River fluxes to the sea from the oceanʼs 10Be/9Be ratio

Blanckenburg, Friedhelm von; Bouchez, Julien

doi:10.1016/j.epsl.2013.11.004

Cited by 69 publications

(89 citation statements)

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“…The evaluation of estuarine exchange processes may also be important to better understand the delivery of trace elements to the ocean (e.g. von Blanckenburg and Bouchez, 2014) or for possible isotopic fractionation of light elements during exchange. Table 3 shows that only less than 1 % of the dissolved riverine Na + load but ca.…”

Section: Magnitude Of Cation Exchange Fluxesmentioning

confidence: 99%

Impact of sediment–seawater cation exchange on Himalayan chemical weathering fluxes

2016

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Abstract. Continental-scale chemical weathering budgets are commonly assessed based on the flux of dissolved elements carried by large rivers to the oceans. However, the interaction between sediments and seawater in estuaries can lead to additional cation exchange fluxes that have been very poorly constrained so far. We constrained the magnitude of cation exchange fluxes from the Ganga-Brahmaputra river system based on cation exchange capacity (CEC) measurements of riverine sediments. CEC values of sediments are variable throughout the river water column as a result of hydrological sorting of minerals with depth that control grain sizes and surface area. The average CEC of the integrated sediment load of the Ganga-Brahmaputra is estimated ca. 6.5 meq 100 g −1 .The cationic charge of sediments in the river is dominated by bivalent ions Ca 2+ (76 %) and Mg 2+ (16 %) followed by monovalent K + (6 %) and Na + (2 %), and the relative proportion of these ions is constant among all samples and both rivers. Assuming a total exchange of exchangeable Ca 2+ for marine Na + yields a maximal additional Ca 2+ flux of 28 × 10 9 mol yr −1 of calcium to the ocean, which represents an increase of ca. 6 % of the actual river dissolved Ca 2+ flux. In the more likely event that only a fraction of the adsorbed riverine Ca 2+ is exchanged, not only for marine Na + but also Mg 2+ and K + , estuarine cation exchange for the GangaBrahmaputra is responsible for an additional Ca 2+ flux of 23 × 10 9 mol yr −1 , while ca. 27 × 10 9 mol yr −1 of Na + , 8 × 10 9 mol yr −1 of Mg 2+ and 4 × 10 9 mol yr −1 of K + are re-absorbed in the estuaries. This represents an additional riverine Ca 2+ flux to the ocean of 5 % compared to the measured dissolved flux. About 15 % of the dissolved Na + flux, 8 % of the dissolved K + flux and 4 % of the Mg 2+ are reabsorbed by the sediments in the estuaries. The impact of estuarine sediment-seawater cation exchange appears to be limited when evaluated in the context of the long-term carbon cycle and its main effect is the sequestration of a significant fraction of the riverine Na flux to the oceans. The limited exchange fluxes of the Ganga-Brahmaputra relate to the lower than average CEC of its sediment load that do not counterbalance the high sediment flux to the oceans. This can be attributed to the nature of Himalayan river sediment such as low proportion of clays and organic matter.

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Section: Magnitude Of Cation Exchange Fluxesmentioning

confidence: 99%

Impact of sediment–seawater cation exchange on Himalayan chemical weathering fluxes

2016

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“…Unlike most isotope systems, the 10 Be/ 9 Be ratio is set by the individual fluxes of the two isotopes into the oceans 10 (see Supplementary Information Sections 1 and 2). Although the flux of meteoric 10 Be to the ocean can be calculated from cosmic ray 10 Be/ 9 Be represent one standard deviation of samples averaged over deep water; error bars of Fe-Mn crust 10 Be/ 9 Be represent the uncertainty of the individual measurements. Most individual ocean 10 Be/ 9 Be ratios are statistically indistinguishable between these di erent timescales, as shown by a t-test yielding p-values >0.05 except for the South Atlantic (p = 0.02).…”

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confidence: 99%

“…3). Ocean basin mass balances show that 10 Be/ 9 Be ratios reflect the terrigenous input into the basins 10 South Atlantic (e). Open red symbols show published 10 Be/ 9 Be ratios, corrected for 10 Be radioactive decay.…”

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Stable runoff and weathering fluxes into the oceans over Quaternary climate cycles

et al. 2015

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Throughout the Quaternary period, the Earth's surface has been subject to large changes in temperature and precipitation associated with fluctuations between glacial and interglacial states that have a ected biogeochemical cycling 1-4 . However, the e ect of these climate oscillations on weathering is debated, with climate modelling e orts using empirical relationships between measures of climate and weathering 1,5,6 suggesting minimal changes in global weathering rates between these two climate states 7,8 . The ratio of the cosmogenic isotope 10 Be, which is produced in the atmosphere and deposited to the oceans and the land surface, to 9 Be, which is introduced to the oceans by the riverine silicate weathering flux, can be used to track relative weathering fluxes 9,10 . Here we apply this proxy to marine sediment beryllium records 11-16 spanning the past two million years, and find no detectable shifts in inputs from global silicate weathering into the oceans. Using climate model simulations of the Last Glacial Maximum 17 along with a model for silicate weathering 18 , we find that there was large regional variability in runo between glacial and interglacial periods, but that this regional variability was insu cient to shift global weathering fluxes. We suggest that this stability in weathering explains the observation 19 that the removal of CO 2 from the atmosphere by silicate weathering has been in approximate balance with CO 2 degassing over the past 600,000 years.During Quaternary interglacial periods the Earth's surface is subjected to warmer temperatures, a shifted and more intense hydrologic cycle 20 , ecosystem change, and higher atmospheric CO 2 concentrations 19 than during glacial periods. Weathering is sensitive to climate 6 , and an increase in weathering flux is thought to follow exposure of glacial debris at glacial terminations 21 . Yet, empirical watershed relationships between measures of climate and weathering 1,5 , combined with global-scale climate simulations that pair runoff distributions with lithology, have suggested small changes in global weathering fluxes 7,8 . A test of these predictions is still pending, as direct evidence regarding global weathering and sediment 2 fluxes over glacial and interglacial timescales is scarce. Only increased weathering in large floodplains over the Holocene has been reported 3 . Further, radiogenic isotopes measured in the ocean sedimentary record show glacial-interglacial shifts 1 , but these proxies may reflect changes in the source and the style of weathering 21,22 , rather than changes in flux.To directly measure relative weathering fluxes over glacial-interglacial variations, we used the 10 Be(meteoric)/ 9 Be ratio 9 . Unlike most isotope systems, the 10 Be/ 9 Be ratio is set by the individual fluxes of the two isotopes into the oceans 10 (see Supplementary Information Sections 1 and 2). Although the flux of meteoric 10 Be to the ocean can be calculated from cosmic ray 0.0 0.5 1.0 1.5 2.0 Pacific South Atlantic− Indian North Atlantic Mediterranean...

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“…The cosmogenic Be isotope 10 Be in seawater has been investigated by using accelerator mass spectrometry (e.g., Raisbeck et al) [4]. The ratio of cosmogenic 10 Be to lithogenic stable Be is expected to be a new chemical tracer for the contribution of terrigenous matter to the sea [5,6] and water masses in the ocean [7]. The 10 Be/Be ratio in deep waters increases with the age of the water mass, which is mainly a consequence of the 2.5-fold increase in the 10 Be concentration along the deep thermohaline circulation from the deep north Atlantic to the deep north Pacific [8,9].…”

Section: Introductionmentioning

confidence: 99%

Determination of picomolar beryllium levels in seawater with inductively coupled plasma mass spectrometry following silica-gel preconcentration

Tazoe

Yamagata

Obata³

et al. 2014

Analytica Chimica Acta

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River fluxes to the sea from the oceanʼs 10Be/9Be ratio

Abstract: . (2014): River fluxes to the sea from the ocean's 10Be/9Be ratio. AbstractThe ratio of the meteoric cosmogenic radionuclide 10

Cited by 69 publications

References 44 publications

Impact of sediment–seawater cation exchange on Himalayan chemical weathering fluxes

Impact of sediment–seawater cation exchange on Himalayan chemical weathering fluxes

Stable runoff and weathering fluxes into the oceans over Quaternary climate cycles

Determination of picomolar beryllium levels in seawater with inductively coupled plasma mass spectrometry following silica-gel preconcentration

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