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Published on: August 22, 2014
Quantifying He fluxes from the mantle using multi-tracer data assimilation.
1Alfred Wegener Institute, Helmholtz-Center for Polar- and Marine Research, Am Alten Hafen 26, 27568 Bremerhaven, Germany reiner.schlitzer@awi.de.
Summary
This study refines estimates of mantle helium-3 (³He) release from mid-ocean ridges using an ocean model. It suggests previous estimates were too high, proposing a new global flux and identifying localized sources in the Lau Basin.
Area of Science:
- Oceanography
- Geochemistry
- Isotope Geochemistry
Background:
- Mantle helium (³He and ⁴He) is released from mid-ocean ridges, influencing ocean chemistry.
- Previous estimates of global mantle ³He flux may be inaccurate.
- Understanding helium distribution is crucial for oceanographic and geochemical studies.
Purpose of the Study:
- To simulate ³He and ⁴He distributions in the ocean using a global model.
- To reassess global mantle ³He flux based on model-data agreement.
- To identify potential localized sources of helium release.
Main Methods:
- Utilized a coarse-resolution global ocean model calibrated with geostrophic shear and hydrographic data.
- Compared model-simulated ³He and ⁴He distributions with observational data (¹⁴C, CFCs).
- Performed misfit analysis to identify discrepancies between model and data, particularly for δ³He.
Main Results:
- The model accurately reproduces ¹⁴C and chlorofluorocarbon data, indicating realistic ocean circulation.
- Optimal global mantle ³He flux is estimated at 450 ± 50 mol ³He yr⁻¹, approximately half of previous estimates.
- A significant underestimation of δ³He in the southwestern Pacific, specifically the Lau Backarc Basin, was identified and resolved by introducing a localized flux.
Conclusions:
- Previous global mantle ³He fluxes are likely overestimated by a factor of two.
- A global flux of 450 ± 50 mol ³He yr⁻¹ provides optimal agreement with observational data.
- Localized helium release from the Lau Basin, not currently accounted for, is necessary to explain observed δ³He anomalies.
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