Fig. 1.

Ar, Kr, and Xe isotope ratios measured in the deep ocean at BATS show consistent heavy isotope undersaturation. Isotope ratios are reported as deviations (in ‰) from the well-mixed atmosphere. Markers show replicate-mean values and error bars indicate ±1σ analytical uncertainties (note: error bars may be smaller than markers). Dashed lines represent solubility equilibrium ratios, constrained by a compilation of published (12, 21) and experimental measurements at various temperatures and salinities. Solid lines represent model-simulated isotope ratios at BATS, using the gas-exchange parameterization of ref. 22 with a doubling of bubble-mediated gas exchange.