate rocks. Data collected from a continuous 222 Rn monitor in the proglacial river were used as a component of a mass balance model. I demonstrated that J dis , the 222 Rn fraction derived from the distributed system, was >90% of the 222 Rn flux on average, and therefore, 222 Rn can be used as a passive flow tracer of distributed system drainage. Supraglacial meltwater runoff estimated using two independent models was compared with ice velocity measurements across the glacier's catchment. Major spikes of J dis occurred after rapid supraglacial meltwater runoff inputs and during the expansion of the subglacial channelized system. While increases in meltwater runoff induced ice acceleration, they also resulted in the formation of efficient subglacial channels and increased drainage from the distributed system, mechanisms known to cause slower late summer to winter velocities. Sr, U, and Ra isotopes and major and trace element chemistry were used to investigate the impact of glacial hydrology on subglacial weathering. Analysis of partial and total digestions of the riverine suspended load (SSL) found that trace carbonates within the silicate watershed largely controlled the 87 Sr/ 86 Sr ratio in the dissolved load. Experiments and sampling transects downstream from the GrIS demonstrated that δ 234 U in the dissolved phase decreased with increasing interaction with the SSL. The ( 228 Ra/ 226 Ra) value of the dissolved load was significantly higher than that of the SSL and therefore, was not the result of the source rock material but of extensive mineral surface weathering and the faster ingrowth rate of 228 Ra (t 1/2 =5.75 y) relative to 226

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Section: Source Of Meltwater Runoff Inferred From δ 2 H and δ 18 O Ismentioning

confidence: 93%

Seasonal and interannual variability in the hydrology and geochemistry of an outlet glacier of the Greenland Ice Sheet

Linhoff¹

2016

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“…End‐member mixing models developed by Thornton and McManus () and further developed by Gordon and Goni () provide a quantitative framework to assess the relative inputs of OC terr and OC mar into marine sediments. These techniques have been furthered by the introduction of Markov chain Monte Carlo (MCMC) methodologies (Li et al, ) and standalone Bayesian isotope mixing models (Arendt et al, ; Morris et al, ). These mixing models use elemental ratios and stable isotope values to separate the terrestrial and marine components; OC terr is isotopically lighter and has a high C:N ratio in comparison to OC mar (Bauer et al, ; Meyers, ; Peter et al, 1978; Redfield et al, ).…”

Section: Methodsmentioning

confidence: 99%

Sources, Sinks, and Subsidies: Terrestrial Carbon Storage in Mid‐latitude Fjords

Smeaton

Austin

2017

JGR Biogeosciences

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Fjords are recognized as globally important sites for the burial and long‐term storage of carbon (C) within sediments. The proximity of fjords to the terrestrial environment in combination with their geomorphology and hydrography results in the fjordic sediments being subsidized with organic carbon (OC) from the terrestrial environment. It has been well documented that terrestrial OC (OCterr) is an important component of coastal sediments, yet our understanding of the quantity of OCterr stored in these sediments remains poorly constrained. Utilizing Bayesian isotopic sediment fingerprinting techniques to the surface sediments of Loch Sunart, we estimate that 42.0 ± 10.1% of the OC is terrestrial in origin. Through combining these outputs with sedimentary OC stock estimates, we have calculated that the surface sediments (0–15 cm) hold 0.1 megaton (Mt) OCterr and estimate that the postglacial sediment held within the fjord contains 3.96 Mt OCterr. When these totals are compared to the quantity of OC stored in the adjacent terrestrial environment, it is clear that the fjord's catchment stores a greater amount of OCterr in the form of vegetation and soil. Though when normalized for area the results suggest that the marine sediments are a more effective long‐term store of OCterr than the adjacent terrestrial environment. This striking result highlights the importance of the terrestrial environment as a source of OC to the coastal ocean and that the OCterr subsidy to the marine sediments is a significant mechanism for the long‐term storage of OC in coastal marine sediments.

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“…The Bayesian Monte Carlo isotope mixing model developed by Arendt et al . [] was used to calculate the mixing ratios of multiple water sources and to quantify the uncertainties caused by variability in the isotopic composition of end‐members and the uncertainties relating to measurement techniques. The method is thoroughly documented in Arendt et al .…”

Section: Methodsmentioning

confidence: 99%

“…The method is thoroughly documented in Arendt et al . [] and briefly presented in supporting information. In practical applications where the detailed uncertainty estimations are usually not indispensable, a simple two‐component mixing model can be used to determine the proportions of summer precipitation and GW in the initial mixture.…”

Section: Methodsmentioning

confidence: 99%

Quantifying spatial groundwater dependence in peatlands through a distributed isotope mass balance approach

Isokangas

Rossi

Ronkanen

et al. 2017

Water Resources Research

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The unique biodiversity and plant composition of peatlands rely on a mix of different water sources: precipitation, runoff, and groundwater (GW). Methods used to delineate areas of ecosystem groundwater dependence, such as vegetation mapping and solute tracer studies, are indirect and lack the potential to assess temporal changes in hydrology, information needed in GW management. This paper outlines a new methodology for mapping groundwater‐dependent areas (GDAs) in peatlands using a 2H and 18O isotope mass balance method. The approach reconstructs the initial isotopic composition of the peat pore water in the uppermost peat layer before its modification by evaporation. It was assumed that pore water in this layer subject to evaporation is a two‐component mixture consisting of GW and precipitation input from the month preceding the sampling period. A Bayesian Monte Carlo isotope mixing model was applied to calculate the proportions of GW and rainwater in the sampled pore water and to assess uncertainties. The approach revealed large spatial variability in the contribution of GW to the pore water present in the top layer of peatland, covering the range from approximately 0 to 100%. Results show that the current GW protection zones determined by Finnish legislation do not cover the GDAs in peatlands and highlight a need for better classification of groundwater‐dependent ecosystems and conceptualization of aquifer‐ecosystem interactions. Our approach offers an efficient tool for mapping GDAs and quantifying the contribution of GW to peatland pore water. However, more studies are needed to test the method for different peatland types.

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An open source Bayesian Monte Carlo isotope mixing model with applications in Earth surface processes

Cited by 36 publications

References 72 publications

Seasonal and interannual variability in the hydrology and geochemistry of an outlet glacier of the Greenland Ice Sheet

Seasonal and interannual variability in the hydrology and geochemistry of an outlet glacier of the Greenland Ice Sheet

Sources, Sinks, and Subsidies: Terrestrial Carbon Storage in Mid‐latitude Fjords

Quantifying spatial groundwater dependence in peatlands through a distributed isotope mass balance approach

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