Loihi Seamount, hydrothermal Helium-3 and dissolved iron sources and their dispersion within the Pacific Ocean

As part of the GEOTRACES cruise GP15, Jenkins and co-workers (2020, see reference below) observed large water column anomalies in helium isotopes and trace metal concentrations above the Loihi Seamount (~19°N, 154°W) that extends along the GP15 track for hundreds of kilometers. Expanding their data with historical ones, they observe that the Loihi Helium-3 (3He) and dissolved iron (dFe) “signal” was propagating at depth of 1100 m within ∼100 – 1000 km of Loihi, characterized by a distal dFe:3He ratio of ∼4 ×106. Contrastingly, no major methane input was observed. Modeling the regional circulation allowed these authors to estimate a hydrothermal 3He source from Loihi of 10.4 ±4.2 mol a−1 and a corresponding dFe flux of ∼40 Mmol a−1. On a larger scale, they simulate that the Loihi-influenced waters (enriched in He and Fe) eventually upwell along the west coast of North America, also extending around 1000 km into the northwest Pacific Ocean, which could play a role in fertilizing the subpolar North Pacific Ocean.

Figure: (a) A map showing the distribution of 3He anomalies at a depth of 1100 m in the subtropical North Pacific (note the eastward plume emanating from Hawaii) and the GEOTRACES GP15 station locations (red stars), (b) the location of the stations closest to the Loihi source, (c) the size of the 1100 m 3He anomaly observed during GP15 (red stars) and previous stations (black dots), and (d) modelled upwelling intensities for the Loihi source.


Jenkins, W. J., Hatta, M., Fitzsimmons, J. N., Schlitzer, R., Lanning, N. T., Shiller, A., Buckley, N. R., German, C. R., Lott, D. E., Weiss, G., Whitmore, L., Casciotti, K., Lam, P. J., Cutter, G. A., Cahill, K. L. (2020). An intermediate-depth source of hydrothermal 3He and dissolved iron in the North Pacific. Earth and Planetary Science Letters, 539, 116223. DOI: https://doi.org/10.1016/j.epsl.2020.116223

Latest highlights

Science Highlights

Rare Earth Elements and neodymium isotopes as tracers in the Mediterranean Sea

Garcia-Solsona and co-workers analysed 9 seawater stations around the central Mediterranean Sea…


Science Highlights

A new model simulates the speciation and dispersion of hydrothermal iron

Roshan and collaborators present new observations of dissolved iron and its physical speciation in the South Pacific


Science Highlights

Mechanisms driving biological CO2 drawdown in the Subarctic Pacific unraveled

Nishioka and co-authors compiled comprehensive data sets of iron and macronutrients covering the whole subarctic Pacific…


Science Highlights

The biogeochemical ventures of dissolved iron and manganese across the Arctic Ocean

The spatial distributions and biogeochemical cycling of dissolved Fe (dFe) and dissolved manganese (dMn) across the Arctic Ocean were established during summer and fall 2015. The Canadian GEOTRACES transect extended from the Canada Basin (CB) to the Labrador Sea (LS) via the Canadian Arctic Archipelago (CAA). The surface, subsurface and deep water distributions for both […]