What did we do? Oceanic water mass is a mixture of waters with varying ages, and the transit time distribution (TTD) measures its age spectrum. We construct a model-based TTD using the data-constrained circulation fields from the ECCO-JPL ocean data assimilation, and test it against the observed and directly simulated distribution of pCFC-11 from the Pacific and Atlantic basins.
What did we find? Observed distributions of pCFC-11 in the upper ocean thermocline are well reproduced by the convolution integral of the model-based TTD (mean bias<6%, spatial correlation>0.87) but there are significant regional biases in particular near the base of the thermocline and in the deep water formation regions.
Why is it important? Age of water is an important concept for the tracer studies. The ECCO-JPL circulation provides overall reliable estimates of the water age and the upper ocean ventilation rates suitable for biogeochemical studies. We will use this product for the future studies.
Reference: Ito T. and O. Wang, (2017), Transit Time Distribution based on the ECCO-JPL Ocean Data Assimilation, Journal of Marine Systems, doi.org/10.1016/j.jmarsys.2016.10.015