The Ocean's Global 39Ar Distribution Estimated With an Ocean Circulation Inverse Model. Issue 13 (2nd July 2019)

• Record Type: Journal Article
• Authors: Holzer, Mark; DeVries, Timothy; Smethie, William
• Is Part Of: Geophysical research letters. Volume 46:Issue 13(2019)
• Page Start: 7491
• Page End: 7499
• Publication Date: 2019-07-02
• Subjects: ocean ventilation -- ocean circulation -- tracers -- argon age -- ideal mean age -- reservoir age; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2019GL082663
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: 39 Ar with its 269‐year half‐life has great potential for constraining ocean ventilation and transport. Here we estimate the distribution of 39 Ar using a steady ocean circulation inverse model. Our estimates match available 39 Ar measurements to within an absolute error of ∼9% modern argon without major biases. We find that 39 Ar traces out the world ocean's ventilation pathways and that the 39 Ar age Γ Ar and the ideal mean age have broadly similar large‐scale patterns. At the surface, 39 Ar is close to saturated except at high latitudes. Undersaturation imparts a finite 39 Ar age to surface waters relative to the atmosphere, with peak values exceeding 100 years in Antarctic waters. This reservoir age is propagated into the interior with Antarctic Bottom Water, elevating Γ Ar by ∼50 years in the deep Pacific and Indian oceans. Our estimates identify the large‐scale gradients and uncertainty patterns of 39 Ar, thus providing guidance for future measurements. Key Points: We estimate the global three‐dimensional 39 Ar distribution in the ocean using a data‐assimilated circulation model The 39 Ar age correlates with the ideal mean age, encodes TTD‐shape information, and traces out the world ocean's ventilation pathways High‐latitude surface waters are undersaturated in 39 Ar imparting a reservoir age of order 100 years to Antarctic waters