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The Ocean's Global 39 Ar Distribution Estimated With an Ocean Circulation Inverse Model
Author(s) -
Holzer Mark,
DeVries Timothy,
Smethie William
Publication year - 2019
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2019gl082663
Subject(s) - latitude , environmental science , atmosphere (unit) , ocean current , climatology , atmospheric sciences , geology , meteorology , geography , geodesy
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.