Calcium isotope ratios in the world's largest rivers: A constraint on the maximum imbalance of oceanic calcium fluxes

Abstract

[1] The oceanic mass balance of calcium (Ca) is defined by a balance between the inputs (rivers and hydrothermal) and outputs (bulk carbonate) of Ca. Large rivers were analyzed for Ca isotope ratios ( 44 Ca/ 42 Ca, expressed as d 44 42 Ca) to investigate the source and cycling of riverine Ca, and to add an isotopic mass balance constraint to the oceanic budget of Ca. The new data account for approximately one-third of the total Ca supplied to the oceans by rivers. Inter-sample and seasonal variability was assessed by analyzing more than one sample for many rivers. The range in the d Ca value of bulk carbonate and the riverine input at the current level of uncertainty. The input and output fluxes could be imbalanced over much shorter time-scales (such as glacial-interglacial cycles), in which case the ocean-carbonate system will not yet have responded, because of the long residence time of Ca. The maximum current flux imbalance of 15% would be sufficient to account for the total variations in Ca concentration over the Tertiary. Such an interpretation is not unique, but is the simplest interpretation given the similarity between the input and output isotopic compositions, and rules out hypotheses of extreme imbalance in the recent global biogeochemical cycle of Ca.Citation: Tipper, E. T., J. Gaillardet, A. Galy, P. Louvat, M. J. Bickle, and F. Capmas (2010), Calcium isotope ratios in the world's largest rivers: A constraint on the maximum imbalance of oceanic calcium fluxes, Global Biogeochem. Cycles, 24, GB3019,

Evidence for stable Sr isotope fractionation by silicate weathering in a small sedimentary watershed in southwestern Taiwan

“…The isotope fractionation driven by precipitation of secondary minerals is an important mechanism and has been indicated in Li, Mg, Ca, and Si isotopic systems (e. g., Chan et al, 1992;Ziegler et al, 2005;Tipper et al, 2006bTipper et al, , 2008Tipper et al, , 2010Tipper et al, , 2012Vigier et al, 2008). Although the stable Sr isotope fractionation associated with secondary silicate minerals has not yet been reported, the formation of carbonate minerals contain lower d 88 Sr values than the parent solutions in marine carbonate, inorganic carbonate, and laboratory precipitation experiments (Fietzke and Eisenhauer, 2006;Rü ggeberg et al, 2008;Bö hm et al, 2012;Raddatz et al, 2013;Stevenson et al, 2014;Vollstaedt et al, 2014).…”

Chemical fluxes from time series sampling of the Irrawaddy and Salween Rivers, Myanmar

“…This is likely to be due to increased inputs from Tibet and the Himalayas as the rains penetrate north at the height of the monsoon. The Sr-isotopic composition of the Salween in Tibet was measured in September 2003 at 0.71274 (Tipper et al, 2010). However the Sr inputs from rivers draining Himalayan metamorphic rocks are markedly more radiogenic and by analogy with the other rivers draining the Himalayas and Tibet (e.g.…”

Controlling factors of Ca isotope fractionation in scleractinian corals evaluated by temperature, pH and light controlled culture experiments

“…Calcium isotope ratios (δ 44 Ca= (( 44 Ca/ 40 Ca) sample /( 44 Ca/ 40 Ca) standard -1) × 1000) of marine carbonates have been used to interpret biogeochemical cycles of Ca in the ocean over geological time (Zhu and Macdougal, 1998;Farkaš et al, 2007;Griffith et al, 2008;Tipper et al, 2010), mass extinction events (Payne et al, 2010), food-webs (Skulan et al, 1997;Clementz et al, 2003;Heuser et al, 2011), variation of water temperature (Nägler et al, 2000;Gussone et al, 2004;Immenhauser et al, 2005;Hippler et al, 2006) and diagenesis (cf. Teichert et al, 2009).…”