High particulate organic carbon export in the Arabian Sea

In the framework of Indian GEOTRACES cruise GI02, high-resolution sampling was carried out in the Arabian Sea and the Indian Ocean during April–May 2014. The first 234Th-based carbon export flux ever made in the southern Arabian Sea are presented. In contrast to episodic decrease of primary production from 17°N to 16°S, POC export fluxes show high values  (up to 9 mmol m-2 d-1), definitely larger than what was observed in the Bengal Bay at the same season. 234Th deficit in subsurface depths is due to the diel vertical migration, grazing, and fecal pellet production by mesozooplankton. Interestingly, the modelled POC export fluxes from in situ and satellite-derived primary production are higher than the field values (234Th-Based) for two models and are comparable for a third one, discrepancies discussed in the paper.

18 Subha 2Figures: (A) Depth-latitude vertical profile of oxygen saturation (%) (white contour lines) is shown relative to 234Th/238U activity ratio (A.R.) along the 65°E meridional section of the Arabian Sea and the Indian Ocean. (B) Plot showing relation between primary production and POC export flux. The POC export flux sinking out of the euphotic zone was derived by Laws, Dunne and Henson’s models. Dashed trend lines represent export efficiencies of 2, 5, 10 and 20%. Click here to view the figure larger.


Subha Anand, S., Rengarajan, R., & Sarma, V. V. S. S. (2018). Th-234 Based Carbon Export Flux along the Indian GEOTRACES GI02 Section in the Arabian Sea and the Indian Ocean. Global Biogeochemical Cycles, 32(3), 417–436. http://doi.org/10.1002/2017GB005847

Latest highlights

Science Highlights

Loss of old Arctic sea ice increases methylmercury concentrations

Researchers from the SCRIPPS, the Stockholm Natural Museum and the Mediterranean Institute of Oceanography show the importance of sea ice composition on methylmercury budgets


Science Highlights

Estimating Atmospheric Trace Element Deposition Over the Global Ocean

A recently developed method based on the natural radionuclide Be-7 has provided a means to estimate the bulk atmospheric trace element deposition velocity

Science Highlights

Dissolved gallium unravels Pacific and Atlantic waters in the Arctic Ocean

Whitmore and co-workers demonstrate that the dissolved gallium distribution provide a better water source deconvolution than the nutrient tracers


Science Highlights

Precise estimate of the mercury export from the Arctic to the Atlantic Ocean

Using new observations acquired during GEOTRACES Arctic cruises, a refined arctic mercury budget has been established