Water masses in the Atlantic Ocean: water mass ages and ventilation
Year: 2026
Type: article
Abstract: . The distribution of oceanic water masses and their properties, such as ventilation constitute fundamental parameters, for instance, the thermohaline circulation patterns and biogeochemical processes in the marine systems. The distributions of main water masses in the Atlantic Ocean have been comprehensively documented in a companion study (Liu and Tanhua, 2021), this study presents quantitative assessments of water mass age characteristics and ventilation time scales through multi-tracer analysis incorporating chlorofluorocarbon-12 (CFC-12), sulfur hexafluoride (SF6), and argon-39 (39Ar). Here we use two distinct age concepts: mean-age as an integrative metric of water mass chronology, and mode-age as a proxy for advective time scales. Empirical results demonstrate systematic age progression with increasing pressure and along water mass trajectories. Surface layer central waters exhibit mean ages up to ~100 years and mode ages reaching ~30 years. In the intermediate layer, meridional age gradients characterize the Antarctic Intermediate Water (AAIW) reaching maximum mean-age (~300 years) and mode-age (~80 years) at 30 °N, whereas zonal variations manifest in Mediterranean Water (MW) with peak values (~400 years in mean-age, ~100 years in mode-age) observed in equatorial regions. As the dominant deep water component, North Atlantic Deep Water (NADW) exhibits extreme ages in the Antarctic Circumpolar Current (ACC) region at 50°S, achieving mean age ~600 years and mode age ~100 years. Bottom layer water masses display their oldest signatures: Antarctic Bottom Water (AABW) from the Weddell Sea reaches ~600 years (mean) and ~100 years (mode) at equatorial latitudes, while its extension, Northeast Atlantic Bottom Water (NEABW), attains exceptional values of ~800 years (mean) and ~120 years (mode) at 50°N. The age analysis reveals significant basin-scale asymmetries, with eastern basins exhibiting younger ages compared to western counterparts. Ventilation efficiency modulates these age distributions, as evidenced by lower mode-ages and reduced apparent oxygen utilization (AOU) in better-ventilated western basins. The calculated oxygen utilization rate (OUR) demonstrates spatial concordance with dissolved oxygen (DO) concentrations, corroborating enhanced oxidative processes in high-oxygen regimes. This integrated age framework provides novel insights into water mass ventilation dynamics and their biogeochemical implications through quantitative characterization of temporal-spatial age distributions across multiple oceanographic provinces. Key words: Water Mass, Atlantic Ocean, Transient Tracer, Mean- and Mode-age, Ventilation, GLODAPv2 data product
Source: Ocean science
Authors: Mian Liu, Toste Tanhua
Language: English
Subfield: Oceanography
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,412
OpenAlex ID: W7204450435