What drives the silicon budget in the Bay of Bengal? The isotope composition clues…

Science Highlights

12 February 2015

The first data set of dissolved silicon isotope composition (δ30Si) along with concentrations (DSi) in seawater of the northern Indian Ocean is presented from the Bay of Bengal (BoB) region.

Elevated Si (>3 µmol/kg) in surface waters of coastal stations indicates the continental supply, whereas a spike of Si (~30 µmol/kg) and a salinity maxima at depth 60 m of the southernmost station hint at intrusion of the Arabian Sea High Salinity waters. In the central bay, higher δ30Si in surface waters indicates greater utilisation of the available Si via diatom production. DSi and δ30Si in surface waters of the BoB vary dramatically in response to the Si supply and its consumption through biological production.

Modelling δ30Si in the deep/bottom waters of the BoB hints at dissolution of diatoms rather than lithogenic clays at/near the sediment­–water interface as the main cause of the elevated Si concentrations in the bay.

15 SantinderSingh l
Figure. Depth profiles of dissolved Si concentrations (left panel) and δ30Si (right panel) are shown for the coastal stations 0814–0820 (upper panel) and open ocean stations 0806–0813 (lower panel). Locations of coastal and open ocean stations are also given. Click here to view the figure larger.

 

Reference:

Singh, S.P., Singh, S.K., Bhushan, R., Rai, V.K., 2015. Dissolved silicon and its isotopes in the water column of the Bay of Bengal: Internal cycling versus lateral transport. Geochimica et Cosmochimica Acta 151, 172-191. doi:10.1016/j.gca.2014.12.019. Click here to access the paper.

Latest highlights

Mercury content and isotopes in bird’s guano: a window to reconstruct past climates

By analysing peat cores, Chuxian Li and her colleagues have shown how populations of nesting seabirds have fluctuated on a sub-Antarctic Island over the last 8,000 years.

Contraction of North Atlantic Deep Water during glacial times: a paradigm called into question

Blaser and co-authors propose a new distribution of deep-water masses in the Atlantic Ocean during the Last Glacial Maximum and the Heinrich Stadial..

Authigenic radiogenic neodymium isotope composition traces millennial-scale overturning circulation variability in the Arabian Sea

The neodymium isotopic signature of the sediment authigenic fraction is, a priori, a valuable proxy for reconstructing deep-water mass trajectories…

Magmatic activity at the Carlsberg Ridge in the Indian Ocean triggered by glacial sea-level variation

De and colleagues provide a high-resolution record of magmatic input and associated hydrothermal activity over the past 49 kyr from a core recovered from a magmatic segment of the slow-spreading Carlsberg Ridge in the Indian Ocean.

Rechercher