Dissolved silicon and its isotopes in the water column of the Bay of Bengal: Internal cycling versus lateral transport

The Missing Silica Sink: Revisiting the Marine Sedimentary Si Cycle Using Cosmogenic 32Si

“…Biogenic opal contents of surface slope sediments in the Bay of Bengal measured 1, 3.7, and 5.1 wt % (Morgenstern et al, b; Unger et al, ) for an average of 3.3%. The majority of this deposited biosiliceous material is of marine origin (Unger et al, ), and there is evidence of rapid authigenic clay formation (Rao et al, ; Singh et al, ). Based on 32 Si activities from our sites (subtropical, temperate ratios), we conservatively predict that an additional ~3.3% SiO 2 is buried as bSi clay .…”

A Review of the Stable Isotope Bio-geochemistry of the Global Silicon Cycle and Its Associated Trace Elements

“…This DSi depletion is associated with an isotope fractionation, imparting SAMW and AAIW a high δ 30 Si DSi signature (de Souza et al, 2012a), a process that has been dubbed "Southern Ocean isotope distillation" by Brzezinski and Jones (Brzezinski and Jones, 2015). The high δ 30 Si DSi signature of SAMW and AAIW is exported to the upper ocean at a near-global scale (De La Rocha et al, 1998;de Souza et al, 2012a,b;Brzezinski and Jones, 2015;Singh et al, 2015). The upper-ocean δ 30 Si DSi distribution thus reflects the importance of Southern Ocean water-mass subduction in resupplying DSi, together with other major nutrients, to the nutrient-poor low-latitude upper ocean.…”

“…Apart from the Atlantic and Arctic Oceans, the deep water δ 30 Si DSi distribution shows markedly little variability, with Indian and Pacific Ocean deep waters exhibiting δ 30 Si DSi values of around +1.2‰ to +1.3‰ (Beucher et al, 2008de Souza et al, 2012a;Grasse et al, 2013;Singh et al, 2015), i.e., essentially invariant considering the degree of analytical consistency between laboratories Grasse et al, 2017). Although there are some hints of heterogeneity in the North Pacific, e.g., in the Cascadia Basin proximal to the North American continent (Beucher et al, 2008), when compared to the ∼0.5‰ meridional gradient observed in the Atlantic Ocean, δ 30 Si DSi variability in the Indian and Pacific Oceans is neither particularly significant nor systematic.…”

GEOTRACES inter-calibration of the stable silicon isotope composition of dissolved silicic acid in seawater

“…Cardinal et al, 2005;Reynolds et al, 2006;Cao et al, 2012;de Souza et al, 2012a;Brzezinski & Jones, 2015;Singh et al, 2015, Zhang et al 2015a. This data set is anticipated to grow as part of the international GEOTRACES program that seeks to understand the global-scale distributions of trace elements and their isotopes in the marine environment (http://www.geotraces.org).…”