Application of Barium Isotopes in tracing oceanographic processes

• Main Author: PANIGRAHI, NIHARIKA
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: SPAST Foundation 2021
• Subjects: Southern Ocean
• Online Access: https://spast.org/techrep/article/view/2816

This study reviews the current status of Barium (Ba) isotope systematics in modern marineenvironment to explore its scope as proxies of modern and past oceanographic processes(Bates et al., 2017; Cao et al., 2016; Horner et al., 2015; Hsieh & Henderson, 2017). In thisresearch work, attempts were be made to understand the analytical challenges andadvantages/limitations of Ba isotope systematics over the well-established Ba concentrationbasedproxies in learning oceanographic processes. The typical depth profiles (Figure 1) ofdissolved Ba [DBa] and its isotope composition in modern seawater are nearly depth invariantin the upper water column indicating the predominant role of water mixing over its utilizationin surface ocean biological productivity. Ba isotope composition in the suspended of the upperwater column reflect that of dissolved pool but with a constant negative offset. The gradualincrease in [DBa] concentration and decrease in Ba isotope composition are generally foundin deeper waters at each station and also along the global ocean conveyor belt. Thisobservation strongly suggests an accumulation of lighter Ba isotopes in deep waters suppliedfrom upper oceans. The close linear relationship (?2=0.90,?=145) between δ138/134BaNIST and1/[DBa] suggests the mixing between the deep Southern Ocean and North Pacific surfacewater (Figure 2). This fractionation is largely controlled by the addition/removal of [DBa] as thenutrient-rich Circumpolar Deep Water upwells in the North Pacific. The addition ofhydrothermal fluids (~2000m–3000) results in the non-conservative behaviour of Ba in theSouth-East Atlantic. The marginal seas away from the direct riverine inputs also show a Bacycling similar to that in global oceans indicating a ubiquitous control mechanism working inmarine environment. The Ba supply from upwelling deep waters of the Southern Ocean andits utilization during organic matter decomposition in the upper water column of global oceansseem to be the primary mechanism.The sedimentary excess of Ba (Baxs) ...