Temporal evolution of tritium-�He age in the North Atlantic : implications for thermocline ventilation

Robbins, Paul E.

doi:10.1575/1912/5712

Cited by 4 publications

(3 citation statements)

References 89 publications

(178 reference statements)

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“…The latter is particularly a problem in the bias of data taken in nonwinter months. Robbins [1997] has a thorough evaluation of errors related to interpolation and finds errors will increase with increasing tritium/3He age. Sarmiento [1990], it is possible that in other regions corrections would be larger.…”

Section: Discussion Of Cfc Agesmentioning

confidence: 99%

Circulation and ventilation flux of the Pacific Ocean

Fine¹,

Maillet²,

Sullivan³

et al. 2001

J. Geophys. Res.

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Section: Discussion Of Cfc Agesmentioning

confidence: 99%

Circulation and ventilation flux of the Pacific Ocean

Fine¹,

Maillet²,

Sullivan³

et al. 2001

J. Geophys. Res.

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“…Present analytical uncertainty for CFC-11, CFC-12, and SF 6 is usually less than 3%. When using tracer data, there will be errors related to spatial (Robbins 1997) and temporal resolution. Recent work shows that in regions of high eddy activity, a discrete tracer measurement may be biased by eddy variability (Peacock et al 2005, Waugh & Abraham 2008see below).…”

Section: Shipboard Measurementsmentioning

confidence: 99%

Observations of CFCs and SF₆ as Ocean Tracers

Fine

2011

Annu. Rev. Mar. Sci.

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An advantage of using chlorofluorocarbons (CFCs) and sulfur hexafluoride (SF6) as tracers of ocean circulation is that the time-dependent source functions permit calculation of rates for ocean processes. These compounds are also sensitive indicators highlighting interior ocean regions where surface-derived anomalies can be transported on timescales of decades. Significant applications for CFCs have been for the deep limb of the Atlantic meridional overturning circulation, upper ocean ventilation, and biogeochemical rates, including apparent oxygen utilization rates and anthropogenic CO2 inventories. Although CFCs have started to decrease in the atmosphere, SF6 continues to increase. There are benefits to measuring both CFCs and SF6: A large global CFC data set exists; CFCs are still increasing in older waters; SF6 expands estimates of age; and calculations of anthropogenic CO2 inventory are enhanced. Thus, the outlook for using CFCs as tracers for oceanic processes, and in particular in concert with SF6, remains very positive.

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“…First‐order scaling arguments suggest that isopycnal advection and diffusion occur on faster timescales than diapycnal diffusion in the thermocline. This scaling, however, does not account for complex, three‐dimensional circulation patterns (e.g., the vertical shear in the advective flow) which could enhance the effects of diapycnal diffusion [ Robbins , 1997]. However, in model runs including diapycnal diffusion, diffusivities on the order of 10 −5 m 2 s −1 (Figure 6b) do not, indeed, significantly alter the tracer distributions on σ θ = 26.0 kg m −3 based on advection only (Figure 6a).…”

Section: Role Of Diffusion and Outcrop Boundary Conditionsmentioning

confidence: 99%

Influence of mixing on CFC uptake and CFC ages in the North Pacific thermocline

Mecking

2004

J. Geophys. Res.

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[1] A diagnostic, isopycnal advection-diffusion model based on a climatological, geostrophic flow field is used to study the uptake of chlorofluorocarbons (CFCs) into the portion of the thermocline that outcrops in the open North Pacific (s q 26.6 kg m À3 ). In addition to advection, isopycnal diffusion is required to match the CFC data collected during the World Ocean Circulation Experiment (WOCE) in the early 1990s. Using reduced outcrop saturations of 80-95% for isopycnals outcropping in the northwestern North Pacific (s q ! 25.4 kg m À3 ), together with an isopcynal interior diffusivity of 2000 m 2 s À1 and enhanced diffusion (5000 m 2 s À1 ) in the Kuroshio Extension region, further improves the model-data agreement. Along-isopycnal diffusion is particularly important for isopycnals with shadow zones/pool regions in the western subtropical North Pacific that are isolated from direct advective ventilation. The isopycnal mixing causes an estimated increase in CFC-12 inventories on these isopycnals, compared to advection only, ranging from 10-20% (s q = 25.6 kg m À3 ) to 50-130% (s q = 26.6 kg m À3) over the subtropics in 1993. This contribution has important consequences for subduction rate estimates derived from CFC inventories and for the location of the subsurface CFC maxima. When tracer ages are derived from the modeled CFC distributions, time-evolving mixing biases become apparent that reflect the nonlinearities in the atmospheric CFC time histories. Comparison with model-calculated ideal ages suggests that during the time of WOCE ($1993), ventilation ages based on CFC-12 were biased young by as much as 16-24 years for pCFC-12 ages of 25 years, underestimating ideal ages by as much as 40-50%.

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Temporal evolution of tritium-�He age in the North Atlantic : implications for thermocline ventilation

Cited by 4 publications

References 89 publications

Circulation and ventilation flux of the Pacific Ocean

Circulation and ventilation flux of the Pacific Ocean

Observations of CFCs and SF₆ as Ocean Tracers

Influence of mixing on CFC uptake and CFC ages in the North Pacific thermocline

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Temporal evolution of tritium-�He age in the North Atlantic : implications for thermocline ventilation

Cited by 4 publications

References 89 publications

Circulation and ventilation flux of the Pacific Ocean

Circulation and ventilation flux of the Pacific Ocean

Observations of CFCs and SF6 as Ocean Tracers

Influence of mixing on CFC uptake and CFC ages in the North Pacific thermocline

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Product

Resources

About

Observations of CFCs and SF₆ as Ocean Tracers