Helium-3 plumes in the deep Indian Ocean confirm hydrothermal activity

Thanks to samples collected as part of the Japanese GEOTRACES cruise in 2009 – 2010, along section GI04, Takahata and co-workers (2018, see reference below) identified a maximum helium-3 ratios value (δ3He >14%) at mid-depth (2000 – 3000 m) in the northern part (north of 30°S) of the central Indian Ocean, whereas lower ratio was found in the southern part at the same depth. These values identify an hydrothermal helium-3 plume originating from the Central Indian Ridge around 20°S flowing eastward from the ridge as previously reported in WOCE cruises. Another hydrothermal source of helium-3 is observed in the Gulf of Aden, also helping to constrain the deep circulation off the North East African coast.

18 Takahata
Figure: Vertical distribution of excess helium-3 (3He) along 70˚E of the central Indian Ocean. Two hydrothermal plumes are identified at mid-depth; one is from the Central Indian Ridge and the other from Gulf of Aden. Click here to view it larger.

Reference:

Takahata, N., Shirai, K., Ohmori, K., Obata, H., Gamo, T., & Sano, Y. (2018). Distribution of helium-3 plumes and deep-sea circulation in the central Indian Ocean. Terrestrial, Atmospheric and Oceanic Sciences, 29(3), 331–340. http://doi.org/10.3319/TAO.2017.10.21.02

Latest highlights

Iron and zinc isotopes disentangle the anthropogenic, natural and wildfire sources of aerosols over the North and Equatorial Pacific Ocean

Bunnell and co-authors analysed aerosol iron and zinc isotopic compositions along the North Pacific GEOTRACES GP15 section (Alaska-Tahiti).

Contribution of sandy beaches to the oceanic silica cycle

This paper calls into question the commonly accepted idea of an oceanic silicon cycle in equilibrium.

North – South contrasting behavior of dissolved cobalt in the Indian Ocean

Malla and Singh have studied the complex biogeochemical processes of total dissolved cobalt in the Indian Ocean.

The Amazonian mangrove systems accumulate and release dissolved neodymium and hafnium to the oceans

Xu and colleagues investigated the concentrations of rare earth elements in the Amazonian mangrove.

Rechercher