The concept of age in marine modelling

Iodine-129,137Cs, and CFC-11 tracer transit time distributions in the Arctic Ocean

“…[4] Recent studies [Waugh et al, 2003;Waugh and Hall, 2005] have shown that when mixing is included in empirical models, there is no single, unique transit time that describes fluid flow in the ocean. Instead, the flow of water arriving at a specific location is more accurately characterized by a range of transit times termed the transit time distribution (TTD) [Beining and Roether, 1996;Deleersnijder et al, 2001;Haine and Hall, 2002]. Tracers having different input functions will weigh the TTD in different ways and can provide different estimates of tracer ages (defined as the elapsed time since an interior concentration was equivalent to that of the input function) for the same flow structure, but the TTD, itself is an intrinsic property of the flow from a specified source region [Waugh et al, 2003].…”

The age of Yellow River water in the Bohai Sea

“…[2] Advection and diffusion are two important processes controlling material transport in coastal water. Because of the complex spatiotemporal structure of these processes, it is helpful to define auxiliary variables, such as water exchange timescale and water age, to quantify their environmental function in coastal water [Zimmerman, 1976;Takeoka, 1984;Deleersnijder et al, 2001;Monsen et al, 2002;Delhez et al, 2004].…”

“…Observational techniques, including the isotope-tracer decaying method and the lag time method, are widely used to measure mean water age [e.g., Adkins and Boyle, 1997;Peeters et al, 2000;Hansell et al, 2004;Kershaw et al, 2004;Anderson et al, 2010]. However, these methods may underestimate the true mean water age if diffusion is considered [Deleersnijder et al, 2001;Delhez et al, 2003;. Theoretical analysis is helpful for understanding mean water age [e.g., Wunsch, 2002] because instructive analytical solutions may be obtained.…”

“…[6] There are two widely used numerical methods for calculating mean water age. One method is the particle-tracking method (PTM) [Chen, 2007;Liu et al, 2011], and the other method is the constituent-oriented age and residence time theory (CART, see www.climate.be/cart) [Deleersnijder et al, 2001;Gong et al, 2009;de Brye et al, 2012]. These two methods are essentially equivalent, although their simulation results are not identical in practice.…”

Accumulation of conservative substances in a sub-tropical coastal lagoon

“…On the other hand, the "water age" or "age tracer" is calculated by using an aging term in the advection-diffusion equation (England, 1995;Delhez et al, 1999;Deleersnijder et al, 2001). The age tracer is usually set to zero in a boundary and reaches steadystate conditions when a balance between water aging and the flux of younger water is attained.…”