Calibration radiocarbon ocean

Hughen, K. A., J. T. Overpeck, S. J. Lehman, M. Kashgarian, J. Southon, L. C. Peterson, R. Alley, and D. M. Sigman (1998), Deglaciation changes in ocean circulation from an extended radiocarbon calibration, Nature 391, 65-68. 

The so-called titanium method used by Arrhenius et a/. (1951) assumes a so-called lutite veil depositing at a constant rate throughout the deep oceans. Titanium associated with this lutite fraction then is also assumed to accumulate at a constant rate. Variations in the accumulation rates of biogenic components can then be assessed. The initial titanium method was calibrated by a single radiocarbon date as discussed above. The method has not been used since it was discovered that accumulation rates of all detrital and biogenic components of deep-sea sediments are subject to change as a function of climatic history and focusing processes. 

Deglacial changes in ocean circulation from an extended radiocarbon calibration. Nature 391, 65-68. 

Radiocarbon has been used to study thermocline ventilation using tools ranging from simple 3-box models to full 3D ocean circulation models. Many of the ID and 2D models are based on work by W. Jenkins using tritium in the North Atlantic. In a recent example, R. Sonnerup and co-workers at the University of Washington used chlorofluorocarbon data to calibrate a ID (meridional) along-isopycnal advection-diffusion model in the North Pacific with WOCE data. [4] is the basic equation for the... 

The latter two approaches are related because natural and artificial tracers are used to calibrate or evaluate ocean models. A key aspect of these tracers is that they provide independent information on timescale, either because they decay or are produced at some known rate, for example, due to radioactivity, or because they are released into the ocean with a known time history. The different chemical tracers can be roughly divided into two classes. Circulation tracers such as radiocarbon, tritium- He, and the chlorofluorocarbons are not strongly impacted by biogeochemical cycling and are used primarily to quantify physical advection and mixing... 

The missing carbon concept arose because radiocarbon-calibrated carbon cycle models predict that the quantity of carbon remaining in the atmosphere after fossU fuel release should exceed that suggested by the direct observation of rising concentrations of carbon dioxide. Three solutions have been proposed. One is that current ocean models cannot be adequately calibrated using radiocarbon. A second is that the biosphere currently acts as a sink for carbon. The third is that the biosphere has been a net source of carbon in the past. 

There are two main calibration curves, one for the atmosphere (currently IntCall3) and one for the oceans (Marine 13) with details published in Reimer et al. (2013). These latest curves cover the full effective range of the radiocarbon dating technique (50,000 years). 

When calibrating a radiocarbon date, it is first important to determine the reservoir from which the sample draws its carbon (Northern Hemisphere Atmosphere, Southern Hemisphere atmosphere, ocean, etc.). For the oceans, it is also necessary to know how different the local ocean radiocarbon levels are from the ocean average. A useful reference for this is the Marine Reservoir Database (http //calib.qub.ac.uk/marine/), which provides a compilation of preindustrial values. It should be noted, however, that changes in ocean circulation over time make these values inherently uncertain this is especially true when considering pre-Holocene dates. 

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