A laser fluorination method for oxygen isotope analysis of biogenic silica and a new oxygen isotope calibration of modern diatoms in freshwater environments

Dodd, J. P.; Sharp, Zachary D.

doi:10.1016/j.gca.2009.11.023

Cited by 85 publications

(133 citation statements)

References 39 publications

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“…Sharp et al (2016) and Alexandre et al (2012). Whereas Alexandre et al (2012) and Sharp et al (2016) Dodd and Sharp (2010) suggests that phytoliths formed in equilibrium with a water of isotope composition close to that of the bulk leaf water. This is additionally supported by the obtained averaged value of λ Phyto−LW (0.522 ± 0.001) close to the θ SiO 2 −water equilibrium value of 0.524 calculated for 25 • C from Sharp et al (2016).…”

Section: Imprint Of Changes In Atmospheric Rh On the 17 O-excess Of Pmentioning

confidence: 98%

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The triple oxygen isotope composition of phytoliths as a proxy of continental atmospheric humidity: insights from climate chamber and climate transect calibrations

et al. 2018

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Abstract. Continental atmospheric relative humidity (RH) is a key climate parameter. Combined with atmospheric temperature, it allows us to estimate the concentration of atmospheric water vapor, which is one of the main components of the global water cycle and the most important gas contributing to the natural greenhouse effect. However, there is a lack of proxies suitable for reconstructing, in a quantitative way, past changes of continental atmospheric humidity. This reduces the possibility of making model-data comparisons necessary for the implementation of climate models. Over the past 10 years, analytical developments have enabled a few laboratories to reach sufficient precision for measuring the triple oxygen isotopes, expressed by the 17 O-excess ( 17 O-excess = ln (δ 17 O + 1) -0.528 × ln (δ 18 O + 1)), in water, water vapor and minerals. The 17 O-excess represents an alternative to deuterium-excess for investigating relative humidity conditions that prevail during water evaporation. Phytoliths are micrometric amorphous silica particles that form continuously in living plants. Phytolith morphological assemblages from soils and sediments are commonly used as past vegetation and hydrous stress indicators. In the present study, we examine whether changes in atmospheric RH imprint the 17 O-excess of phytoliths in a measurable way and whether this imprint offers a potential for reconstructing past RH. For that purpose, we first monitored the 17 O-excess evolution of soil water, grass leaf water and grass phytoliths in response to changes in RH (from 40 to 100 %) in a growth chamber experiment where transpiration reached a steady state. Decreasing RH from 80 to 40 % decreases the 17 Oexcess of phytoliths by 4.1 per meg/% as a result of kinetic fractionation of the leaf water subject to evaporation. In order to model with accuracy the triple oxygen isotope fractionation in play in plant water and in phytoliths we recommend direct and continuous measurements of the triple isotope composition of water vapor. Then, we measured the 17 O-excess of 57 phytolith assemblages collected from top soils along a RH and vegetation transect in inter-tropical West and Central Africa. Although scattered, the 17 O-excess of phytoliths decreases with RH by 3.4 per meg/%. The similarity of the trends observed in the growth chamber and nature supports that RH is an important control of 17 O-excess of phytoliths in the natural environment. However, other parameters such as changes in the triple isotope composition of the soil water or phytolith origin in the plant may come into play. Assessment of these parameters through additional growth chambers experiments and field campaigns will bring us closer to an accurate proxy of changes in relative humidity.

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Section: Imprint Of Changes In Atmospheric Rh On the 17 O-excess Of Pmentioning

confidence: 98%

“…(Table 2) using the Dodd and Sharp (2010) fractionation factor and compared it to the precipitation-weighted δ 18 O Pre−rd0 > 1 average. For the humid forest assemblages, δ 18 O PhytoFW values are higher than δ 18 O Pre−rd0 > 1 by 4.6 ± 1.5 ‰.…”

Section: Imprint Of Changes In Atmospheric Rh On the 17 O-excess Of Pmentioning

confidence: 99%

The triple oxygen isotope composition of phytoliths as a proxy of continental atmospheric humidity: insights from climate chamber and climate transect calibrations

et al. 2018

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“…The δ 18 O diatom composition is strongly dependent on T lake during diatom growth (Brandriss et al, 1998;Schmidt et al, 2001;Dodd and Sharp, 2010). The temperature relationship of the silica-water fractionation is described with a relatively constant δ 18 O-temperature coefficient of − 0.2‰/°C (Dodd et al, 2012).…”

Section: Lake Water Temperaturementioning

confidence: 99%

“…Several experimental studies describe the temperature-dependency of the silica-water fractionation, expressed in different fractionation factors (α (silica-water); e.g. Juillet-Leclerc and Labeyrie, 1987;Dodd and Sharp, 2010). A compilation of different fractionation factors (Dodd et al, 2012), leads to an average α (silica-water) value of 1.038 ± 0.004, taking under consideration isotopic fractionation at a modern Two-Yurts Lake water temperature of~10°C (as measured in the field).…”

Section: Lake Water Temperaturementioning

confidence: 99%

Oxygen isotope composition of diatoms as Late Holocene climate proxy at Two-Yurts Lake, Central Kamchatka, Russia

Meyer

Chapligin

Hoff

et al. 2015

Global and Planetary Change

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Especially in combination with other proxies, the oxygen isotope composition of diatom silica (δ 18 O diatom ) from lake sediments is useful for interpreting past climate conditions. This paper presents the first oxygen isotope data of fossil diatoms from Kamchatka, Russia, derived from sediment cores from Two-Yurts Lake (TYL). For reconstructing Late Holocene climate change, palaeolimnological investigations also included diatom, pollen and chironomid analysis. The most recent diatom sample (δ 18 O diatom = +23.3‰) corresponds well with the present day isotopic composition of the TYL water (mean δ 18 O = −14.8‰) displaying a reasonable isotope fractionation in the system silicawater. Nonetheless, the TYL δ 18 O diatom record is mainly controlled by changes in the isotopic composition of the lake water. TYL is considered as a dynamic system triggered by differential environmental changes closely linked with lake-internal hydrological factors. The diatom silica isotope record displays large variations in δ 18O diatom from +27.3‰ to +23.3‰ from about 4.5 kyr BP until today. A continuous depletion in δ 18O diatom of 4.0‰ is observed in the past 4.5 kyr, which is in good accordance with other hemispheric environmental changes (i.e. a summer insolation-driven Mid-to Late Holocene cooling). The overall cooling trend is superimposed by regional hydrological and atmospheric-oceanic changes. These are related to the interplay between Siberian High and Aleutian Low as well as to the ice dynamics in the Sea of Okhotsk. Additionally, combined δ 18O diatom and chironomid interpretations provide new information on changes related to meltwater input to lakes. Hence, this diatom isotope study provides further insight into hydrology and climate dynamics of this remote, rarely investigated area.

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“…Dodd and Sharp (2010) showed that maturation is a process that occurs in 119 the water column or at the latest at the sediment-water interface. They comment that in the 120 case of deep lacustrine environments, where the bottom water remains at a nearly constant 121 .…”

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confidence: 99%

Recent advances in isotopes as palaeolimnological proxies

Leng

Henderson

2013

J Paleolimnol

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12Isotope geochemistry is an essential part of environmental and climate change research and 13 over the last few decades has contributed significantly to our understanding of a huge array of 14 environmental problems, not least in palaeolimnology and limnogeology. Here we describe 15 some of the recent developments in the use of stable isotopes in palaeo-lake research. These 16 are: better preparation, analysis, and interpretation of biogenic silica oxygen and silicon 17 isotopes; extraction and characterisation of specific compounds such as leaf waxes and algal 18 lipids for isotope analysis; determining the excess of

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A laser fluorination method for oxygen isotope analysis of biogenic silica and a new oxygen isotope calibration of modern diatoms in freshwater environments

Cited by 85 publications

References 39 publications

The triple oxygen isotope composition of phytoliths as a proxy of continental atmospheric humidity: insights from climate chamber and climate transect calibrations

The triple oxygen isotope composition of phytoliths as a proxy of continental atmospheric humidity: insights from climate chamber and climate transect calibrations

Oxygen isotope composition of diatoms as Late Holocene climate proxy at Two-Yurts Lake, Central Kamchatka, Russia

Recent advances in isotopes as palaeolimnological proxies

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