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.
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