Suess Effect Research Articles

An anomalous Suess effect above Europe

The major impact that man is likely to have on climate comes from the artificial increase of the atmospheric CO2 level, caused by the combustion of fossil fuels1,2. To predict its magnitude, the future rise of the global atmospheric CO2 level must be calculated using carbon reservoir models. Because fossil fuel CO2 lacks 14C and has a 13C/12C ratio which is 18‰ lower than the present average atmospheric 13C/12C ratio, the validity of such geochemical models can be tested using past temporal variations in the atmospheric concentration of these isotopes. However, the past variation of the 13C/12C ratio in global reservoirs is very difficult to infer3. Using Δ14C data of tree rings Suess measured a depletion in the atmospheric 14C concentration over the past century of <10‰ (ref. 4). Some years later more accurate data gave a value for this ‘Suess effect’ of 15–25‰ (ref. 5). As the models have been improved considerably over the past few years6–8 the availability of Δ14C data with an accuracy of better than 1.5‰ was thought to be essential to test these9,10. The present results indicate a good correlation with model predictions taking into account natural 14C variations. However, deviations between American and European tree ring data after AD 1920 suggest a European continental CO2 effect.

Radiocarbon in annual coral rings from the eastern Tropical Pacific Ocean

Sixty radiocarbon measurements were performed on aragonite from annually banded corals collected from three sites in the Galápagos Islands. Preanthropogenic Δ14C values of coral that grew around A.D. 1930 averaged −70‰. This is substantially lower than average values previously reported (−51‰) for corals from Florida and Belize in the western North Atlantic Ocean. A decrease of 6‰ was noticed in coral that grew from 1930 to 1954. This decrease could be interpreted as a Suess effect in surface ocean water. The 100‰ increase in Δ14C for coral that grew from 1954 to 1973 is the result of bomb‐produced 14C that was introduced to the surface ocean waters. The 14C levels in corals that grew during El Niño years were considerably higher than those for normal years. These higher values are attributed to the absence of up welling at the equator during El Niño events.

Natural atmospheric 14C variation and the Suess effect

THE dilution of the atmospheric 14CO2 concentration by large amounts of fossil-fuel derived CO2 which do not contain any 14C is commonly called the Suess effect. Its magnitude can be calculated with the same geochemical models as the global carbon cycle that also predict the future rise of atmospheric CO2 to be caused by the combustion of fossil fuels. Validation of a CO2 predictive model with the Suess effect 14C data is important because these two phenomena have a common cause, and therefore register model responses at roughly the same frequencies. Measurements of the Suess effect yield values between −15‰, and −25‰ in Δ 14C (in 1950)1, while different model predictions also cover about this range2,3. The requirement that a model correctly reproduces the Suess effect becomes a strong constraint when the accuracy of the measurement is improved to better than 2‰. 14C measurements in tree rings to an accuracy of 1.2‰ are reported here. The results indicate that the natural fluctuations of atmospheric 14C as yet preclude determination of the Suess effect to the accuracy required by the models.

The Suess effect: 13Carbon- 14Carbon interrelations

The Suess Effect is a term which has come to signify the decrease in 14C in atmospheric CO 2 owing to admixture of CO 2 produced by the combustion of fossil fuels. This term is here extended, as a concept, to the shifts in isotopic ratio of both 13C and 14C in any reservoir of the carbon cycle owing to anthropogenic activities. To explain this generalized Suess Effect a four reservoir global model of the natural carbon cycle is developed in which isotopic fractionation and radioactive decay are fully taken into account. The model includes the cases in which the deep ocean is treated either as a single undifferentiated box model reservoir or is vertically differentiated with eddy diffusion governing the transport of carbon. Also, the governing equations are expressed with sufficient generality to apply simultaneously to both rare isotopes. In so far as possible, the model is expressed without approximation of the isotopic processes even though this leads to non-linear differential equations to describe the rates of change of rare isotopic carbon within carbon reservoirs. Linear approximations also developed and solved using the method of Laplace transforms. The sensitivity of the predicted Suess Effects to uncertainties in the assigned values of the model parameters is investigated in detail, including estimates of some of the effects of linearizing the governing equations. The approximation of Stuiver, in which the atmospheric Suess Effect is assumed to be 0.018 times the corresponding effect for 14C, is examined in detail and shown to arise when both isotopic fractionation and radioactive decay are left out of the model. This approximation, although correct as to order of magnitude, is found to be too imprecise to be recommended in modeling studies. As found in previous work, the predicted atmospheric Suess Effect for 13C for a given airborne fraction of industrial CO 2 is of similar magnitude whether the land biosphere has been a net source or sink of carbon during recent times. On the other hand, the corresponding effect for a surface ocean water is considerably smaller than otherwise if the land biosphere has been a source of CO 2 instead of a sink. The model is thus useful in indicating the need to consider isotopes in several reservoirs simultaneously. Although the emphasis is on formulating models rather than surveying and interpreting data, observational data are summarized and compared with model predictions. The oceanic data are seen to be too meager as yet to help settle the question of biospheric response to man's activities.

Glasgow University Radiocarbon Measurements IV

The following list and data presented previously (R., 1970, v. 12, p. 494–495) were obtained to investigate the transport of carbon between man and his environment (Harkness, 1970). These data constitute a study of contemporary variations of C14 concentrations viz., Suess effect and bomb effect, as reflected in the tissues and food chain of the population of the United Kingdom (Harkness and Walton, 1969).

A theoretical approach to the Suess effect

From a theoretical study of the production and distribution of fossil-fuel carbon dioxide released since the beginning of the Industrial Revolution calculations have been made of the resultant decreases in atmospheric carbon-14 specific activities (Suess effect). The calculations are based on recent advances in the assessment of parameters which control carbon circulation and a re-evaluation of the combustion rates of fossil fuels. Results show that the reduction in carbon-14 specific activities amounted to -0.5, -3.2 and -5.9 % in A. D. 1890, 1950 and 1969 respectively. Analyses of biospheric materials of known age show good agreement between the predicted and observed atmospheric carbon -14 concentrations although the possibility exists of a perturbation of natural origin. The incorporation of significant amounts of fossil fuel carbon into 1890 wood indicates the possibility of error in radiocarbon analyses based on the conventional modern reference material. The study also enables corrections to be made for the Suess effect to observations of carbon -14 activities of samples grown during the past century. Predictions of future consumption of fossil fuels have permitted evaluation of the approximate magnitude of the future Suess effect. The results imply that the effect will be of increasing importance, reaching about -23% by 2000 and -50 % by 2025. The Suess effect, which is in competition with the nuclear bomb effect, may therefore reduce atmospheric carbon -14 concentration to the natural level again by 1990. Future increase in atmospheric carbon dioxide levels could have significant climatological consequences, but the magnitude of these changes remains speculative.

Problems in Radiocarbon Dating at Teotihuacan

AbstractRadiocarbon dating is a useful tool in archaeological research, but the precision hoped for by some is not attainable because of the nature of the radiocarbon assay itself, possible contaminations, the Suess effect, and especially the peculiar nature of wood structure and growth. Wood and charcoal, unlike animal remnants, will not necessarily give the age corresponding to the time when the tree died or was cut; they will give only the age of the particular fragment used in the radiocarbon assay. If wood comes from the central portion of a large tree stem, there may even be several hundred years difference between its radiocarbon date and the date of the corresponding archaeological level. Such discrepancies are common in the recent finds at Teotihuacάn. Even the apparently erroneous date of 1474 ± 230 B.C. for Teotihuacάn can thus be explained. Other radiocarbon dates should also be evaluated with this in mind.

University of Pennsylvania Radiocarbon Dates IV

With one exception, the radiocarbon dates in this list were reported previously by Rainey and Ralph (1959). For discussions of the reliability of the dates, of the materials dated, and of the correspondence of the dates with estimated arctic chronologies, the reader is urged to refer to the original publication. The radiocarbon determinations were made over a period of several years. Those processed before 1956 were dated by the solid-carbon method and are so labeled; others, by the carbon-dioxide method. The age calculations are based on the average of several samples dated archaeologically and by tree-rings, corrected to zero age (Rainey and Ralph, 1959, p. 365). By this means the errors due to atmospheric depletion (Suess effect) and to past changes in radiocarbon concentration (de Vries, 1958; Willis, Tauber, and Münnich, 1960) have been minimized. The b.p. dates are calculated from A.D. 1957 (solid-carbon) and A.D. 1958 (carbon dioxide).